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Page 26
We turn now to deposits from water of these two substances, especially
the first. About the Old Faithful geyser is a mound about one hundred
and forty-five feet broad at the base, twelve feet high, jeweled over
with pools of beauty of every shape, beaded and fretted with glories of
color never seen before except in the sky. How were they made?
Water is a general solvent. It can take into its substance several
similar bulks of other substances without greatly increasing its own,
some actually diminishing it. Hot alkaline water will dissolve even
silica rock. When water is saturated with sugar, salt, or other
substance, if a little or much water is evaporated some of the
saturating substance must be deposited as a solid. All crystals, as
quartz or diamonds, have been made by deposits from water. Hot water
can hold in solution much more of a solid than cold water. Therefore,
when hot water comes out of the earth and is cooled, some of the
saturating substance must be deposited as a solid. It is done in
various ways, especially two.
Suppose a little pool with perpendicular sides, say twenty feet across.
It leaps and boils two feet high. It deposits nothing till the water
comes to the cooling edge. Then it builds up a wall where it
overflows, and wherever it flows it builds. The result is that you
walk up the gentle slopes of a broad flat cone, and find the little
lakelet in a gorgeous setting, perfectly full at every point of the
circumference. If there is but little overflow, the result may be to
deposit all the matter where it first cools, and make a perpendicular
wall around the cup two or ten feet high. If the overflow is too much
to be cooled at once, the deposit may still be made fifty or one
hundred feet from the point of issue. If the overflow is sufficient,
it may be building up every inch of a vast cone at once, every foot
being wet.
[Illustration: The Punch Bowl, Yellowstone Geysers.]
Many minerals are held in solution and are deposited at various stages
of evaporation. Let us suppose the lake to have the bottom sloping
toward the abysmal center; the different minerals will be assorted as
if with a sieve. At the Sunlight Basin the edge is as flaming red as
one ever sees in the sunlit sky. And every color ever seen in a sunset
flames almost as brilliantly in the varying depths. Suppose a low cone
to be flooded only occasionally, as in the case of the Old Faithful
geyser. The cooled water falling from the upper air builds up, under
the terrible drench of the cataract, walls three or four inches high,
making pools of every conceivable shape, a few inches deep, in which
are the most exquisite and varied colors ever seen by mortal eye. You
walk about on these dividing walls and gaze into the beaded and
impearled pools of a hundred shades of different colors, never equaled
except by that perpetual glory of the sunset.
Consider the case of a pool that does not overflow. Just as lakes that
have no outlet must grow more and more salt till some have become solid
salt beds, so must this pool, tossing its hot waves two or three feet
high, evaporate its water and deposit its solids. Where? First,
against the cooler sides of the rock under the water, tending to reduce
the opening to a mere throat. Second, each wavelet tossed in air is
cooled, and deposits on the edge, solid as quartz, a crust that
overhangs the pool and tends to close it over as with hot ice. It may
build thus a mound fifteen feet high with an open throat in the middle.
Thus the pool has constructed an intermittent geyser. If the water
supply continues, it also destroys itself. The throat closes up by its
own deposits. It is a case of geyseral membranous croup.
I exceedingly longed to try vivisection on a geyser, or at least take
one of half a hundred, drain it off, and make a post-mortem
examination. On my very last day I found opportunity. I found a dead
geyser, though not by any means yet cold. It was still so hot that
people had given it an infernal name. I squeezed myself down through
its hot throat, which seemed a veritable open sepulcher, and found a
cave about twenty-five feet deep, twelve feet wide, and about sixty
feet long. It was elliptical in form, the sides coming together at a
sharp angle at the ends, bottom, and top. The way down to the fiery
heart of the earth had simply grown up by deposits of silex on the
sides and at the bottom. The water had evaporated by the intense heat,
and I was in the hot hollow that had once held an earthquake and
volcano. When I squeezed up to the blessed upper air I was glad there
was no help from below.
I could tell of mounds that grew so fast as to inclose the limbs of a
tree, making the firmest kind of a ladder by which I climbed to the
top; of floods that overflowed acres of forest, leaving every tree
firmly planted in solid rock; of mounds hundreds of feet high, covering
twenty acres with forms of indescribable beauty--but I despair. The
half has not been told. It cannot be. Great and marvelous are all Thy
works, Lord God Almighty! In wisdom hast Thou made them all.
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