The changes briefly indicated above take place so gradually for the most part that it requires careful observation and comparison of data to establish their reality. It is very different with those changes which we usually ascribe to volcanic Volcanoes and earthquakes. agency. Besides the great outlying “hearth” of Iceland, there are four centres of volcanic activity in Europe—all of them, however, situated in the Mediterranean. Vesuvius on the western coast of Italy, Etna in the island of Sicily, and Stromboli in the Lipari group, have been familiarly known from the earliest historic times; but the fourth has only attracted particular attention since the 18th century. It lies in the Archipelago, on the southern edge of the Cyclades, near the little group of islets called Santorin. The region was evidently highly volcanic at an earlier period, for Milo, one of the nearest of the islands, is simply a ruined crater still presenting smoking solfataras and other traces of former activity. The devastations produced by the eruptions of the European volcanoes are usually confined within very narrow limits; and it is only at long intervals that any part of the continent is visited by a really formidable earthquake. The only part of Europe, however, for which there are no recorded earthquakes is central and northern Russia; and the Alps and Carpathians, especially the intra-Carpathian area of depression, Greece, Italy, especially Calabria and the adjoining part of Sicily, the Sierra Nevada and the Pyrenees, the Lisbon district and the rift valley of the upper Rhine (between the Vosges and the Black Forest) are all regions specially liable to earthquake shocks and occasionally to shocks of considerable intensity. One well-marked seismic line extends along the south side of the Alps from Lake Garda by Udine and Görz to Fiume, and another forms a curve convex towards the south-east passing first through Calabria, then through the north-east of Sicily to the south of the Peloritan Mountains.[14] Of all European earthquakes in modern times, the most destructive are that of Lisbon in 1755, and that of Calabria in 1783; the devastation produced by the former has become a classical instance of such disasters in popular literature, and by the latter 100,000 people are said to have lost their lives. Calabria again suffered severely in 1865, 1870, 1894, 1905 and 1908.

If the European mountains are arranged according to their greatest elevations, they rank as follows:—(1) the Swiss Alps, with their highest peaks above 15,000 ft.; (2) the Sierra Nevada, the Pyrenees, and Etna, about 11,000 ft.; (3) Relief. the Apennines, the Corsican Mountains, the Carpathians, the Balkans, and the Despoto Dagh, from 8000 to 9000; (4) the Guadarrama, the Scandinavian Alps, the Dinaric Alps, the Greek Mountains, and the Cevennes, between 6000 and 8000; (5) the mountains of Auvergne, the Jura, the Riesengebirge, the mountains of Sardinia, Majorca, Minorca, and the Crimea, the Black Forest, the Vosges, and the Scottish Highlands, from 4000 to 6000.

The following estimates are based on those contained in the fifth edition, by Dr Hermann Wagner, of Guthe’s Lehrbuch der Geographie. In the original the figures are given in German sq. m. and in sq. kilometres in round numbers, and the equivalents here given in English sq. m. are similarly treated:—

Sq. m.
The great European plain in its widest sense2,660,000
The same exclusive of inland seas2,300,000
The same exclusive of the Scandinavian and
  British lowlands2,125,000
All other European lowlands385,000
  The Hungarian plain38,000
  The Po plain21,000
The Scandinavian highlands190,000
The Ural Mountains127,000
The Alps85,000
The Carpathians72,000
The Apennines42,500
The Pyrenees21,500

Several estimates have been made of the average elevation of the continent, but it is enough to give here the main results. In the following list, where a conversion from metres into feet has been necessary, the nearest multiple of 5 ft. has been given:—Humboldt, 675 ft.; Leipoldt,[15] 975 ft.; De Lapparent,[16] 960 ft.; Murray,[17] 939 ft.; Supan,[18] 950 ft.; von Tillo,[19] 1040 ft.; Heiderich,[20] 1230 ft.; Penck,[21] 1085 ft. The exceptionally high estimate of Heiderich is due to the fact that by him Transcaucasia and the islands of Novaya Zemlya, Spitsbergen and Iceland are reckoned as included in Europe.

Of more geographical significance than these estimates are the facts with regard to the arrangement of the highlands of the continent. It is indeed this arrangement combined with the form of the coast-line which has indirectly given to Europe Arrangement of the highlands. its individuality. Three points have to be noted under this head:—(1) the fact that the highlands of Europe are so distributed as to allow of the penetration of westerly winds far to the east; (2) the fact that the principal series of highlands has a direction from east to west, Europe in this point resembling Asia but differing from North America; and (3) that in Europe the mountain systems belonging to the series of highlands referred to not only have more or less well-marked breaks between them, but are themselves so notched by passes and cut by transverse valleys as to present great facilities for crossing in proportion to their average altitude. The first and second of these points have special importance with reference to the climate and will accordingly be considered more fully under that head. The second is also of importance with reference to the means of communication, to which the third also refers, and detailed consideration of these points in that relation will be reserved for that heading. Here, however, it may be noted that in Europe the distribution of the natural resources for the maintenance of the inhabitants is such that, if we leave out of account Russia, which is almost entirely outside of the series of highlands running east and west, the population north of the mountains is roughly about 50% greater than that south of the mountains, whereas in Asia the population north of the east and west highland barrier is utterly insignificant as compared with that to the south.

Name of River. Length in English Miles. Area of Basin
in sq. m.
Strelbitsky. Other
Authorities.		 Strelbitsky.
Volga 1977[22] 2107[23] 563,300
Danube 1644 .. 315,435
Ural 1446 1477[23]  96,350
Dnieper (Dnyepr) 1064 1328[23] 203,460
Kama 984 1115[23] 202,615
Don (Russia) 980 1123[23] 166,125
Pechora 915 1024[23] 127,225
Rhine 709 ..  63,265
Oka 706 914[23]  93,205
Dniester (Dnyestr) 646 835[23]  29,675
Elbe 612 ..  55,340
Vistula 596 646[23]  73,905
Vyatka 596 680[23]  50,555
Tagus 566 ..  31,865[24]
Theiss (Tisza) 550 ..  59,350
Loire 543 ..  46,755
Save 535 ..  37,595
Meuse 530 ..  12,740
Mezen 496 507[23]  30,410
Donets 487 613[23]  37,890
Douro 485 ..  36,705
Düna (S. Dvina) 470 576[23]  32,975
Ebro 470 ..  38,580[24]
Rhone 447 ..  38,180
Desna 438 590[23]  33,535
Niemen (Nyeman) 437 537[23]  34,965
Drave 434 ..  15,745
Bug (Southern) 428 477[23]  26,225
Seine 425 ..  30,030
Oder 424 ..  17,150
Kuban 405 509[23]  21,490
Khoper 387 563[23]  23,120
Maros 390 ..  16,975
Pripet 378 404[23]  46,805
Guadalquivir 374 ..  21,580[24]
Pruth (Prutŭ 368 503[23]  10,330
Northern Dvina 358 447[23] 141,075
Weser-Werra 355 ..  19,925
Po 354 ..  28,920[24]
Garonne-Gironde 342 ..  32,745
Vetluga 328 464[23]  14,325
Pinega 328 407[23]  17,425
Glommen 326 352[25]  15,930
Bug (Western) 318 450[23]  22,460
Guadiana 316 ..  25,300[24]
Aluta (Alt, Oltŭ) 308 ..  9,095
Mosel 300 ..  10,950
Main 300 ..  10,600
Maritsa 272 ..  20,790
Jucar 270 ..  7,620[24]
Mologa 268 338[23]  15,005
Tornea 268 ..  13,045
Inn 268 ..  9,825
Saône 268 ..  8,295
Moldau 255 267[25]  10,860
Moksha 249 371[23]  19,090
Ljusna 243 ..  7,700
Mur 242 ..  5,200
Morava, Servian 235 ..  15,715
Klar 224 ..  4,520
Voronezh 218 305[23]  7,760
Berezina 218 285[23]  9,295
Saale 215 ..  8,970
Onega 212 245[23]  22,910
Vág (Waag) 212 ..  6,245
Dema 209 275[23]  4,830
San 203 444[23]  6,135
Moskva 189 305[23]  5,910
Western Manych 176 295[23]  37,820
Klyazma 159 394[23]  15,200

From the table given on p. 909 (col. 1) it will be seen that the most extensive of the highland areas of Europe is that of Scandinavia, which has a general trend from south-south-west to north-north-east, and is completely detached by seas and plains from the highland area to the south. There are other completely detached highland areas in Iceland, the British Isles, the Ural Mountains, the small Yaila range in the south of the Crimea, and the Mediterranean islands. The connected series of highlands is that which extends from the Iberian peninsula to the Black Sea stretching in the middle of Germany northwards to about 52° N. In the Iberian peninsula we have the most marked example of the tableland form in Europe, and these tablelands are bounded on the north by the Cantabrian Mountains, which descend to the sea, and the Pyrenees, which, except at their extremities, cut off the Iberian peninsula from the adjoining country more extensively than any other chain in the continent. Between the foot-hills of the Pyrenees, however, and those of the central plateau of France the ground sinks in the Passage of Naurouse or Gap of Carcassonne to a well-marked gap establishing easy communication between the valley of the Garonne and the lower part of that of the Rhone. The highlands in the north spread northwards and then north-eastwards till they join the Vosges, but sink in elevation towards the north-east so as to allow of several easy crossings. East of the Vosges the Rhine valley forms an important trough running north and south through the highlands of western Germany. To the south of the Vosges again undulating country of less than 1500 ft. in elevation, the well-known Burgundy Gate or Gap of Belfort, constitutes a well-marked break between those mountains and the Jura, and establishes easy communication between the Rhine and the Saône-Rhone valleys. The latter valley divides in the clearest manner the highlands of central France from both the Alps and the Jura, while between these last two systems there lies the wedge of the Swiss midlands contracting south-westwards to a narrow but important gap at the outlet of the Lake of Geneva. Between the Alps and the mountains of the Italian and Balkan peninsulas the orographical lines of demarcation are less distinct, but on the north the valley of the Danube mostly forms a wide separation between the Alps and the mountains of the Balkan peninsula on the south and the highlands of Bohemia and Moravia, the Carpathians and the Transylvanian Alps on the north. The valleys of the Eger and the Elbe form distinct breaks in the environment of Bohemia, and the Sudetes on the north-east of Bohemia and Moravia are even more clearly divided from the Carpathians by the valley of the upper Oder, the Moravian Gate, as it is called, which forms the natural line of communication between the south-east of Prussia and Vienna.

An estimate has been made by Strelbitsky of the length and of the area of the basins of all the principal rivers of Europe. In the table on p. 909 all the estimates given without any special authority are based on Strelbitsky’s figures, but it should Rivers. be mentioned that the estimates of length made by him evidently do not take into account minor windings, and are therefore generally less than those given by others. The authorities are separately cited for the originals of all other figures given in the table.[26]