THE SURFACE OF THE EARTH
MAP SHOWING THE DISTRIBUTION OF LAND AND WATER
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LAND FORMS OF THE WORLD
The proportion of land to water upon the earth is as 27 to 72, or roughly one-fourth to three-fourths; the land covering fifty-three million square miles, the sea one hundred and forty-four million. The land consists of six great bodies called continents, and a multitude of small fragments called islands, which skirt the shores of the continents or dot the broad expanse of the sea.
THE DISTRIBUTION OF
LAND AND WATER
By far the greatest proportion of land is in the northern hemisphere, and in temperate latitudes. Broadly speaking, the northern hemisphere is the hemisphere of land, and the southern hemisphere is the hemisphere of ocean. The earth could be bisected in such a way that one hemisphere contained almost no land, while the other was composed almost equally of land and water.
LOCATION OF THE
CONTINENTS
The greater part of the land on the earth’s surface is grouped into two great hemispheres, the Old and the New World. The former and far larger of these consists of Eurasia in the north, separated by ill-defined boundaries from Europe to the west and Asia to the east, and of Africa in the south, united to Eurasia by the narrow neck of the isthmus of Suez. The hemisphere of the New World is divided into North America and South America, united by the long, narrow isthmus of Central America. The island of Australia is also reckoned as a continent. It is believed that an island continent, Antarctica, surrounds the South Pole. Of islands not reckoned as continents, the largest is the polar island of Greenland.
CERTAIN RESEMBLANCES OF
THE CONTINENTS
In comparing the continents, we at once notice certain resemblances. The first is the tapering to the south, which is seen in Greenland, North and South America, Africa, and Australia (Tasmania). Another is the southward-running peninsulas which characterize Europe and Asia. We may notice, too, that the general lines of the Old World, broad in the north, tapering in the south, resemble those of the New World, especially if we include Australia (Tasmania), and compare its position with that of South America. There is also a certain uniformity in the distribution of relief. Notice the so-called Mid-World and Pacific Mountain systems, which may be traced in the mountains of Central Europe, North Africa, Central Asia, the islands of the Pacific from Japan to New Guinea, and the lofty mountains of North, Central, and South America.
DIAGRAM SHOWING AVERAGE HEIGHT OF THE CONTINENTS
COMPARISON OF THE CONTINENTS
| Continent | Asia | Africa | North America | South America | Europe | Australia | All Land | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Area (million square miles) | 16 | .4 | 11 | .1 | 7 | .6 | 6 | .8 | 3 | .7 | 3 | .0 | 55 | .0 | ||
| Average Height (feet) | 3, | 000 | 2, | 500 | 1, | 900 | 2, | 000 | 940 | 800 | 2, | 100 | ||||
| Highest Point (feet) | 29, | 000 | 18, | 800 | 18, | 200 | 22, | 400 | 18, | 500 | 7, | 200 | 29, | 000 | ||
| Percentage at Various Altitudes (feet) | ||||||||||||||||
| Below Sea-Level | 1 | .4 | 0 | .1 | 0 | .05 | 0 | .0 | 1 | .8 | 0 | .0 | 0 | .6 | ||
| 0 | to | 600 feet | 23 | .3 | 12 | .5 | 32 | .25 | 40 | .0 | 53 | .8 | 29 | .8 | 26 | .7 |
| 600 | to | 1,500 feet | 16 | .0 | 34 | .8 | 32 | .1 | 26 | .8 | 27 | .0 | 64 | .3 | 27 | .8 |
| 1,500 | to | 3,000 feet | 21 | .7 | 27 | .6 | 13 | .3 | 16 | .8 | 10 | .0 | 4 | .1 | 19 | .3 |
| 3,000 | to | 6,000 feet | 21 | .8 | 21 | .8 | 13 | .2 | 7 | .0 | 5 | .5 | 1 | .5 | 17 | .0 |
| 6,000 | to | 12,000 feet | 10 | .0 | 2 | .8 | 8 | .4 | 5 | .0 | 1 | .7 | 0 | .3 | 6 | .0 |
| Above 12,000 feet | 5 | .8 | 0 | .4 | 0 | .7 | 4 | .4 | 0 | .2 | 0 | .0 | 2 | .6 | ||
THE SHAPING OF
THE COAST
The coast line, or margin of sea and land, is an area rapidly wearing away under the ceaseless influence of the waves, and of the sand and rock, they are perpetually hurling to and fro. Coasts may be either flat or high, composed either of hard or soft rock, and either submerged or raised. A submerged coast is one where the land has sunk or the sea has risen, so that the low grounds and valleys are flooded. A raised coast is one where the land has risen or the sea has retired, and what was formerly the sea bottom is bared.
A flat coast is usually sandy, often bordered by sandhills and lagoons. It may be carved into cliffs, as in the clay cliffs of Norfolk, England. A raised coast is usually flat from the long-continued action of the waves during the period when it was submerged. Flat coasts have no good harbors.
A submerged coast differs according to the nature of the submerged region. If this was hilly or mountainous, with valleys running parallel to the shore, the coast will be ironbound and harbor-less unless the sea-level has risen sufficiently to give access to the valleys behind the first range of heights. If this happens, T-shaped gulfs are formed. Where the valleys open at right angles to the sea, they become bays, usually with excellent harbors. The hills between the valleys rise as peninsulas, or islands. If the land was flat before submerging took place, a flat coast is the result.
Where the land is composed of soft rocks, a more uniform coast-line results than where it is composed of harder rocks, or of hard and soft rocks mixed. The waves, in eating out the softer rocks, often form magnificent sea-caves, natural arches, and pinnacles.
THE COASTLINE OF THE
VARIOUS CONTINENTS
Europe surpasses all the other continents in the magnitude of its indentations and projections. Three great peninsulas—the Balkan peninsula, Italy, and Spain, project into the Mediterranean; while Brittany, Denmark, and Scandinavia jut into the shores of the Atlantic. Even the British Isles are scarcely more than a projection of the continent.
Asia is a second in the relative extent of its peninsula. Asia Minor on the west, Arabia, India, and Indo-China on the south, and China, Manchuria with Corea and Kamchatka, advancing into the waters of the Pacific, form a wide border of projecting lands, containing the richest regions of the continent.
North America is considerably less indented. Florida, Nova Scotia and Labrador are more prominent on the Atlantic coast, and California Peninsula and Alaska on the Pacific.
The southern continents on the contrary, are nowhere deeply penetrated by the waters of the ocean. The Gulf of Arica in South America, the Gulf of Guinea in Africa, and the Great Australian Bight, are merely gentle bends in the coast line.
LOCATION OF THE GREAT
PLAINS OF THE WORLD
Plains occupy nearly one-half of the surface of the continents. They are most extensive and unbroken on the Arctic slopes of the Old World, and in the interior of the two Americas.
Treeless plains, whose vegetation consists of grasses and other herbaceous plants, or stunted shrubs, occur in every continent, and are designated by a variety of terms. Wherever treeless plains are subject to periodical rains, they lose their verdure in the season of drought, and assume the aspect of a desert; but they resume their freshness on the return of the rain, and many are adorned with a great variety of beautiful flowers.
Plains of the Old World. The great Siberian plain extends from the northeastern extremity of Asia to the Ural Mountains and Caspian Sea; and the European plain stretches from the Ural westward, through Russia and North Germany, to the lowlands of Holland.
The plains of the Caspian Sea and western Siberia are dreary steppes, covered with coarse grasses, often growing in tufts, alternating with patches of heather, furze, dwarf birch, and other stunted shrubs; or old sea bottom, covered with salt efflorescence. Immense reaches of flat country, near the Arctic shores of Asia and Europe, consist of frozen marshes, called tundras, where mosses and lichens are almost the only vegetation. Those of eastern Europe and Asia are denominated steppes; while more limited treeless regions in western Europe are called landes and heaths.
On the alluvial plains of the Old World, civilization began and developed; and their inexhaustible fertility supplied the wants of the most populous nations of antiquity. The great centers of ancient civilization in Egypt, China, India and Babylonia, all had their growth in alluvial plains, built up and fertilized by the mighty rivers which traverse those countries.
Plains of the New World. In North America the great Central Plain extends, with but slight interruptions, from the Arctic shores to the Gulf of Mexico. The fertile, treeless plains are termed “prairies” (meadows), while the sterile ones, east of the Rocky Mountains, are known as “the plains.” There are vast cane fields and forests in the lower Mississippi Valley.
In South America the plains of the Orinoco basin, the Selvas of the Amazon, and the Pampas of the La Plata, form an uninterrupted series of lowlands which, continued by the plains of Patagonia to the southern extremity of the continent, extend over a distance of three thousand five hundred miles from north to south. The Spanish term “llano” (plain), and the Peruvian “pampa,” designate the treeless plains of the Orinoco and La Plata basins. The Llanos of the Orinoco, during one-half of the year are covered by the richest pasturage, bright with flowers, but during the other half are a parched waste. The Selvas of the Amazon, a luxuriant forest, cover more than a million square miles; and the treeless Pampas, with their tall grasses and thickets of clover and thistles, illustrate the endless richness and variety of nature.
Alluvial and marine plains generally have but a slight altitude, while the undulating plains are sometimes considerably elevated. The Mississippi Valley, at St. Louis, one thousand miles from the ocean, is hardly four hundred feet above the sea-level; and the Amazon, at an equal distance from the sea, does not reach two hundred and fifty feet. The marine plains adjacent to the Caspian and Aral seas are still lower, the larger portion being below the sea-level.
SITUATION, ELEVATION AND
SOIL OF PLATEAUS
Plateaus are situated either between two lofty mountain chains, which form their margins, or descend by successive terraces to the nearest seas; or they pass, by gradations, from the base of high mountains to the low plains in the interior of the continents.
The Great American Basin, between the Rocky and Sierra Nevada Mountains, and the plateau of Tibet, between the Himalaya and Kuenlun mountains, are examples of the first position; and the table-land of Mexico, of the second. The third is seen in the high plains at the eastern foot of the Rocky Mountains, which descend from an altitude of five thousand or six thousand feet, at the foot of the mountains, to the low plains of the Mississippi basin.
The plateaus most remarkable for their elevation are, Tibet, from ten thousand to eighteen thousand feet above the sea; and the elongated valley-like highlands, from ten thousand to thirteen thousand feet high, between the two chains of the Andes, in South America. East Turkestan and Mongolia, in central Asia; the plateau of Iran, in western Asia; Abyssinia, and the vast plateau which occupies all the southern part of Africa; and the broad table-land which fills the western half of North America with a continuous mass of high land, range in height from four thousand to eight thousand feet.
The great peninsulas of Deccan, Arabia, Asia-Minor and Spain, the central plateau of France, and those of Switzerland, Bavaria, and Transylvania, vary from one thousand to four thousand feet in elevation.
SOIL AND CLIMATE
OF PLATEAUS
The nature of the soil and climate of great plateaus is in general such as to render them the least useful portions of the continents. Sahara, with an average altitude of 1,000 feet, and the higher plateaus of Mongolia, Iran and parts of the American Basin, may serve as types.
Their surface consists of hardened sand and rock; of hillocks and plains of loose sand constantly shifting by the wind; and of immense tracts, as in Mongolia, covered with pebbles varying from the size of a walnut, or even less, to a foot in diameter: all indicating the original transporting, grinding and depositing of these materials by water.
Salt lakes without outlet occur in each, and salt efflorescence often covers the ground. A lack of rain to wash from the soil substances injurious to vegetation, and supply the water necessary for the growth of plants, leaves these plateaus generally sterile, and some of the most extensive are in part, if not wholly, deserts.
MOUNTAINS AND THEIR STRUCTURES
Mountains rise in long and comparatively narrow lines or ridges, the tops of which are often deeply indented, presenting to the eye the appearance of a series of peaks detached one from another. As each of these peaks or distinct elevations is called a mountain and often receives a separate name, the common designation chain or range of mountains is naturally applied to the whole.
The top of the ridge, from which the waters descend on opposite sides, is called the crest; and the notches between the peaks, from which transverse valleys often stretch like deep furrows down the slopes of the chain, are called passes.
HOW MOUNTAIN CHAINS
FORM SYSTEMS
Mountain chains are seldom isolated, but are usually combined into systems, consisting of several more or less parallel and connected chains, with their intervening valleys,—as the Appalachian system, the Alps, and the Andes.
Most mountain chains seem to have been produced by tremendous lateral pressure in portions of the Earth’s crust, causing either long folds, or deep fissures with upturned edges rising into high ridges, the broken strata forming ragged peaks.
TWO TYPES OF MOUNTAIN
CHAINS
Mountains by folding are generally of moderate elevation, while mountains by fracture include the highest chains of the globe. The Appalachian Mountains in North America, and the Jura in Europe, are examples of the first; the Rocky Mountains, Andes, Alps and Himalayas, of the second.
Folded mountains are curved into long arches, either entire or broken at the summit and forming a system of long, parallel ridges, of nearly equal height, separated by trough-like valleys. Here and there, however, deep gaps, or gorges, cut the chains allowing the rivers to escape from one valley to another.
In systems of mountains produced by fracture, there is usually one main central chain, with several subordinate ranges. They have, however, less regularity and similarity among themselves than the parallel chains of mountains by folding.
The crests are deeply indented, cut down one-third or one-half the height of the range, forming isolated peaks and passes which present to the eye the appearance of a saw, called in Spanish Sierra; in Portuguese, Serra. Such ranges are frequently distinguished by these terms, as the Sierra Nevada, in North America; and the Serra do Mar, in Brazil.
HOW VALLEYS ARE
FORMED
Valleys among mountains owe their existence primarily to folds or fissures in the Earth’s crust, produced in the upheaving of the ranges; but they are subsequently deepened, widened and otherwise changed in form and extent, by the action of rains and frosts, and the streams to which they furnish a pathway. Most of the Alpine lakes, celebrated for their picturesque beauty, occupy deep basins at the outlet of transverse valleys.
Valleys in plains and plateaus are mainly, if not entirely, the result of the erosion, or wear of the surface, by running water.
Little rills, formed by the rains or issuing from springs, set out on their course down the slope of the ground, each wearing its small furrow in the surface. Uniting they form a rivulet which wears a broader and deeper channel; and the rivulets in turn combining, form rivers which produce still greater effects.
The great basin of the Mississippi for example, is one grand central valley, cut by the main stream in the line of lowest level, towards which the valleys of the Missouri, the Arkansas, the Ohio, and a multitude of smaller streams, all converge.
CELEBRATED MOUNTAIN PEAKS THAT STAND AS THE EARTH’S GREATEST SENTINELS
1. Mount Everest, the loftiest mountain in the world, is situated in Nepal, India, and rises to an ascertained height of 29,000 feet—almost six miles. It was named for Sir George Everest, an English engineer, and outline Surveyor-General of India. Everest is only one of numerous gigantic peaks of the Himalayas—often called the “Roof of the World”—and is apparently guarded against all attempts at ascent by a rampart of lofty pinnacles. It is best viewed from a point near Darjeeling, India, one hundred and twenty miles distant. From this point travelers are enthralled with the glistening peak of mountain piles as nowhere else on earth. Though a thousand times described, the view is so surpassingly sublime that its full glory can never be depicted in words.
2. Mont Blanc (mòn-blon-g) is the highest mountain in Europe, and of the Alps. It is located between Great and Little St. Bernard passes, on the frontier of France, Switzerland and Italy; and is best seen and approached from the village of Chamounix (shä-mo-nē´), France. It was first ascended in 1786, but frequently since, and, in 1893, an observatory was built on its summit. The Mont Blanc chain is famous for glaciers. Many great poets have described the majesty of Mont Blanc, among them, Goethe, Victor Hugo, Byron, Shelley, Wordsworth, and Coleridge.
3. The Matterhorn, or Mount Cervin, a splendid mountain obelisk, towers above Zermatt, Switzerland, on the Italian border. The eastern side seems almost vertical, and its ascent is very difficult; hence its name which is due to the formation of the rocky, horn-shaped peak. The loss of life attending its ascent has given the Matterhorn the grim name “Fatal Mountain.”
4. Monte Rosa (mŏn´te rō´sa), “rosy mountain,” is next to Mont Blanc, the highest Alpine peak. It is the border between Italy and Switzerland, sixty miles north of Turin, Switzerland. Unlike the Matterhorn, Monte Rosa is easy of ascent and is frequently climbed by ladies. Its name refers to the glaciers which abound and reflect beautiful colors.
5. Jungfrau (yung´frau), “virgin,” is one of the Bernese Alps, Switzerland, thirteen miles from Interlaken. It is so named from the pure whiteness of its snowclad peak. A wonderful mountain railway now reaches to the summit, most of the line being through tunnels. Jungfrau is 13,670 feet high.
6. Mount Elburz is one of the loftiest and most impressive of all the Caucasian mountains. It is an extinct volcano with two peaks, the western peak 18,470 feet above sea-level, and the other 18,347 feet. It is covered with glaciers, and constitutes a watershed which divides Asia from Europe. The Caucasus gave its name to that great branch of the human race that has ruled the world for many generations.
7. Mount Sinai (si´nā or -nī), famous as the sacred mountain on which Moses received the Ten Commandments, is an individual peak in a vast rocky mass that almost fills the peninsula of Sinai between the Gulf of Suez and Gulf of Akaba. It is named from Sin, the Babylonian moon-god. At its foot, in a ravine, is the monastery of St. Catherine, founded by the Emperor Justinian; a short distance from it the Chapel of St. Elias (Elijah); while on its summit is a little pilgrim church. Its height is 8,593 feet.
8. Pike’s Peak. This famous mountain is six miles from Colorado Springs, Colorado, and may be ascended by a cog railway. It is one of the best-known summits of the Rocky Mountains, and rears its snowy crest to a height of 14,134 feet. On its top is one of the highest weather stations in the world. The view from the observatory is superb, embracing thousands of square miles of mountain and plain.
9. Mount St. Elias, on the Alaskan side of the Canadian frontier, was long considered the highest peak in North America. It is a volcanic mountain, stands in a wild, inaccessible region, and is clothed almost from base to summit with eternal snow. Besides, there are huge glaciers, impassable precipices and yawning chasms. Its height is 18,020 feet. It was ascended by the Duke of the Abruzzi in 1897.
10. Mount Assiniboine (as-sin´i-boin) is frequently called the “Matterhorn of the Canadian Rockies”. It is 11,860 feet in height, and is located near the boundary of British Columbia and Alberta, about twenty miles south of Banff, in one of the most beautiful scenic regions in America. In the immediate vicinity there are geysers, caves, waterfalls, numerous lakes, natural bridges, and glaciers.
11. Mount Popocatepetl (pō-pō-kă-tā-pet´l) is one of the giant volcanic peaks standing guard over Mexico City. Its summit is perpetually covered with snow, but it may be ascended from Popo Park, the terminal of the railway which climbs its slope, to a height of 8,000 feet. The peak itself is 17,887 feet, at the apex of which is a huge crater sheathed with ice, from which clouds of vapor are continually ascending. No great eruption, however, has taken place since 1540. The most imposing spectacle of all from the summit is the remarkable formation of clouds below.
12. Mount Salcantay, one of the most beautiful peaks of the Andes, in Peru, is 21,000 feet in height. Its grandeur is enhanced by the presence of glaciers and the enveloping clouds. It rises to a sharp point with its sides covered with snow and ice, and lifts its head magnificently thousands of feet higher than the surrounding mountains. It has been recently explored by the Yale University expedition.
13. Mount Robson, the highest point in the Canadian Rockies, reaches an elevation of 13,700 feet. It is on the border between Alberta and British Columbia, one of the remarkable “show places” of the Canadian Rockies. All around it is the finest of scenery—huge mountains, snow-crested peaks, rushing rivers that swirl and foam, mysterious canyons and earth-strewn boulders.
14. Mount Rainier (rā´ner) an isolated mountain of the Cascade Range, forty miles southeast of Tacoma, Washington, is an extinct volcano, 15,529 feet in height. There are still two craters at the summit which give off heat and sulphurous fumes. Thick forests cover the lower region of the mountain, while higher up there are fourteen glaciers. It is difficult of ascent, though frequently made. A bridle path leads to a point over 7,000 feet in elevation from which a magnificent view of several of the glaciers may be had.
Mount Ararat, famed as the mountain where Noah’s ark landed after the flood, as recorded in Genesis, is in the Turkish province of Armenia. Ararat is really a twin mountain, the two peaks of which are about seven miles apart, with an elevation of about 17,000 and 13,000 feet, respectively. They rise above a beautiful alluvial plain, and quite naturally the higher peak—Great Ararat—is the one made historically immortal as the motherland of the human race. From their isolation and bareness the two peaks are very impressive, and it is little wonder that Armenia regards these mountain tops as a crown of glory and all other lands as her daughters. Within her borders, too, she gives rise to the beautiful rivers Euphrates, Tigris, Pison, Araxes, and many others. The first modern ascent of the mountain was made in 1829, though often since.
REMARKABLE CANONS OF THE ROCKY
MOUNTAIN PLATEAUS
Wonderful examples of valleys by erosion occur in the plateaus adjacent to the Rocky Mountains. The Grand Canon of the Colorado, three hundred miles long, has a depth of from three thousand to six thousand feet below the surrounding country. The sides of this tremendous gorge, which are nearly or quite precipitous, exhibit the successive geological strata down to the oldest rocks. A similar formation exists in the upper course of the Yellowstone, one of the main tributaries of the Missouri, and to a less extent in all the streams flowing through the high barren plateaus.
Valleys descending the slopes of mountains are formed in the same manner. The gathering drops make the rill, and the rill its little furrow; rills combine into rivulets, and rivulets make a gully down the hill-side; rivulets unite to form torrents, and these work with accumulating force, and excavate deep gorges in the declivities. Other torrents form in the same manner about the mountain ridge, and pursue the same work of erosion until the slopes are a series of valleys and ridges, and the summit a bold crest overlooking the eroding waters. The larger part of the valleys of the world are formed entirely by running water.
ISLANDS OF THE WORLD
CONTINENTAL AND OCEANIC
ISLANDS
The multitude of small and apparently fragmentary bodies of land, called islands, form only about one-seventeenth part of the entire land surface of the globe.
Continental islands are situated in the immediate vicinity of the continents, and form properly a part of the continental structure. They have the same kinds of rocks and mountain forms, and the same varieties of plants and large animals, which are found on the neighboring coasts of the mainland.
The size of this class of islands varies extremely. Some are mere isolated rocks, while others occupy large areas, like the British Isles, Japan Islands and Madagascar; or, more extensive still, Papua and Borneo, each of which has an area exceeding two hundred thousand square miles.
The distinctive character of Oceanic islands is that they lie at a distance from the continents, in the midst of the ocean basins. They are always small, and, though sometimes forming lines, or bands, they more frequently occur in groups.
The rocks which make up the body of the continents and continental islands—sandstone, slate, granite, and the various metamorphic rocks—are entirely wanting in oceanic islands. The latter are composed either of volcanic substances, or of limestone. Hence they present much less variety in relief forms than the continental islands.
FORMS OF VOLCANIC
ISLANDS
The islands of volcanic origin are more or less circular in outline; are usually considerably elevated, with rapid slopes; and are of moderate size. Sometimes two or more volcanoes, clustered together, form a single island of larger size and more irregular outline.
Occasional islands rise but little above the surface of the sea, their craters being filled by sea water. Many, however, rise to Alpine heights—like the peaks of Hawaii, in the Hawaiian Islands, nearly fourteen thousand feet in elevation; Pico de Teyde, in the Canaries, fourteen thousand feet; and Tahiti, in the Society Islands, over seven thousand feet above the level of the sea.
WONDERFUL STRUCTURE OF
CORAL ISLANDS
Coral islands are among the most striking phenomena of the tropical seas. Whitsunday Island in the midst of the Pacific is an excellent example. Rising but a few feet above the surface of the ocean, it forms a narrow, unbroken, nearly circular ring, surrounding a central lagoon of quiet water. When first seen, it presents the aspects of an angry surf breaking on a white beach of coral sand, in strong contrast with the deep blue color of the sea. Behind this a garland of luxuriant vegetation, whose tropical beauty, enhanced by the noble cocoa-palm encircles the quiet waters of the lagoon, while all around spreads the broad blue sea.
TWO OF THE GREATEST MARVELS OF LAND AND SEA
THE GRAND CANYON OF THE COLORADO RIVER, ARIZONA
This greatest of nature’s gorges is more than twelve miles across, a mile deep, and extends over two hundred miles in length. This whole vast space has been sculptured by the wear of the river through countless centuries. Its unparalleled magnitude, its architectural forms and suggestions, and its wealth of color effects create a picture that is grand beyond description.
THE BARRIER CORAL REEF OF AUSTRALIA
This vast reef of coral islands was built by a colony of coral insects, or polyps, as innumerable as the stars of the Milky Way. It rose from the floor of the ocean, builded out of myriads upon myriads of the dead skeletons of these marvellous insects.
COMBINATION OF VOLCANIC
AND CORAL ISLANDS
A large number of volcanic islands in the Pacific are encircled by coral reefs, which, when near the shore, are called fringing reefs. When at a considerable distance, leaving a lagoon of quiet water between them and the volcanic island, they are termed barrier reefs.
CORAL REEFS AND THEIR
BUILDERS
Coral reefs are masses of limestone originally secreted, in the form of coral, by minute polyps which live in countless numbers in the tropical seas. The coral produced by a single community of polyps grows chiefly upward; but multitudes of distinct communities often live so near together that the small lateral growth of each brings them into contact.
Their separate, fragile structures, gradually broken up and compacted by various means, are in time transformed into a solid mass, forming walls of coral rock frequently of enormous extent. The great barrier reef near the northeastern shores of Australia, the longest known, is not less than one thousand two hundred and fifty miles in length.
A LIVING SINGLE CORAL FROM THE PACIFIC OCEAN
The coral polyp is one of the master-builders of the world. It may be likened to a sea-anemone, but is inferior in muscular organism, and immensely superior in defensive organization.
Reef-building polyps do not live below the depth of one hundred or one hundred and twenty feet, and hence require a foundation near the surface. This is supplied by submarine mountains and plateaus, or the slopes of those volcanic cones which form the high islands.
Growing vertically, the reefs repeat at the surface the outlines of their bases, which fact gives rise to the circular figure both of atolls and reefs in mid-ocean, and to the elongated, wall-like form of reefs adjacent to the continents, like those of Florida and of Australia.
DISTRIBUTION OF
CORALS
Reef-building polyps are confined to the tropical seas, where the winter temperature is not below sixty-eight degrees. Coral formations are most extensive in the Pacific Ocean, especially south of the Equator, and in the two great archipelagoes of the East and West Indies; but a large number of coral islands also occur in the Indian Ocean. The Coral Sea, east of northern Australia, is particularly remarkable for the great extent of its coral reefs.
THE ATOLL FORM
OF ISLAND
The usual form of coral islands is that of a broken ring, numerous channels affording entrance into the lagoon. Such a group of islands is called an atoll, a Malay term, which has been adopted to designate these singular structures. The central lagoon enclosed by an atoll, is invariably shallow, seldom exceeding a few scores, or at most hundreds, of feet in depth; while the outer sea reaches a depth of thousands of feet at a short distance from the shore, showing that the atoll rests upon a submarine mountain.
Atolls are often clustered together in large numbers, forming extensive archipelagoes. Paumotu, or Low Archipelago, numbers eighty coral islands, nearly all of which are atolls; the Caroline, Gilbert and Marshall islands together contain eighty-four atolls, while the Laccadive and Maldive islands form two long double series of atolls extending eight hundred miles from north to south.
MAP SHOWING COMPARATIVE SIZE OF ISLANDS
(See [next page] for the Area, Population and Countries to which these islands belong).
ISLANDS OF WESTERN HEMISPHERE
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MOST NOTED ISLANDS OF THE WORLD—WESTERN HEMISPHERE
| Name and Sovereignty | Area Square Miles | Popula- tion |
|---|---|---|
| Anticosti (to Britain) | 2,600 | 500 |
| Bahamas (to Britain) | 4,404 | 58,000 |
| Bermudas (to Britain) | 20 | 20,000 |
| Cape Breton (to Britain) | 3,120 | 100,000 |
| Cuba (Independent) | 44,164 | 2,155,000 |
| Dominica (to Britain) | 291 | 35,000 |
| Falkland (to Britain) | 5,500 | 3,250 |
| Feeji, or Feejee (to Britain) | 7,435 | 155,000 |
| Galapagos (to Ecuador) | 2,400 | 400 |
| Greenland (to Denmark) | 46,740 | 15,000 |
| Guadeloupe (to France) | 688 | 182,000 |
| Hawaiian See [Sandwich]. | ||
| Isla de Pinos (Isle of Pines) (to Spain) | 1,200 | 32,000 |
| Jamaica (to Britain) | 4,200 | 865,000 |
| Long Island (to U. S.) | 1,682 | 2,700,000 |
| Martinique (to France) | 378 | 180,000 |
| New Foundland (to Britain) | 42,734 | 218,000 |
| Porto Rico (to U. S.) | 3,604 | 1,120,000 |
| Prince Edward (to Britain) | 2,184 | 94,000 |
| Santo Domingo (Independent) | 28,250 | 2,700,000 |
| Sandwich or Hawaiian (to U. S.) | 6,449 | 192,000 |
| Staten Island (to U. S.) | 65 | 86,000 |
| Tahiti (to France) | 1,500 | 30,000 |
| Tierra del Fuego (to Argentina) | 18,500 | 1,700 |
| Trinidad (to Britain) | 1,750 | 350,000 |
| Vancouver (to Britain) | 15,937 | 55,000 |
MAP SHOWING COMPARATIVE SIZE OF ISLANDS
ISLANDS OF EASTERN HEMISPHERE
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MOST NOTED ISLANDS OF THE WORLD—EASTERN HEMISPHERE
| Name and Sovereignty | Area Square Miles | Popula- tion | |||
|---|---|---|---|---|---|
| Balearic Islands (to Spain) | 1,935 | 326,000 | |||
| Borneo (to Britain and Holland) | 284,000 | 2,000,000 | |||
| Canary Islands (to Spain) | 2,807 | 420,000 | |||
| Candia, or Crete (to Turkey) | 3,365 | 243,000 | |||
| Cape Verde Islands (to Portugal) | 1,480 | 148,000 | |||
| Celebes (to Holland) | 71,470 | 2,000,000 | |||
| Ceylon (to Britain) | 25,332 | 3,595,000 | |||
| Corsica (to France) | 3,378 | 290,000 | |||
| Cyprus (to Britain) | 3,584 | 140,000 | |||
| Elba (to Italy) | 85 | 27,000 | |||
| England (Independent) | 88,729 | 40,835,000 | |||
| Formosa (to Japan) | 13,458 | 3,392,000 | |||
| Gothland (to Sweden) | 1,217 | 56,000 | |||
| Hainan (to China) | 16,000 | 2,000,000 | |||
| Iceland (to Denmark) | 39,756 | 86,000 | |||
| Ireland (to Britain) | 32,360 | 4,382,000 | |||
| Japan | - | Honshiu | 87,485 | 37,415,000 | |
| Khiushiu | 16,840 | 7,727,000 | |||
| Skikoku | 7,031 | 3,290,000 | |||
| Hokkaido (Yezo) | 36,299 | 1,140,000 | |||
| Java (to Holland) | 50,554 | 30,100,000 | |||
| Madagascar (to France) | 227,950 | 2,745,000 | |||
| Madeira Islands (to Portugal) | 314 | 150,600 | |||
| Malta (to Britain) | 117 | 229,000 | |||
| New Guinea See [Papua]. | |||||
| New Zealand (to Britain) | - | N. Island | 44,468 | 564,000 | |
| S. Island | 58,325 | 445,000 | |||
| Papua, or New Guinea (to Britain, Germany and Holland) | 313,183 | 710,000 | |||
| Philippines (to U. S.) | - | Luzon | 40,969 | 3,800,000 | |
| Mindanao | 36,292 | 500,000 | |||
| Panay | 4,611 | 744,000 | |||
| Cebu | 1,762 | 593,000 | |||
| Leyte | 2,722 | 358,000 | |||
| St. Helena (to Britain) | 47 | 3,520 | |||
| Sakhalin (Japan and Russia) | 29,000 | 30,000 | |||
| Sardinia (to Italy) | 9,306 | 854,000 | |||
| Sicily (to Italy) | 9,935 | 3,685,000 | |||
| Spitzbergen (to Norway) | 27,000 | ... | |||
| Sumatra (to Holland) | 165,000 | 3,200,000 | |||
| Van Diemen, or Tasmania (to Britain) | 26,215 | 197,000 | |||
| Zanzibar (to Britain) | 640 | 115,000 | |||
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MARVELS OF THE EARTH’S ROTATION, FORCES AND STRUCTURE
1. Midnight Sun Within the Arctic Circle. 2. The Geyser At Rest. 3. Picture Diagram of a Section through a Volcano like Vesuvius. 4. The Geyser in Action. 5. Section of the Earth’s Crust across France and Italy.
1. Precambrian or Archaean. 2. Cambrian and Ordovician. 3. Silurian. 4. Carboniferous Limestone. 5. Coal Measures. 6. Permian. 7. Trias. 8. Jurassic. 9. Chalk. 10. Tertiary. 11. Volcanic Rocks. 12. Glacial Deposits. 13. Granite. 14. Gneiss. 15. Schist. 16. Alluvium.
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VOLCANOES, GEYSERS AND EARTHQUAKES
THE REMARKABLE SUBMARINE VOLCANO OF SANTORIN (Săn-to-rē´n)
In this little Bay of Santorin, enclosed by an island of the same name in the Grecian Archipelago, occurred probably the most remarkable volcanic exhibition known. During an eruption in 1866 flames issued from the sea rising sometimes to a height of twenty-five feet, and a dense column of white smoke mounted to an immense height. Within a few days a new island appeared which gradually became united to the present Santorin.
CAUSE, STRUCTURE AND LOCATION OF VOLCANOES
The primary cause of volcanoes, as of geysers, earthquakes and other similar phenomena of nature, is the intensely heated condition of the earth’s interior. It is the same force that has produced the irregular features of the earth’s surface—its mighty mountain chains, the sunken basins of the oceans, and its hills, valleys and gorges. Quite logically, volcanoes are most numerous and most intense along the deep mountain fissures which establish a ready communication between the interior and the surface of the earth. Consequently the significant facts about them are: (1) Nearly all volcanoes are either along the highest border of the continents, or in the great central zone of fracture; (2) most of the volcanic groups exhibit a linear arrangement; (3) the agent at work in these mighty engines is mainly vapor of water, or steam power.
WHAT VOLCANOES ARE AND
HOW THEY ACT
The form of typical volcanic mountain is that of a cone, with a circular basin or depression, called a crater, at its summit. In the center of the crater is the mouth of a perpendicular shaft or chimney, which emits clouds of hot vapor and gases; and in periods of greater activity, ejects ashes, fragments of heated rock, and streams of fiery lava.
Volcanic ashes, when examined under a microscope, are found to be simply pulverized lava, frequently in minute crystals, and bear no resemblance to ashes in the ordinary sense of the term.
The lava stream, when flowing white hot from the crater, is not unlike a jet of melted iron escaping from a furnace, and moves at first with considerable rapidity. It soon cools on the surface, and becomes covered with a hard, black, porous crust, while the interior remains melted and continues to flow. If the stream is thick, the lava may be found still warm after ten or even twenty years.
The amount of matter ejected by volcanoes is very great. The whole island of Hawaii, the largest of the Hawaiian Islands, seems to be only an accumulation of lava thrown out by its four craters. All high oceanic islands are of the same character. Iceland, with an area of forty thousand square miles, is a vast table-land from three thousand to five thousand feet in elevation, composed of volcanic rock similar to the lavas still ejected by its numerous volcanoes.
VESUVIUS THE MOST
REMARKABLE VOLCANO
Nearly all active volcanoes have intervals of comparative repose, interrupted by periods of increased activity, which terminate in a violent ejection of matter from the interior, during which the volcano is said to be in a state of eruption.
The phenomena which characterize these differing phases of volcanic activity may be best made clear by describing them as actually observed in Vesuvius, one of the most carefully studied and most active volcanoes of modern times.
Vesuvius is a solitary mountain rising to the height of nearly 4,000 feet, from the midst of a highly cultivated plain which borders upon the shores of the Bay of Naples. Though the mountain has a regular conical form, two summits, very nearly equal in height, are visible from Naples—Monte Somma on the north, and Vesuvius proper on the south.
The Eruption begins generally with a tremendous explosion which seems to shake the mountain to its very foundations, and hurls into the air dense clouds of vapor and ashes. Other explosions succeed rapidly, and with increasing violence, each sending up a white, globular cloud of steam, or aqueous vapor. This long array of clouds, accompanied by dark ashes, volcanic sand, and fragments of red-hot lava of all sizes, soon forms a stupendous column.
Finally the boiling lava overflows the rim of the crater, and descends in fiery torrents down the slopes; or, bursting the mountain by its weight, finds a vent through some fissure far below the summit. After the expulsion of the lava the eruption is generally near its end, though it does not necessarily terminate at once. Alternate phases of outbursting steam, ashes, and lava may continue with more or less violence for weeks or even months.
The sudden condensation of the enormous accumulation of hot vapor thrown into the air by the eruption, gives rise to striking atmospheric phenomena. Vivid flashes of lightning start from all parts of the column, and play about the clouds above; and often a local thunderstorm, formed in the midst of a clear sky, pours a heavy rain of warm water and ashes upon the slopes of the mountain. The hot, destructive mud torrents, created by these rains, have often been mistaken for lava streams.
The majesty of the spectacle is still greater at night. Though flames of burning gases are of rare occurrence, the clouds and columns of vapor are strongly illuminated by the reflection of the white-hot lava within the crater; and fragments of this lava constantly thrown into the air give the column all the brilliancy of a gigantic piece of fire-work. The sky itself, far and wide, partakes of the same vivid coloring, and the whole scene resembles a vast conflagration.
SIZE AND DISTRIBUTION
OF VOLCANOES
In size they vary from mere mounds a few yards in diameter, such as the salses or mud-volcanoes near the Caspian, to Etna, 9,652 feet high, with a base thirty miles in diameter; Cotopaxi, in the Andes, 18,880 feet high; or Mauna Loa, in the Sandwich Isles, 13,600 feet high, with a base seventy miles in diameter and two craters, one of which, Kilauea, is the largest active crater in our earth, being seven miles in circuit.
Two great terrestrial zones include nearly all the known volcanoes of the globe, arranged in long bands or series, or in isolated groups.
First Zone. This includes the vast array of mountain chains, peninsulas, and bands of islands which encircle the Pacific Ocean with a belt of burning mountains. Within it occur, in the New World: (1) the Andes mountains, with three of the most remarkable series of volcanoes—those of Chili, Bolivia, and Ecuador—separated by hundreds of miles; (2) the volcanic group of Central America; (3) the series of Mexico; (4) the series of the Sierra Nevada and Cascade mountains; (5) the group of Alaska; and (6) the long series of the Aleutian Islands.
In the Old World are: (1) the series of Kamchatka and the Kurile Islands; (2) the group of Japan; (3) the series south of Japan, including Formosa, the Philippine and the Molucca Islands; and (4) the Australian series, including New Guinea, New Britain, New Hebrides, and New Zealand. In this vast zone there are not less than four hundred volcanoes, one hundred and seventy of which are still active.
Second Zone. This contains the belt of broken lands and inland seas, which extending round the globe, separates the northern from the southern continents, and intersects the first zone, in the equatorial regions, nearly at right angles.
In it are: (1) the volcanic regions of Central America and Mexico, and the series of the Lesser Antilles; (2) the groups of the Azores and Canary islands (3) the Mediterranean islands and peninsulas, including all the active volcanoes of Europe; (4) Asia Minor with numerous extinct volcanoes; (5) the shores of the Red Sea and Persian Gulf, and the two Indias, rich in traces of volcanic action; (6) the East Indian Archipelago with hundreds of burning mountains; and (7) the Friendly Islands and other volcanic groups of the central Pacific.
In this zone there are no less than one hundred and sixty volcanoes, so that the two volcanic zones together contain five hundred and sixty, or five-sixths of all known.
Isolated Volcanoes. The volcanoes not included in these two great zones are isolated, in the midst of the oceans, or in the broken polar lands. The most noted are the Hawaiian Island group, in the Pacific; Bourbon and Mauritius, in the Indian Ocean; Cape Verde Islands, Ascension, St. Helena, and Tristan da Cunha, in the Atlantic; Iceland and Jan Mayen, in the Arctic Ocean; and Erebus and Terror, in Antarctic.
MOST NOTED VOLCANOES
| Name | Location | Height (feet) |
|---|---|---|
| Altar | Ecuador | 17,710 |
| Antisana | Ecuador | 19,335 |
| Asosan | Japan | 5,630 |
| Cayambi | Ecuador | 19,255 |
| Chimborazo | Ecuador | 21,424 |
| Copiapo | Chile | 19,700 |
| Cotocachi | Ecuador | 16,300 |
| Cotopaxi | Ecuador | 18,880 |
| Demavend | Persia | 18,500 |
| Etna | Sicily | 9,652 |
| Fujiyama | Japan | 12,390 |
| Hecla | Iceland | 5,110 |
| Hood, Mt. | Oregon | 11,225 |
| Iztaccihuati | Mexico | 16,076 |
| Kirishima-yama | Japan | 5,530 |
| Llullaillac | Chile | 21,000 |
| Maipo | Chile | 17,670 |
| Mauna Kea | Hawaii | 13,953 |
| Mauna Loa | Hawaii | 13,600 |
| Misti | Peru | 20,015 |
| Nevado de Colima | Mexico | 14,210 |
| Orizaba | Mexico | 18,310 |
| Pelée | Martinique, W. I. | 4,300 |
| Pichincha | Ecuador | 15,918 |
| Pico, Peak of | Azores | 7,013 |
| Popocatepetl | Mexico | 17,748 |
| Ruiz | Colombia | 17,388 |
| Sahama | Peru | 23,000 |
| Sangai | Ecuador | 17,459 |
| San Jose | Chile | 20,020 |
| St. Elias, Mt. | Alaska | 18,024 |
| St. Helena, Mt. | United States | 10,000 |
| Stromboli | Lipari Islands | 3,090 |
| Tahiti, Peak of | Friendly Islands | 7,400 |
| Teneriffe | Canary Islands | 12,000 |
| Tolima | Columbia | 18,069 |
| Toluco | Mexico | 14,950 |
| Tunguragua | Ecuador | 16,690 |
| Vesuvius | Italy | 4,260 |
EARTHQUAKES
Earthquakes are movements of the earth’s crust, varying in intensity from a slight tremor or shaking of the ground to the most violent convulsions causing enormous destruction over wide areas.
KINDS OF MOTION OBSERVED
IN EARTHQUAKES
The wave-like or undulatory motion is most common and least destructive. It appears to be the normal one, and it is possible that the others may be simply the result of various systems of waves intersecting one another. The waves either advance in one direction, like waves of the sea, or spread from a central point, like ripples produced by dropping a pebble into still water.
The earthquakes of the Andes are chiefly linear, being propagated along the mountains, with the undulations perpendicular to the direction of the ranges. The destructive earthquake at Lisbon, was a central one, the concentric waves gradually diminishing in intensity with increasing distance from the place of origin.
The vertical motion acts from beneath like the explosion of a mine, and when violent nothing can resist its force. The earthquake at Calcutta, in September, 1828, owed its great destructiveness to the fact that the main shock was vertical; and one in Murcia, Spain, in 1829, destroyed or injured more than three thousand five hundred houses.
The rotary or whirling motion is the most dangerous, but happily the rarest of all. In the great earthquake of Jamaica, in 1692, the surface of the ground was so disturbed that fields changed places, or were found twisted into each other.
EARTHQUAKE SHOCKS
AND SOUNDS
Probably no part of the earth’s surface is entirely free from vibration, but, fortunately, destructive earthquakes are confined to comparatively limited regions. In most cases each shock lasts only a few seconds, but the tremblings that follow may be continued for days, weeks, or even months. Noises of sundry kinds usually precede, accompany, or succeed an earthquake. Some earthquakes, however, are not attended by any subterranean sounds. This has been the case with some of the most destructive South American disturbances. Thus at the time of the terrible shock which destroyed Riobamba in Ecuador in 1797, a complete silence reigned. On the other hand, subterranean sounds may be heard without any earth-tremor being perceived.
The sound which accompanies many earthquakes is due to the transmission to the air of vibrations in the soil. To produce sound-waves in the air, the ground must vibrate like a drumhead. Hence no sound will be heard when the oscillations are horizontal.
The velocity of propagation of an earthquake is very variable. Thus in the case of the earthquake of Lisbon in 1755, it seems to have considerably exceeded one thousand feet per second, while in the Lisbon earthquake of 1761 the rate was three times greater. At Tokio, in 1881, the velocity, as estimated by Professor Milne, varied between four thousand feet and nine thousand feet per second.
Depth of Earthquakes. Various attempts have been made to estimate the depth at which earthquakes originate. Mallet was of opinion that the centrum of the Neapolitan earthquake of 1857 was probably five and one-half miles from the surface. The same eminent physicist thought that an earthquake centrum probably never exceeded a depth of thirty geographical miles. According to Professor Milne, the angles of emergence of the earth-waves obtained during the Yokohama earthquake of 1880 showed that the depth of origin of that earthquake might be between one and one-half and five miles; and he gives a table, compiled from the writings of various observers, which exhibits the mean depths at which certain earthquakes have originated. These estimated depths range from 17,260 feet to 127,309 feet.
The area disturbed by an earthquake is generally proportionate to the intensity of the shock. The great earthquake of Lisbon disturbed an area four times as great as the whole of Europe. In the form of tremors and pulsations, Mr. Milne remarks, it may have shaken the whole globe.
In a violent submarine earthquake the ordinary earth-wave and sound-wave are accompanied by sea-waves. These waves may be twenty, sixty or even eighty feet higher than the highest tide, and are usually more dreaded than the earthquake shock itself in such regions as the maritime districts of South America. The greatest sea-wave on record is that which in 1737, is said to have broken near Cape Lopatka, at the south end of Kamchatka, two hundred and ten feet in height.
NOTABLY DESTRUCTIVE EARTHQUAKES
79. One accompanied by the eruption of Vesuvius; the cities of Pompeii and Herculaneum buried.
742. Awful one in Syria, Palestine, and Asia; more than 500 towns were destroyed and the loss of life surpassed all calculations.
936. Constantinople overturned; all Greece shaken.
1137. Catania, in Sicily, overturned, and 15,000 persons buried in the ruins.
1186. At Calabria; one of its cities and all its inhabitants overwhelmed in the Adriatic Sea.
1456. At Naples, 40,000 persons perished.
1537. At Lisbon; 1,500 houses and 30,000 persons buried in the ruins; several neighboring towns ingulfed with their inhabitants.
1596. In Japan; several cities made ruins, and thousands perished.
1662. One in China, when 300,000 persons were buried in Pekin alone.
1693. One in Sicily, which overturned fifty-four cities and towns, and 300 villages. Of Catania and its 18,000 inhabitants not a trace remained; more than 100,000 lives were lost.
1726. Palermo nearly destroyed; 6,000 lives lost.
1731. Again in China; and 100,000 people swallowed up at Pekin.
1746. Lima and Callao demolished; 18,000 persons buried in the ruins.
1754. At Grand Cairo; half of the houses and 40,000 persons swallowed up.
1755. Quito destroyed.
1755. Great earthquake at Lisbon. In about eight minutes most of the houses and upward of 50,000 inhabitants were swallowed up, and whole streets buried. The cities of Coimbra, Oporto, and Braga suffered dreadfully, and St. Ubes was wholly overturned. In Spain, a large part of Malaga became ruins. One-half of Fez, in Morocco, was destroyed, and more than 12,000 Arabs perished there. About half of the Island of Madeira became waste; and 2,000 houses in the Island of Mytilene, in the Archipelago, were overthrown. This awful earthquake extended 5,000 miles; even to Scotland.
1759. In Syria, extended over 10,000 square miles; Baalbec destroyed.
1783. Messina and other towns in Italy and Sicily overthrown; 40,000 persons perished.
1797. The whole country between Santa Fe and Panama destroyed, including Cusco and Quito, 40,000 people buried.
1840. Awful and destructive earthquake at Mount Ararat, in one of the districts of Armenia; 3,137 houses were overthrown, and several hundred persons perished.
1842. At Cape Haytien, St. Domingo, which destroyed nearly two-thirds of the town; between 4,000 and 5,000 lives were lost.
1851. In South Italy; Melfi almost laid in ruins; 14,000 lives lost.
1852. At Philippine Isles; Manila nearly destroyed.
1853. Thebes, in Greece, nearly destroyed.
1854. St. Salvador, South America, destroyed.
1854. Amasca, in Japan, and Simoda, in Nippon, destroyed; Jeddo much injured.
1855. Broussa, in Turkey, nearly destroyed.
1857. In Calabria, Montemurro and many other towns destroyed, and about 22,000 lives lost in a few seconds.
1858. Corinth nearly destroyed.
1859. At Quito; about 5,000 persons killed, and an immense amount of property destroyed.
1868. Cities of Arequipa, Iquique, Tacna, and Chincha, and many small towns in Peru and Ecuador destroyed; about 25,000 perished.
1883. Krakatoa island, between Sumatra and Java, East Indies, was the scene of a series of volcanic discharges in May to August, 1883, constituting the most tremendous eruption known to history. A cubic mile of rock material was hurled into the air, and the explosions were heard 150 miles away. Violent atmospheric disturbances and gigantic sea-waves, the latter causing great loss of life, estimated at more than 30,000. As a result of the explosion, the north part of the island, including its highest peak, altogether disappeared.
1886. Shocks throughout eastern United States; at Charleston, S. C, 41 lives and $5,000,000 worth of property lost.
1893. Islands of Zante and Stromboli, the former west of Greece, the latter one of the Lipari group, west of Calabria, Italy, severely shaken. Great loss of lives and property at Zante.
1906. Severe shocks in California wrecked San Francisco and adjacent towns, and caused the greatest fire in history, lasting two days. Great loss of life, and $300,000,000 of property destroyed; over 300,000 homeless. Stanford University buildings were damaged to the extent of $2,800,000, including the fine Memorial Church.
1906. At Valparaiso, Chile, causing great destruction of life and property.
1907. Large part of Kingston, Jamaica, destroyed.
1909. In Sicily and southern Italy, Messina and many towns and villages desolated. Appalling loss of life; thousands buried alive; the survivors homeless; one of the greatest earthquakes of modern times if not of all time.
GEYSERS
Geysers are eruptive hot springs found chiefly in volcanic districts, but particularly in the Yellowstone Park, Iceland, New Zealand, Tibet and the Azores. At intervals these fountains of hot water and steam sometimes rise to a height of two hundred feet. The eruptions occur at intervals varying from every hour to once a day.
All the geyser waters hold in solution a considerable quantity of silica. The highly heated water decomposes the felspar and other volcanic rocks, and becoming slightly alkaline with the soda or potash these contain, it is enabled to form a silicious solution. The silica taken up is deposited again round the mouth of the orifice. Minute plants termed algæ are known to live in the hot water, and to aid in throwing down the silica from solution to form the sinter deposits.
The cause of the periodical eruptions is probably to be found in the gradual increase of heat with the depth of the tube. In the middle and lower parts the temperature is far above the boiling-point (212° F.) at the ordinary pressure. But at last the lower portion rises to a position where the temperature is above the boiling-point at the pressure it there sustains, and then, flashing into steam, it hurls the column above into the air. After playing for a few minutes the water falls back into the basin, and remains quiet for a time.
WONDERFUL GEYSERS OF
THE YELLOWSTONE
The geysers of the Yellowstone region are probably the most picturesque and wonderful in the world. On the Firehole River alone there are probably fifty geysers, throwing columns of water to a height of from fifty to two hundred feet, while smaller jets rise occasionally to two hundred and fifty feet. The “Old Faithful” geyser, in this region, throws up a column of water six feet in diameter to a height of one hundred to one hundred and fifty feet, at intervals of about an hour. Near the north entrance to the National Park, also, are the hot springs of the Gardiner River; here the “White Mountain,” built up of terraces of white calcareous deposits, rises to a considerable height, with a diameter of one hundred and fifty yards at the top.
The geysers of Iceland are situated within sight of Mount Hekla and are the hottest springs in Europe. The principal geysers of this region are known as the “Great Geyser” or “Roarer,” and the “Stroker” or “Churn.”
The geysers of New Zealand attained celebrity chiefly on account of the beautiful terraces associated with them. Unfortunately, volcanic activity manifested itself throughout the region in 1886, resulting in the destruction of the terraces. The basins connected with these geysers, catching the overflow of water, are, like those of Yellowstone region, largely used by bathers, and are much resorted to by invalids.
The three localities mentioned are where geysers attain their highest development; but they also exist in many volcanic regions notably in Japan, South America, and the Malay Archipelago.
HOW THE EVER-MOVING WATERS OF THE EARTH GO ON THEIR MIRACULOUS JOURNEY FOREVER
The circulation of the waters of the earth is just as marvellous as that of the blood in the human body. First, it is drawn up from the sea by the sun and rises as vapor; the cool air condenses it first into cloud and then rain or snow; it runs together, forming springs and waterfalls and rivers; and finally it finds its way to the sea, where again the never-ending journey begins.
THE WATERS OF THE EARTH
THE WATERS UNDER THE EARTH
The underground lake in its magnificent setting of dazzling stone columns and stalactites in the Cheddar Caves, England. All these wonderful natural halls, chasms and snowy incrustations were formed by the age-long action of the water on the limestone rocks through which it filtered.
Water is found in Nature in three states or conditions—as ice, vapor or steam, and as simple water. These three forms have the same chemical composition—the substance being a compound of oxygen and hydrogen, represented by the formula H2O; but the physical condition depends entirely on its temperature. Under ordinary atmospheric conditions water is a solid below 32 degrees Fahrenheit; a gas above 212 degrees Fahrenheit, and a liquid between these temperatures.
The purest form of water which exists in nature is rain water, though this always contains a little oxygen and carbon dioxide dissolved from the air. To obtain pure water artificially, any ordinary water is distilled, when all the solids dissolved in it are left behind. River water and spring water always contain a small quantity of solid matter, the amount and nature of the dissolved solids depending on the nature of the rocks over which the water has flowed.
Geographically it may be considered under the four heads of springs, rivers, lakes, and the ocean, which taken together forms the hydrosphere of the earth.
WHERE SPRINGS HAVE
THEIR SOURCE
Springs, or the natural fountains of water, take their rise from reservoirs stored under ground. Water maintains a level, and hence the height to which a spring will rise depends on that of the level from which it is supplied. If the internal reservoir be on a hill, and the spring should gush out in a valley, the water may rise to a considerable height and form a natural fountain; but, on the other hand, if the reservoir be at some depth below the surface, the water may never reach the surface, and mechanical aid may be required to obtain it.
These internal reservoirs are in a great measure supplied by moisture derived from rain, snow, mist, and dew. The atmospheric water enters the earth through porous rocks, or by means of fissures, and continues to sink until arrested in its progress by rocks, such as clay, which will not permit the water to pass, or by faults which check it from spreading. The waters will then gush forth as a spring, of greater or less size, according to the supplies it may have received.
HOW MINERAL SPRINGS
ARE FORMED
All springs contain a certain portion of air and gas, and also some solid matter, usually in the form of salts. When these salts are abundant, mineral springs are the result, which may be classified according to the character of their several properties, as acidulous, chalybeate, sulphurous, saline, calcareous, and silicious.
Acidulous or acid springs are those surcharged with carbonic acid gas.
Chalybeate springs are those in which iron, in the form of carbonate or sulphate, is held in solution.
Sulphur, in the form of sulphureted hydrogen or sulphate of lime, is the distinguishing ingredient in Sulphurous springs.
Saline springs are of two kinds—brine and medicinal; brine when containing a greater or less amount of chloride of sodium or common salt, and medicinal when containing other salts, as sulphate of soda, etc.
Calcareous springs are those highly charged with the salts of lime, and which have the property of petrifying substances placed within their reach, and also of depositing their contents, forming the stalactites and stalagmites of caverns, etc.
Silicious springs are so called from holding silica or flint in solution. The last-named are all hot or thermal as well as mineral springs, deriving their heat either from the natural heat of the earth at great depths, or from volcanic action. When occurring near volcanoes, they are frequently charged with bitumen, petroleum, naptha, asphaltum, etc.
WHY WATER FLOWS FROM
ARTESIAN WELLS
An important class of artificial springs or wells is known as Artesian Wells. Where bent pervious beds of rock lie between two bent impervious beds, so as to make a basin-shaped depression, lower in the middle than at the edges, the rain which sinks into the pervious rock where it reaches the surface will begin to gather in the central part of the porous rock as in a reservoir.
If a hole be now bored in the hollow of the upper impervious bed till it reaches the water-bearing stratum, the water will flow out at the top. The water thus obtained may have fallen a distance of many miles several months previously, and if the gathering-ground be high the issue at the well may be forced by the pressure of the water behind to a considerable height.
FORMATION, CHARACTERISTICS AND
PECULIARITIES OF RIVERS
Rivers have their sources from springs or from the melting of accumulations of snow. They do not, however, receive their largest supplies from the actual summits of mountains, for copious springs are rarely met with in such situations, nor are glaciers formed on the highest points of mountains, but more usually on slopes of the upper mountain valleys. It is, accordingly, in the latter localities that many of the largest rivers take their rise.
Watershed. It not unfrequently happens that several rivers take their rise in one mountain ridge, some flowing in one direction, and others taking an opposite course. Such a ridge is termed a watershed. Thus the Rhine, the Rhone, and the Danube all take their rise in the Alps, the first discharging itself into the North Sea, the second into the Mediterranean Sea, and the last into the Black Sea.
Basin. The portion of country drained by a river and its tributary streams is called its basin, from its catching the rains which fall within its circuit, and which the river carries to the sea. The largest river-basin in Europe is that of the Volga, in Asia, that of the Ganges, in Africa that of the Nile, in North America that of the Mississippi, and in South America that of the Amazon.
THE GREAT RIVERS OF THE WORLD
Deltas and Estuaries. Owing to local peculiarities at the mouths of rivers, accumulations of sedimentary matter take place in the middle of the stream, dividing it into two or more branches. By these depositions deltas (so called from the Greek letter (Δ) delta) are formed—many of them, as those of the Mississippi and Orinoco and of the Rhine and the Ganges, being of great extent. Some rivers fall into the ocean through estuaries or wide channels, and are subject to a great swell or sudden rise of the waters when the tide enters.
PICTURE DIAGRAM GIVING A COMPARATIVE VIEW OF
THE WORLD’S FAMOUS RIVERS AND MOUNTAINS
FIRST: Showing the comparative length of the rivers; where and how they take their rise; where and how they empty; their chief branches and connected lakes; and the principal cities located on their banks.
SECOND: Comparative height of mountains, arranged in groups by continents, showing the relative height of both mountains and continents. See [next page] for LOCATION and HEIGHT IN FEET of the various mountain peaks.
Large illustrations:
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[Moutains (left-hand side)] (187 kB)
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Most rivers are subject to an occasional, and in some instances to a periodical increase of volume. These seasons of flood are by no means regular, being partly dependent on the melting of the snows, and partly on occasional heavy falls of rain; and hence depend on the climatic variations of the country in which rivers originate.
FAMOUS MOUNTAIN AND OTHER ELEVATIONS OF THE WORLD
Note: The numbers refer back to the Picture Diagrams on the [preceding page].
FRESHWATER AND
SALT LAKES
Lakes are of different kinds. Some are mere tanks which receive the first outpourings of springs, others consist of basins or reservoirs which occur in the line of a river’s course; some consist of basins or cavities, into which rivers flow, but which, on account of their depression or their mountainous cincture have no outlets; lakes are also formed in the craters of extinct volcanoes; and some lakes are periodic, or subject to have their basins alternately empty and full of water.
Mountain Lakes, which are valleys or chasms filled by streams, are long and narrow, rarely of extensive area, but often of great depth. Examples of this class are found in Lakes Champlain and George, among the Appalachian Mountains; Lakes Constance and Geneva, on the northern side of the Alps; and Lake Maggiore and Lake Como, on the south side; all of which are renowned for the loveliness of their shores, or the grandeur of the surrounding mountain scenery.
Lake Maggiore, which is hardly three miles wide, is, according to Italian engineers, 2,623 feet deep—more than double the depth of Lake Superior—its basin reaching 1,936 feet below the sea level.
The forms of mountain lakes are very irregular, for the water often covers several contiguous and connected valleys. This is the case in Lake Como, which has two long arms; and Lakes Lucerne and Lugano, each of which fills four distinct valleys, meeting one another nearly at right angles.
Lakes in Plains. The lake basins in plains and plateaus are, usually, simple depressions in a comparatively uniform surface. The lakes are, therefore, often of great size, broad in proportion to their length, but of little depth compared with their area.
The largest lakes of the globe—the Caspian and Aral seas, and the great North American and African lakes—and the largest in Europe and South America, all belong to this class. Their vast expanse, together with the tameness of their shores, deprives them of the picturesque beauty of mountain lakes.
Characteristics of Salt Lakes. Numerous lakes in the interior of the continents, though receiving affluents, have no outlet. Their waters are chiefly lost by evaporation, though some portion may be absorbed by the sandy soil.
The surfaces of the continents having been the beds of the primeval oceans, the presence of salt in the soil is a natural consequence.
Famous Salt Lakes. The Great Salt Lake of Utah, in the Great American Basin, is one of the finest examples of its class. The Caspian and Aral seas, at the bottom of the vast depression between Europe and Asia, are the most extensive salt lakes. The former has about four times the area of Lake Superior; and the latter is a little larger than Lake Michigan.
The Caspian, though receiving the Volga, the largest river of Europe, evaporates so much water that its surface is about 83 feet lower than that of the Mediterranean, varying with the seasons. Many lakes in its neighborhood disappear entirely in the heat and drought of summer, leaving their beds covered with a crust of pure white crystalline salt.
The Remarkable Dead Sea, in Syria, is a lake in which the salt has accumulated until the water is converted into a heavy brine. It may be the remnant of an ancient sea of much greater extent, which has been gradually reduced in size by the excess of evaporation over the supply of water in its basin.
This celebrated body of water lies in the deepest part of a long chasm or valley, which is sunk not less than 4,000 feet below the level of the surrounding country. The surface of the lake is 1,286 feet, and its bottom 2,500 feet, below the level of the Mediterranean.
Its feeder, the river Jordan, flows almost throughout its entire course below the level of the sea, the only known instance of the kind. The beautiful lake of Tiberias, the scene of so many of the miracles of Jesus, which is but an expansion of the Jordan in its upper course, is about 650 feet below the surface of the Mediterranean.
HOW THE LAKES ARE DISTRIBUTED
OVER THE GLOBE
Lakes are most numerous in the central and northern portions of Asia, Europe and North America. The southern continents, except Africa, have comparatively few.
Asia is pre-eminently the continent of salt lakes. They occur in countless numbers, both in the steppes north of the Caspian and Aral, and in all the interior plateaus. Lakes of fresh water are also found among the Altai Mountains and adjacent chains. Lake Baikal, one of these, is the largest mountain lake known, being nearly 500 miles long.
Europe. The most characteristic and celebrated lakes are those which adorn the Alps of Switzerland and Scandinavia, and the less lofty mountain chains of the British Isles. But the largest lakes are found in the low lands and slight swells which surround the Baltic Sea, in western Russia and Sweden. Lakes Ladoga and Onega in Russia, and Wener and Wetter in Sweden, are the largest in Europe.
North America is peculiarly rich in great lakes. No continent presents a more remarkable series than that which stretches from northwest to southeast, through the central plains, along the line of contact of the oldest geological formations of the continent. This series includes Great Bear and Great Slave lakes, Athabasca and Winnipeg, and the five great lakes of the St. Lawrence, with many of less area.
Innumerable small lakes are scattered throughout the middle portions of the central plain, and the northern and less regular part of the Appalachian mountain region; but south of the parallel of Lake Erie there is an almost entire absence of lakes, whether large or small.
Relative Size of Lakes of the Western Hemisphere
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PRINCIPAL SALT-WATER LAKES OF THE WORLD
| NAME | Location | Area in Square Miles | Mean Elevation in Feet | |
|---|---|---|---|---|
| Black Sea | Asia and Europe | 170,000 | Sea-level | |
| Caspian Sea | Asia | 170,000 | 90 | below sea-level |
| Sea of Aral | Asia | 26,160 | 157 | above sea-level |
| Balkash | Asia | 7,135 | 779 | above sea-level |
| Maracaibo | South America | 6,315 | 0 | above sea-level |
| Eyre | Australia | 3,600 | 70 | above sea-level |
| Titicaca (slightly saline) | South America | 3,200 | 12,506 | above sea-level |
| Issik-kul | Asia | 2,250 | 5,300 | above sea-level |
| Great Salt Lake | North America | 2,177 | 4,218 | above sea-level |
| Koko-nor | Asia | 2,040 | 9,970 | above sea-level |
| Urumiah | Asia | 1,795 | 4,100 | above sea-level |
| Van | Asia | 1,400 | 5,200 | above sea-level |
| Dead Sea | Asia | 444 | 1,290 | below sea-level |
| Ngami (nearly dried up) | Africa | 297 | 2,919 | above sea-level |
Relative Size of Lakes of the Eastern Hemisphere
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PRINCIPAL FRESH-WATER LAKES OF THE WORLD
Africa. The great plateau lakes are typical of the continent. The Victoria Nyanza and Albert Nyanza, feeding the White Nile; Tanganyika, whose outlet is unknown; Tzana, at the head of the Blue Nile; and Lake Nyassa, in the Zambezi basin, all rest on the high plateaus of Central Africa. Lake Tchad alone, among large African lakes, is surrounded by low plains.
Waterfalls and Rapids. The variations in the slope of a river-bed, arising from unequal erosion, or from the original irregularities in the surface, give rise to rapids and falls.
The first occur where an increased slope causes the stream to flow with more than its average velocity. The second are caused by nearly perpendicular rocky walls, down which the foaming water descends in picturesque cascades, or imposing cataracts.
The famous “Cataracts of the Nile” are merely rapids which impede but do not entirely obstruct, the navigation as cataracts must. The so-called Falls of St. Anthony, in the upper Mississippi, and the rapids of the St. Lawrence, above Montreal, are among the finest rapids in American rivers.
The highest falls are in the upper course of rivers, in mountainous regions; the greatest and most imposing, in their middle course.
The Niagara Falls exhibit a most important industrial utilization of water power. The Falls of St. Anthony in the Mississippi, the Falls of Foyers in Scotland, the Rhine falls, the Rhone falls of Bellegarde, and the innumerable waterfalls of Scandinavia, Switzerland, and similar mountainous lands, are all utilized in this way. It has been proposed to convey power generated at the Victoria falls of the Zambezi to the Rand goldfield of the Transvaal, and a scheme for this is now being prepared.
FAMOUS WATERFALLS OF THE WORLD
| Name | Location | Height (feet) |
|---|---|---|
| Bridal Veil | California | 900 |
| Foyers | Great Britain | 205 |
| Gastein Falls | Austria | 469 |
| Gavarnie | Pyrenees | 1,400 |
| Genesee | New York | 95 |
| Grand Falls | Labrador | 2,000 |
| Great Falls | Montana | 500 |
| Hay River | Alaska | 200 |
| Kaieteur Falls | Guiana | 740 |
| Krimmler Falls | Austria | 1,300 |
| Kukenam Fall | Guiana | 1,500 |
| Maanelvan | Norway | 940 |
| Minnehaha | Minnesota | 50 |
| Missouri | Montana | 90 |
| Montmorenci | Quebec | 265 |
| Multnomah | Oregon | 850 |
| Murchison | Africa | 120 |
| Nevada Falls | California | 600 |
| Niagara | New York | 165 |
| Oroco Falls | Monte Rosa | 2,400 |
| Rjukanfos | Norway | 804 |
| Roraima Fall | Guiana | 2,000 |
| Rukaufos | Norway | 513 |
| St. Anthony | Minnesota | 80 |
| Schaffhausen | Switzerland | 100 |
| Seven Falls | Colorado | 266 |
| Shoshone | Idaho | 210 |
| Skykjefos | Norway | 700 |
| Snoqualmie | Washington | 268 |
| Staubbach | Switzerland | 1,000 |
| Stirling | New Zealand | 500 |
| Sutherland | New Zealand | 1,904 |
| Takkakaw | British Columbia | 1,200 |
| Tequendama | Colombia | 475 |
| Tessa Falls | Austria | 541 |
| Twin | Idaho | 180 |
| Velino Falls | Italy | 591 |
| Vermafos | Norway | 984 |
| Vettisfos | Norway | 950 |
| Victoria Falls | Zambezi | 400 |
| Voringsfos | Norway | 600 |
| Yellowstone (upper) | Montana | 110 |
| Yellowstone (lower) | Montana | 310 |
| Yguazu or Iguazu | Brazil | 210 |
| Yosemite (upper) | California | 1,436 |
| Yosemite (middle) | California | 626 |
| Yosemite (lower) | California | 400 |
FAMOUS WATER PICTURES OF THE NEW AND OLD WORLD
Niagara in winter presents a picture of frozen grandeur equaled nowhere else in the world.
The Rhine at Schaffhausen, Switzerland, rushes over rugged rocks on its way down from the highlands into the lovely and historic valley it has carved for itself on its way to the sea.
FAR-FAMED WATERFALLS THAT HAVE INSPIRED TRAVELERS AND WRITERS
1. The Niagara Falls and rapids form one of the most impressive spectacles in the world. The Niagara River, which is the sole outlet of the great lakes, pours itself in two vast sheets over a precipice about 160 feet high. Goat Island, which is situated on the lip of the falls, divides the cataract into two sections—the Horseshoe, or Canadian fall, which is by far the more majestic, and the America fall. It has a descent of 158 feet and the American fall of 167 feet. The volume of water which sweeps over this immense chasm is about 15,000,000 cubic feet per minute. The limestone edge of both falls is wearing away in the center, the Canadian fall now being V-shaped, and the American fall showing the same tendency, although its process of recession has begun more recently. For some distance below the falls there is smooth current, the mass of water which pours over the precipice sinking and only coming to the surface two miles below, where the rapids, more magnificent and wilder than those above the falls, begin, and culminate in the rapids of the Upper Whirlpool. Lower down the river is the whirlpool itself, where a sharp turn sends the waters hurling against the Canadian side; they then sweep round in a gigantic circle before they find a vent at right angle with their former course. The sight of the falls is equally awe-inspiring from the bridge on the lip of the fall, from the boat which plies from shore to shore below the cataract, or from the Cave of the Winds, reached from Goat Island. Although in summer the magnificence of the sight is extraordinary, it is in winter, when the wizardry of the frost is upon it, that it is superlatively beautiful. The falls were first discovered by Father Hennepin in 1678.
2. The Falls of Juanacatlan (hoo-ă-nă-kwt-lăn), Mexico, are located near the island city of Guadalajara (guă-dă-lă-hă´ră) on the Rio Grande de Santiago. Though only 70 feet in height they are more than 600 feet wide, and as known as the “Niagara” of Mexico.
3. The Cataracts of Iguazu (e-gwă´soo) on the frontiers of Brazil, Argentina and Paraguay. These falls, situated in a remote wilderness, far from civilization, are a veritable fortress in protecting the peace-loving peoples on their borders. They constitute a series of falls extending over three miles, and more than 200 feet in height, and of magnificent scenic beauty. Their energy is estimated to be about 14,000,000 horse-power, or almost three times that of Niagara.
4. The Yosemite (yo-sem´i-tee) Falls of California, are highest and probably the most remarkable of their class. They descend on almost perpendicular ledge of rocks 2,600 feet high to the bottom of the Yosemite valley, forming three separate cataracts. The first fall is 1,600 feet sheer descent. Then comes a series of cascades, partly hidden, 600 feet downward, and a final leap of 400 feet. Seen from afar, the Yosemite Falls seem insignificant; but they are, in fact, 35 feet wide, and the shock of their descent is observed a mile away.
5. The Staubbach (stoub´băk) Falls, in the Swiss Alps near Lauterbrunnen, descends a precipice of 980 feet, and is reduced to spray like a misty veil before reaching the bottom. It is the highest unbroken fall in Switzerland, and the most noted.
6. The Great Falls of the Yellowstone, though not so high, vie with the Yosemite in striking beauty. These famous falls plunge from a height of 360 feet into the abyss of a mighty chasm. At the point of descent, the waters of the Yellowstone suddenly contract from a width of 250 feet to 75 feet.
7. The Bridal Veil Falls of California, belong to the famous Yosemite Valley. Its waters, over 30 feet wide, leap from the granite rocks on the south wall of the Yosemite in two vertical descents aggregating over 900 feet. The first fall covers a distance of 600 feet, then the waters rushing over a sloping pile of jagged rocks drops a perpendicular distance of 300 feet more. From the chief points of view it seems to make but one plunge, in an unbroken descent similar to the Staubbach, but carrying a much greater volume of water. Frequently the wind swings the great plume of water from the face of the cliff and waves it like a scarf or veil. At sunset rainbows with an indescribable radiance bejewel its foam and the glistening leaves surrounding it.
8. The Reichenbach (ri´ken-băk) Falls near Meiningen, Switzerland, comprise five fine cascades in the Reichenbach River. The most gorgeous of these, known as the Upper Fall, makes a huge leap of 300 feet into a deep rocky basin, which then continues in several foaming and plunging cascades in general aspect not unlike the Niagara gorge.
THE OCEANS OF THE WORLD AND THEIR MYSTERIES
THE LAND AND WATER HEMISPHERES
The Oceans consist of one great fluid mass, and in extent covers three times the area of the dry land. There is also about three times as much land to the north of the equator as there is to the south of it. Though the waters of the ocean surround the land on every side, yet they are broken up into certain areas by the arrangement of the land portions, and to these various parts we give particular names.
The Atlantic Ocean, lying between the western shores of Europe and Africa and the east coast of America.
The Pacific Ocean, lying between the west coast of America and the east coast of Asia.
The Indian Ocean, lying between the south of Asia and the Antarctic circle.
The Arctic Ocean, lying within the Arctic circle.
The Antarctic Ocean, lying within the Antarctic circle.
VAST EXTENT OF
THE OCEANS
The Atlantic is the most branching of the oceans, and is especially distinguished by the number and great size of its inland seas. Two of these, the Mediterranean Sea and the Gulf of Mexico, lie in the warm regions; and two, Hudson Bay and the Baltic Sea, in colder latitudes.
The broader seas are represented by the Caribbean Sea, within the tropics and the Gulf of St. Lawrence and the North Sea in temperate latitudes. The Gulf of Guinea, and the Bay of Biscay, are examples of the more shallow coast waters.
The Pacific is particularly rich in vast border seas, a continuous series of which lines the Asiatic and Australian coasts. Among these are the Behring Sea, enclosed by the peninsula of Alaska and the Aleutian Islands; Okhotsk Sea, enclosed by Kamchatka and the Kurile Islands; the Sea of Japan, and the North and South China seas; and the Arafura, Coral, and New Zealand seas, on the Australian Coast.
Only two inland seas of considerable size—the Gulf of California in North America, and the Yellow Sea in Asia—mark this entire basin.
The Indian Ocean is characterized by gulfs, two of which form the entire extension of the basin; namely, the Gulf of Bengal, and the Arabian Sea. It has also two inland seas of considerable extent, the Red Sea and the Persian Gulf, isolating the peninsula of Arabia from the adjacent continents; but border seas are wholly wanting in the Indian Ocean.
The Arctic Ocean is a partially enclosed sea, which a comparatively inconsiderable rise of the sea-bottom would convert into a true Mediterranean. Three openings connect it with the Pacific and Atlantic Oceans, namely, Behring Straight (narrow and shallow), Davis Straight, and the broad expanse of water lying between Norway and Greenland. Of these, the last is by far the most important, for through it the warm waters of the Gulf Stream find access to the Polar basin, and keep the sea free from ice throughout the year. This current is supposed to flow feebly along the coast of Siberia, until, deflected by the land, it becomes merged in the cold counter-currents which, passing along the eastern coasts of Greenland and Labrador, carry immense masses of ice into the Atlantic.
PICTORIAL DIAGRAM OF THE STRUCTURE OF THE EARTH IF THE WATERS WERE REMOVED
Ridges, mountains, plateaus, which may represent submerged continents of the past, and many an abyss that exceeds in depth the height of the highest mountains, are shown above. The shallow coasts, marked by the lightest shade, are part of the present Continental Shelf, and do not exceed six hundred feet in depth. Beyond this shelf, as a rule, the oceans rapidly attain great depths. Our knowledge of the ocean bed has been obtained from the extensive soundings.
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The Antarctic Ocean is situated about or within the antarctic circle. The great Southern Ocean is that part of the ocean which surrounds the world between the latitude of 40 degrees south and the antarctic circle. The northern portions of this band are often called the South Atlantic, South Indian and South Pacific, while the southern portions are usually called the Antarctic Ocean. The average depth of the continuous ocean which surrounds south polar land is about two miles; it gradually shoals toward antarctic land, which in some places is met with a short distance within the antarctic circle. Life is abundant in the surface waters, and at the bottom of the ocean.
HOW THE FLOOR OF THE
OCEAN APPEARS
As a rule the sea is shallowest near the land, though in a few cases there is a sudden descent to a great depth at a very short distance from the coast. Lowlands have usually shallow seas near the coast, and highlands deep water.
Along the American shores, in the latitude of New York, the depth, for a distance of more than 100 miles, is less than 600 feet; then suddenly the bed descends, by a steep slope, to the depth of 6,000 or 9,000 feet. After a comparatively narrow interval, a second terrace descends to the main basin, from 15,000 to 18,000 feet deep.
The bottom of the trough of the ocean, in general, is equally varied with that of the land surface of the globe, forming mountains, hills, valleys, tablelands, etc. In many parts these marine mountains reach above the surface and form islands. On the table land extending across the Atlantic between Newfoundland and Ireland is laid the submarine-telegraph cable which connects the two hemispheres.
The Depth of the Oceans. The average depth of the Pacific Ocean has been estimated at between 15,000 and 18,000 feet, which is slightly greater than that of the Atlantic. The deeper portions may be learned on reference to the [map]. The western portion of the North Pacific in particular shows some very deep depressions. To the east of Japan lies a long deep trough which in one part has furnished the sounding of nearly five and one-half miles. This abyss is often called the Tuscarora Deep. South of the Ladrone Islands, in the Caroline Archipelago, there is also a deep abyss where an English ship, the Challenger, obtained a sounding of nearly 27,000 feet. In the Pacific soundings of over 30,000 feet have been made.
The Indian Ocean has an average depth of about 12,000 feet, and the deepest soundings have been taken on the eastern side. It is interesting to observe that the deepest sounding, about five and three-quarter miles, in the South Pacific somewhat exceeds the height of the highest mountain. Mount Everest has a height of 29,000 feet above the sea level. And it must also be noted that the mean height of the land, 1,000 feet, is only about one-twelfth the mean depth of the whole ocean, 12,000 feet. (See [colored map] showing comparative surfaces of land areas and ocean depths.)
Inland and Border Waters. These enclosed basins belong to the structure of the continents, rather than to the oceans. All are shallow in comparison with the great basins with which they are connected, as is apparent from the depths given below.
The Gulf of Mexico is from 5,000 to 7,000 feet in depth. The deepest part of the Caribbean Sea, on a line connecting Porto Rico and Costa Rica, averages 7,000 feet, and near the latter it reaches a depth of 14,000; but the ocean, immediately outside of the Lesser Antilles, is more than 18,000 feet deep.
The Mediterranean is divided into two basins, by a rocky isthmus, from 50 to 500 feet below the surface, lying between Sicily and Cape Bon, in Africa. The western basin is over 9,000 feet in depth, and comparatively uniform; while the eastern is more irregular, varying from 6,000 near the center, to 13,000 feet, south of the Ionian Islands. The Red Sea has an irregular bottom, with an average depth of 3,000 feet, but in some places it reaches 6,000.
The Baltic Sea, being a simple depression in the great European plain, is but a few hundred feet deep. In the North Sea, the depth averages 300 feet, and rarely exceeds 600. The continent is here prolonged in the form of a submarine plain, whose highest portions form the British Isles.
The Border Seas of Asia, lying within the chain of continental islands, are only a few hundred feet in depth, while immediately without those islands, abrupt slopes descend to the great depths of the Pacific basin.
Smaller inlets are also of frequent occurrence, especially in districts where mountain ranges approach the borders of the ocean. Such are the lochs of Scotland, the voes of the Shetland Islands, and the fiords of Norway and Greenland. The term lagoon is usually applied to lake-like inlets.
Salt and Other Ingredients of Sea-water. The waters of the ocean are salt, holding in solution various saline matters. The saline ingredients amount to rather more than thirty-five grains in a thousand grains of sea-water. The most abundant of these is chloride of sodium or common salt, which in general forms about a third of the whole. Besides this, sea-water contains some magnesia, lime, potash, and traces of iodine and bromine.
The following table exhibits the exact percentage composition of sea-water.
One hundred parts by weight of sea-water contain:
| Water | 96.470 |
| Sodium Chloride | 2.700 |
| Magnesium Chloride | .360 |
| Potassium Chloride | .070 |
| Magnesium Sulphate | .230 |
| Calcium Sulphate | .140 |
| Calcium Carbonate | .003 |
| Magnesium Bromide | .002 |
| Traces of Iodides, Silica, etc., estimated | .025 |
| 100.000 |
How the Sea gets its Color. The color of sea-water is due to the character of the skies and clouds above, and to vegetable and animal objects growing and living in it. The luminosity or phosphorescence of the ocean is due to the decay of animal and vegetable substances, but in some cases it arises from the presence of myriads of living animals, which, like the glow-worm and fire-fly of the land and air, have the power of emitting light.
Ocean Temperature. The water of the ocean appears generally to agree with that of the climate in which it is situated. In warm latitudes the temperature of the deep sea diminishes with the depth below the surface until a certain depth is reached, below which it appears to retain an equable temperature, this being about 40 degrees Fahrenheit. In the Polar Seas, where the temperature of the surface is lower than 40 degrees the heat increases downward until it reaches that point. In latitude 70° the temperature of the ocean is considered to be the same at all depths.
HOW TIDES ARE FORMED BY ACTION OF THE MOON
The moon pulls the waters of the earth into a great double wave heaping it up on the side nearest to the moon and on the opposite side. As the earth rotates, this double wave moves round the earth, and the crests and troughs alternately produce high and low tide. Thus there are two high and two low tides daily, at intervals of about twelve hours, or half a Sun or day.
CAUSE OF THE TIDES, WAVES AND
CURRENTS OF THE OCEANS
The waters of the ocean are retained in their bed by the attraction of gravitation. This power is great in proportion to the mass; and as the earth is of much greater mass than the particles of water on its surface, it attracts them and keeps them in their assigned places. But the sun and moon also possess this power of attraction, and notwithstanding their distance, attract and draw them up to a certain elevation. The vast mass of the waters being drawn up by the moon into a mountain or curve of water forms what is called the “great primary or tidal wave.”
VAST OCEAN CAVERN AT CAPRI, WIDELY KNOWN AS THE “BLUE GROTTO”
This remarkable cavern, on the shore of the island of Capri, at the entrance of the Bay of Naples, is entered from the sea, and is one hundred and eighteen feet long and forty feet high, with a breadth of ninety-eight feet at its widest part. It derives its name from the wonderful blue reflection of the sun’s rays through the water, which gives the interior its marvelous beauty and majesty. The cavern has been created by the ceaseless action of the tide.
Ebb-tide and Flood-tide. This drawing up of the waters of mid-ocean causes a recession from the shores, thus giving rise to ebb-tide, or low water. But when the temporary attraction ceases the waters flow back to their natural level, returning to shore and forming flood-tide, or high water. This culmination or rising of the waters in the great tidal wave takes place twice in twenty-four hours and fifty minutes. The combined influence of the sun and moon at new and full moon augments the size of this wave, and causes the “spring-tides” at those periods.
Height of Tides. High water at the various points along the coast is dependent on the return of this great wave, though some variations are caused by local peculiarities; and the height of the tide also varies greatly in different parts of the earth.
On the eastern coast of North America, the average rise of the tide is from nine to twelve feet. At the entrance to the Bay of Fundy, however, it rises eighteen feet, while at the head of that bay it reaches sixty, and in the highest spring tides, even seventy feet. At Bristol, in England, the spring tides rise to forty feet; and at St. Malo, on the south coast of the English Channel, they reach fifty feet.
THE MAELSTROM, CHARYBDIS
AND HELL GATE
Differences in level, produced by high tides, cause currents which vary in force and direction with the condition of the tide, producing, in some cases, dangerous whirlpools. The famous Maelstrom, off the coast of Norway, is but a tidal current, which rushes with great violence between two of the Lofoden Islands, causing a whirling motion in the water which is reversed at each ebb and flow of the tide.
Such is, also, the famous whirlpool of Charybdis, in the Straight of Messina, and many others of less note. The powerful currents of Hell Gate, in the passage from Long Island Sound to New York Bay, are due to a similar cause, high water occurring at different hours in the bay and in the west end of the sound.
WHAT CAUSES THE WAVES
OF THE OCEAN
The waves of the ocean, which are caused by the action of the wind, and which are called secondary or wind waves are of a totally different character from the tidal wave. The influence of the wind is supposed not to extend to a greater depth than forty or fifty feet, the deep sea, though raised in a great mass by the grand tidal movement, being free from agitation. Wind waves at a distance from the shore are comparatively low and long, but in shoal water they assume a greater curvature, and fall on the beach either in gentle ripples or in mighty breakers, according to the depth of the water and the force of the wind. The heavy swell which occasionally takes place, called the “ground sea,” is supposed to originate in distant storms of wind.
THE RIVERS IN
THE SEA
Currents in the ocean arise from various causes. They may be produced by long-continued gales of wind, by the melting of polar ice, or by any cause that may give rise to onward movements of limited portions of the great mass of waters. Other currents, and of these only is it necessary to speak in this connection, are permanent. The most remarkable of these are the polar currents and the equatorial currents.
Polar Currents are produced by the perpetual movement of the waters from the poles to the equator. In accordance with the laws of mechanics, an accumulation of the waters takes place on that part of the globe which has the greatest velocity of motion; and as the earth in turning on its axis moves with far greater velocity at the equator, the waters continually flow toward that line from the poles.
Equatorial Currents. This accumulation of the waters at the equator tends to produce the equatorial currents, which consist of the continuous progression of the tropical seas in a westerly direction. When the wave brought by the polar currents arrives—coming as it does from regions where it naturally has less velocity—it does not at once acquire the velocity of the earth’s motion at the equator; and since the rotation of the earth is from west to east, this portion of the water lagging behind forms a stream or current which has an apparent motion from east to west, that is to say, apparent as regards the earth, but real in relation to the adjacent land and water. The trade winds, which in this zone blow constantly in the same direction, lend their aid in maintaining the equatorial current.
THE GREAT SYSTEMS OF
OCEAN CURRENTS
An extensive system of currents appears to arise in the Antarctic Ocean. A current of cold water flowing northward joins the equatorial current in the Pacific. Entering the Indian Ocean, it maintains its westerly course until it approaches the shores of Africa; then bending southward it rushes through the Mozambique Channel, and doubling the Cape of Good Hope travels northward until it arrives at the Bight of Benin. This current then joins the equatorial current, and crossing the Atlantic from the coast of Guinea to that of Brazil, it is divided into two branches by the projecting headland of Cape San Roque, one flowing southward and the other northward.
The Gulf Stream. After passing the Island of Trinidad, this great oceanic current enters the Gulf of Mexico, and there acquires a high temperature, and sweeping round that sea it again pours forth into the Atlantic, forming the most powerful of known currents, called the Gulf Stream. Issuing from the Gulf of Mexico, this current of warm water rushes with considerable force through the Bahama Channel; then taking a northerly course it travels along the eastern shores of North America, and at Newfoundland is turned to the eastward by an opposing cold current which sets in from Baffin’s Bay. It now maintains an easterly direction, and crossing the Atlantic arrives at the Azores in about twenty-eight days, and divides its waters on the coast of France and Spain: one portion goes southward and at length joins the grand current which sets from the coast of Guinea; and another portion travels northward and skirts the western coasts of Europe. These currents are seldom more than 500 feet deep.