My experiments with volcanoes

by Thomas Augustus Jaggar

A question arises as to how much the Grand Canyon itself and its tributaries are guided by fault fractures under valleys. My impression was in 1901, and it still is, that “Jaggar ought to teach faulting” more than he then did.

The primitive ocean blocks of earth crust sank, while continents remained high, leaving the earth crust a mosaic of blocks large and small, high and low. Between the blocks spout the volcanoes. I have never agreed with C. E. Dutton that volcanic heat energy could come from shallow pockets under those fault blocks. Even he acknowledged the weakness of the argument. If the earth crust broke up and the blocks variously sank in the core matter, leaving continents as a complex of high blocks, then the blocks are deep and are still moving. The movements are in years, year-thousands and year-millions. Volcanism up the cracks releases core energy. So does much of fault movement, namely earthquakes. And these facts geologists do not appreciate.

So we get faulted river courses and fault cracks up which came fluids that transformed sediments of rivers, lakes, deserts, and seas into granite, felsite, and greenstone. These are the ancient names. There are hundreds of other, geology names. But geology produced no Faraday.

I disliked geology in 1902. And I disliked mining because of its secrecy and its devotion to profits. Geology failed to tell businessmen the mystery of granite, of felsite, and of greenstone. Astronomers told the same men of mysteries, and they were fascinated. Physiology led them to cells, plants, animals, and chemicals in the blood, solving mystery after mystery. Men, money, inventions, engineers, buildings, and staffs grew by leaps and bounds in those sciences. The best geology could do was guesswork—a mastodon, a big reptile skeleton, a guesswork color map—while seventy percent of the earth was seabottom rock, unmapped, and twenty percent more consisted of fractures covered with soil.

Seeing the Carnegie and Rockefeller laboratories and observatories, I grieved for field geology. The public did not even know that granite, the mystery, is the commonest rock and that quartz, the gold maker, is the commonest mineral. Nor did they know that both are almost absent from the whole Pacific. Nor that geology is almost ignorant of their origin and injection, if it is injection. Here was the globe, the end product of astronomy, the most fascinating research in the whole range of science. The source of all raw materials of commerce, yet its fire-made rocks and its seabottom rocks remained a mystery.

Before leaving the Grand Canyon, let me record my impressions of the erosion. It is a gorge a mile deep usually described as “cut” by the Colorado River. As I shall show in discussion of experiments with the Grand Canyon model, it is possible, in stratified layers yielding grit to flowing rainwater, to cut a deep canyon by surface runoff. It is possible for underground water and tributaries from side rainfalls to increase the volume of such a stream greatly in a hundred miles. But Dutton’s showing of upheaved and downdropped big blocks of broken mountains, and such obvious breaks as the Tonto and Bright Angel faults shown to tourists as traced out by Bright Angel Canyon, prove that the earth crust is broken. And Searchlight showed a fault to be a water supply.

The enormous canyon appeared to me to be a million-year break system of earth-crust rotting. The water is a giant modern grinding mill of rainfall, underground accumulation, and transport. But with five great erosion surfaces shown in the discordances, from 2,000 million years ago to the present day; and with upheaval of the high plateaus in block faults, and bent strata age after age; and farther north with recent volcanoes that spouted up the cracks, it seems more vivid to think the valleys at least partly water-filled cracks and chasms. Volcanoes cannot be shallow. The canyons and the great bend are different from the Green River source, because of upward push in waves. The up-push of the Uinta Mountains is well known to have been slow. It kept pace with the ruptures followed by the river. Going back to Daubrée, rivers follow cracks much more than do the textbooks.

In 1899 two things happened which affected the rest of my life. First, Director Walcott asked me to furnish estimates for a Hawaii geologic survey, a request which eventually led me to Hawaii. Second, the Yakutat Bay earthquake snapped on an astonished world, though most of the world didn’t know it.

The Yakutat Bay earthquakes in Alaska, in September 1899, were accompanied by the pushing up of the bedrock shoreline by forty-seven feet. Lowered beneath the sea were whole forests, on glacial deposits pulled down by submarine landslips. It was an uninhabited region at the foot of Mount St. Elias, along a fjord penetrating far into the mountains. It came in line with the Aleutian trench, under the Pacific, 4,000 fathoms deep. The earthquakes lasted two weeks.

This colossal movement of blocks of the earth’s crust hundreds of miles across gave one the impression that we knew little of what was going on. Remembering that seventy-two percent of the earth’s surface is covered by oceans and that less than ten percent is really inhabited, I awoke to how much there was to learn. If whole forests and their roots could float away into the Pacific currents, with all their plants and animals and seeds and bacteria, what might not have occurred in past ages, when such jostling of crust blocks was common.