My experiments with volcanoes

by Thomas Augustus Jaggar

The notion of erosion pulling down hills to a flat plane near sea level is fascinating to geometry-minded people, but not to the mechanically minded. A flat plane near sea level in the Mississippi delta is where the river has swung right and left against valley walls, over its own flood plain. A flat plain, secured by ice sheets or planed off by encroaching wave action as land sinks is mechanically probable. In these circumstances we look for river or ice or wave-beach deposits. But an “almost plane” occasioned by the multiple action called erosion down to base level is to me the delightful dream of map students. If a landscape has been planed off, a machine router or planer did it. The great rivers of China have had a long time to bang back and forth against their confining boxes of rock and on top of their own mud.

To return to geyser-spring experiments, I built a simple quart flask surmounted by a four-foot glass tube. At the top the tube rose through a cork in the bottom of a two-foot pan. In the side of the cork of the flask was a second tube with a hose leading up to a reservoir bottle of water. The reservoir bottle could be raised or lowered. If the water in it was level with the pan, there was hydrostatic equilibrium: the pan a pool, the bottle a source, the flask and tube full. When we applied heat to the bottom of the flask, the water boiled, the pan overflowed, and some cold water from the bottle chilled the flask. The pan had become a boiling spring.

Next we lowered the reservoir bottle. The reduced head of water permitted no overflow at the pan, and steam bubbles accumulated in the four-foot upright tube. The boiling point was controlled by four feet of water pressure. If the bubble lift reduced this to three feet, there was a lower boiling point, the pressure was reduced by overflow above, and the whole flaskful boiled. The geyser tube became a regular geyser at intervals of a minute and a half, with eruptions enduring twenty seconds.

This was a miniature of Old Faithful in the Yellowstone. Old Faithful is bigger, its intervals average sixty-five minutes, and they range from thirty-one to eighty-one minutes. It jets up 150 feet for a period of four minutes. It throws out 3,000 barrels of water at each eruption. Our little machine threw up about a pint to a height of four feet.

We hear much about soaping geysers as an artificial stimulus. The apparatus in our laboratory showed the effect of soap right away. When some soap was put in the pan, the intervals of a minute and a half shortened to one minute. Soapsuds accumulated in the tube and depressed the water to the neck of the flask. The multiple bubbles, film against film, made the water system viscous. The myriads of tiny steam bubbles formed so fast that they shortened the lifting time for the column. If the height of the reservoir bottle was so adjusted that the geyser didn’t quite know whether it was a geyser or a boiling spring, the soap made the decision, and the thing went off with a bang.

This simple group of experiments makes springs very real. The Yellowstone explosive springs differ from other springs in having superheated steam from live lavas to heat them. The rock is cracked and the water is doing a job of solution and deposition. It deposits stout tough silica around some openings and builds them up against the head of groundwater, and they become geysers. It deposits lime dissolved off underlying limestone at Mammoth, and this makes sculptured terraces but not explosive springs because the temperatures are not so hot. In both lime and silica regions, blue-green algae, which love hot water, decoratively sculpture the pools.

Like a magician I exhibited the artificial geysers before New York and Boston science academies, and gave the summaries of the results of our geyser experiments, as follows: (1) Boiling springs are like other springs, controlled by the head or pressure of underground water in the hills. (2) Upstreaming of heated water and building up of silica (convection is the scientific jargon) may push the vent of a boiling spring even higher than its source (reversed head). (3) In this delicate condition, even rainfall or sinter building up or outburst at a lower level or clogging of a pipe may change spring to geyser or geyser to spring. There are many more boiling springs than there are geysers, and many more hot springs than there are boiling springs, and the word cold means nothing at all. There may be boiling springs under New York City if you go deep enough. That is why the riot of geyser apparatus is worth thinking about. (4) Irregular geysers overflow continually, regular geysers discharge their waters only during eruptions. Both are methods of feeding rivers, just like any other springs. But there is a lot of volcanic heat underground.

This brings up the question of how much a volcanic eruption is like a geyser. Geologists apply a glib word, phreatic, to Japan’s Bandai Volcano, which blew steam and rocks out of the side of a mountain and dammed a river. Hawaiian volcanoes squirt liquid basalt up a crack with flames and red fume and sulfur gas, and almost no steam at all. The answer seems to be that the Palisades of the Hudson may once have been Hawaiian lava eruptions and, further, that lava is still erupting there if you go down deep enough. New York doesn’t know about it, but it sensed it in 1886, when it felt the Charleston earthquake.

All that Catskill water supply of the great city is in cracks above the level of the deep lava, and extends out under Long Island Sound. If the Hudson fault fissure wiggled a little more than usual, and if the deep lava lowered and pulled down some of the Atlantic water, an eruption like Bandai is not impossible in the Watchung Ridge of New Jersey. This is not likely; but the globe has been through revolutions and cataclysms, and the Watchung explosions might start a new geyser basin. Something like that happened in northwest Wyoming in the Pliocene age, during 11 million years, next preceding the ice ages that began 2 million years ago. And the Yellowstone was the result. We shall see more volcano geysers.

Next, the making of deltas became a hobby in our laboratory, in connection with the old leaf deltas scattered on the New England landscape, partly covered with trees within the grounds of the country villas about Boston.