Golden Theories and Glaciers.
The many inquiries that the author has received concerning his views
upon the gold deposits of California, has induced him to add this
chapter to his work.
It has been said by an earnest and astute observer, that “The cooled
earth permits us no longer to comprehend the phenomena of the primitive
creation, because the fire which pervaded it is extinguished,” and
again that “There is no great foundation (of truth), which does not
repose upon a legend.” There has been a tradition among the California
Indians, that the Golden Gate was opened by an earthquake, and that
the waters that once covered the great plain of the Sacramento and San
Joaquin basins were thus emptied into the ocean. This legendary geology
of the Indians is about as good and instructive as some that has been
taught by professors of the science, and as scarcely any two professors
of geology agree in their theories of the origin and distribution
of the gold in California, I have thought it probable that a few
_unscientific_ views upon the subject will interest my readers.
The origin of the gold found in California seems to me to have been
clearly volcanic. The varying conditions under which it is found may
be accounted for by the varying heat and force of the upheaval, the
different qualities of the matrix or quartz that carried the gold
and filled the fissures of the veins or lodes, the influence that
resistance of the inclosing walls may have exerted when it was slight
or very great, and finally the disintegrating influences of air, water,
frost and attrition of the glaciers, and the deposition in water.
The theories of aqueous deposit (in the lodes) and of electrical
action, do not satisfy my understanding, and I go back in thought to
the ten years of observation and practical experience in the gold
mines, and to the problems that were then but partially solved. Looking
at California as it is to-day, it will be conceded that its territory
has been subjected to distinct geological periods, and those periods
greatly varying in their force in different parts of the State. Within
the principal gold-bearing region of California, and especially along
the line of or near the Carson vein or lode, coarse gold has been
found, and in such large masses, free of quartz, as to force the
conviction upon the mind that the gold so found had been thrown out
_through_ and _beyond_ its matrix into a bed of volcanic ashes, very
nearly assuming the appearance that lead might assume when melted
and thrown in bulk upon an ash heap. Where the resistance was great,
as when thrown through wall rocks of gneiss, or green stone, the
liquefaction of the quartz seems to have been more complete, and the
specific gravity of the gold being so much greater than that of the
quartz, its momentum, when in large quantities, carried it out beyond
its matrix, leaving the more diffused particles to be held suspended in
the fast cooling quartz, or to settle into “pockets,” or small fissures.
Prof. Le Conte says: “The invariable association of metaliferous veins
with metamorphism demonstrates the agency of heat.” Experiments of
Daubre and others prove that water at 750° Fahr. reduces to a pasty
condition nearly all rocks. Deposits of silica in a gelatinous form,
that hardens on cooling, may be seen at some of the geysers of the
Yellowstone; the heat, no doubt, being at a great depth. Quartz, like
glass and lava, cools rapidly _externally_ when exposed to air, or
a cool surface, and would very readily hold suspended any substance
_volatilized_, or crudely mixed into its substance. Its difficult
_secondary_ fusion is no obstacle to a belief in the capacity of heat
under great pressure, to account for the phenomena that may be observed
in the gold mines. Ashes derived from lavas have been found rich in
crystalline substances. Crystals and microliths, and pyrites in cubes
are, no doubt, of volcanic origin. The eruptions of moderate character
seem to be the result of igneous fusion, while those of an explosive
type are probably aquæ-igneous.
It is altogether probable from experiments tried by Stanislas Muenier
and others, that the sudden removal of pressure is a sufficient cause
of superheated water and mineral substances flashing into steam and
lava. The geysers are evidently formed by varying temperature and
interruption of flow by removal of pressure. Mr. Fanques, in an article
in the _Popular Science Monthly_ for August, 1880, says: “Discovery of
microliths enclosed in volcanic rocks is a proof of immediate formation
of crystals.”
The phenomena attending the recent eruptions in Java demonstrate the
incredible force and chemical effects of superheated steam. Modern
researches and experiments in mechanical and chemical forces have
greatly modified the views once entertained by geologists, and I think
that it will now be conceded that repeated volcanic disturbances,
taken in connection with the action of glaciers, will account for
most, if not all, the phenomena discoverable in the gold fields and
mountains of California. As a rule, gold-bearing veins in clay or
talcose slates have the gold more evenly diffused than those found in
the harder rocks, where pockets of crystals, pyrites and gold will
most likely be found. If gold is found in seams or masses it will be
very free from impurities, and the quartz itself will be most likely
white and vitreous. When gold is found in or near to a lode that has
been decomposed, it will be found porous and ragged, but if it has
been deposited some distance from its source it will be more or less
rounded and swedged by contact with the stones and gravel that were
carried with it by the stream of water or ice that conveyed it to its
placer. In the beds of the ancient and more modern rivers the gold
is much more worn than that found in the ravines or gulches, and the
coarser gold will be found at the bottom, the scale gold in the gravel
above, and the fine or flour gold in the mixture of clay, gravel and
sand nearer the surface. The scale gold, no doubt, has been beaten by
repeated blows of stones brought in contact with it while moving in the
bed of the stream, and the flour gold is that reduced by the continual
attrition of the moving mass upon the gold.
Prof. Le Conte says: “There are in many parts of California two systems
of river beds--an old and a new.... The old, or dead, river system runs
across the present drainage system in a direction far more southerly;
this is especially true of northern members of the system. Farther
south the two systems are more nearly parallel, showing less movement
in that region. These old river beds are filled with drift gravel, and
often covered with lava.” The lava referred to is relatively of modern
origin, and the molten streams have in many instances covered the
ancient streams, and in others cut them in twain. The “Blue Lead” is a
very old river bed that has been the principal source of supply of the
placer gold of the northern mines, and it must have existed as a river
long anterior to the more modern upheavals that disturbed its course
by forming mountain torrents to rend its barriers and cut across its
channel. That channel crosses some of the present tributaries of the
Sacramento and San Joaquin and contains fossil remains of trees, plants
and fruits not now indigenous to California.
The well rounded boulders and pebbles found in the beds of these
ancient rivers render it probable that they were of considerable
length, and that they may have been the channels of very ancient
glaciers. It is also probable that the region covered by glaciers
at different epochs is much more extensive than has been generally
supposed. To me it appears probable, that during some of the eras of
formation, they may have stretched across the entire continent. I have
not space to give in detail the evidences of glacial action, but will
simply state that _remains_ of glaciers may be seen by an observing
eye at intervals from the Atlantic to the Pacific; in Minnesota and
in the Rocky Mountains, they are especially abundant. Prof. Le Conte
says: “The region now occupied by the Sierra range was a marginal sea
bottom, receiving abundant sediments from a continent to the east.
At the end of the Jurassic, this line of enormously thick off-shore
deposits yielded to horizontal thrust, was crushed together and swollen
up into the Sierra range. All the ridges, peaks and canyons, all that
constitutes the grand scenery of these mountains are the result of an
almost inconceivable subsequent erosion.”
I have no doubt of the truth of this theory of formation as it relates
to the Sierra Nevada ranges as they exist to-day, for the intrusion
of the granite into the slate formations suggests a force far greater
than can be ascribed to volcanic action alone. The _previous_ condition
of the “continental mass” can not be so well imagined; yet reasoning
from what we know of the present condition of the Sierras we may with
propriety assume that great changes had occurred in the territory
embracing the Sierras Nevada long prior to their upheaval. The changes
that have occurred since are too abundant and enduring to require more
than a reference to the localities. The “glacier pavements” of the
Sierras are so conspicuous that, as Mr. John Muir says: “Even dogs and
horses gaze wonderingly at the strange brightness of the ground, and
smell it, and place their feet cautiously upon it, as if afraid of
falling or sinking.” These glacier-smoothed rocks “are simply flat or
gently undulating areas of solid granite which present the unchanged
surface upon which the ancient glaciers flowed, and are found in the
most perfect condition in the sub-alpine region, at an elevation of
from 8,000 to 9,000 feet. Some are miles in extent, only interrupted
by spots that have given way to the weather, while the best preserved
portions are bright and stainless as the sky, reflecting the sunbeams
like glass, and shining as if polished every day, notwithstanding they
have been exposed to corroding rains, dew, frost and snow for thousands
of years.”
This statement of Mr. Muir will especially apply to the “glistening
rocks” at the sources of the Merced and Tuolumne rivers, in view on
this trail through the Mono Pass. The evidences of past glacial action
in polishing the domes, mountains and valleys _above_ the Yosemite
valley, are too undeniable for controversy, but how much of the
Yosemite itself may have been produced by glacial action will probably
always remain a theme for discussion among geologists.
Prof. Samuel Kneeland, the well known author of “Wonders of the
Yosemite,” in a letter to me upon the subject, says: “I think there
can be no doubt that the valley was filled, and 1,000 feet above, by
ice--that while the _mass above_, moved, that in the valley, conforming
to its configuration, was comparatively stationary, lasting much
longer than the first, gradually melting to a lake, now represented by
the Merced river.
“I agree with Prof. Whitney that the valley was the result of a
subsidence, long anterior to the glacial epoch, and that the valley
itself, except upon its edges and upper sides, has not been materially
modified by the glacier movement.” Prof. J. D. Whitney, in his
geological report says: “The Yosemite valley is a unique and wonderful
locality; it is an exceptional creation; ... cliffs absolutely
vertical, like the upper portions of the Half Dome and El Capitan, and
of such immense height as these, are, so far as we know, to be seen
nowhere else.... How has this unique valley been formed, and what are
the geological causes which have produced its wonderful cliffs, and all
the other features which combine to make this locality so remarkable?
These questions we will endeavor to answer, as well as our ability
to pry into what went on in the deep-seated regions of the earth in
former geological ages will permit.” Mr. Whitney explicitly states his
belief that most of the great canyons and valleys have resulted from
aqueous denudation and erosion and cites the cutting through the lava
of Table Mountain at Abbey’s Ferry on the Stanislaus river as proof,
and, continuing, to the exception, says: “It is sufficient to look for
a moment at the vertical faces of El Capitan and the Bridal Veil Rock
turned down the valley, or away from the direction in which the eroding
forces must have acted, to be able to say that aqueous erosion could
not have been the agent employed to do any such work.... Much less can
it be supposed that the peculiar form of the Yosemite is due to the
erosive action of ice.... Besides, there is no reason to suppose, or
at least no proof, that glaciers have ever occupied the valley, or any
portion of it.... So that this theory, based on entire ignorance of the
whole subject, may be dropped without wasting any more time upon it.
“The theory of erosion not being admissible to account for the
formation of the Yosemite valley, we have to fall back on some one
of those movements of the earth’s crust to which the primal forms
of mountain valleys are due. The forces which have acted to produce
valleys are complex in their nature, and it is not easy to classify
the forms, which have resulted from them, in a satisfactory manner.”
After describing the generally received theories of mountain and valley
formations, Mr. Whitney says: “We conceive that, during the process
of upheaval of the Sierra, or possibly at some time after that had
taken place, there was at the Yosemite a subsidence of a limited area,
marked by lines of ‘fault’ or fissure crossing each other somewhat
nearly at right angles. In other and more simple language, the bottom
of the valley sank down to an unknown depth, owing to its support being
withdrawn from underneath, during some of those convulsive movements
which must have attended the upheaval of so extensive and elevated a
chain, no matter how slow we may imagine the process to have been.
Subsidence over extensive areas of portions of the earth’s crust is not
at all a new idea in geology, and there is nothing in this peculiar
application of it which need excite surprise. It is the great amount
of vertical displacement for the small area implicated which makes
this a peculiar case; but it would not be easy to give any good reason
why such an exceptionable result should not be brought about amid the
complicated play of forces which the elevation of a great mountain
chain must set in motion. By the adoption of the subsidence theory for
the formation of the Yosemite, we are able to get over one difficulty
which appears insurmountable to any other. This is the very small
amount of debris at the base of the cliffs, and, even at a few points,
its entire absence.” In the space allotted to this chapter, I am able
only to quote a few passages from Prof. Whitney, but refer the curious
to his recent work, “Climatic Changes of Later Geological Times.”
In contrast to the conclusions arrived at by Prof. Whitney, I extract
from Prof. Le Conte’s Elements of Geology, pages 526 and 527, the
following: “1st. During the epoch spoken of (the glacial) a great
glacier, receiving its tributaries from Mount Hoffman, Cathedral Peaks,
Mount Lyell and Mount Clark groups, filled Yosemite valley, and passed
down Merced canyon. The evidences are clear everywhere, but especially
in the upper valleys, where the ice action lingered longest. 2nd.
At the same time tributaries from Mount Dana, Mono Pass, and Mount
Lyell met at the Tuolumne meadows to form an immense glacier which,
overflowing its bounds a little below Soda springs, sent a branch down
the Ten-ie-ya canyon to join the Yosemite glacier, while the main
current flowed down the Tuolumne canyon and through the Hetch-Hetchy
valley. Knobs of granite 500 to 800 feet high, standing in its pathway,
were enveloped and swept over, and are now left round and polished
and scored in the most perfect manner. This glacier was at least 40
miles long and 1,000 feet thick, for its stranded lateral-moraines may
be traced so high along the slopes of the bounding mountains.” In an
article by John Muir, published in the New York _Tribune_, and kindly
furnished me by Prof. Kneeland, will be seen views differing from those
of Prof. Whitney, but Mr. Muir has spent long years of study upon the
glacial summits of the Sierras, and if an enthusiast, is certainly a
close student of nature. The paper was written to his friend Prof.
Kunkle, of Boston, who had views similar to his own. Mr. Muir says:
“I have been over my glacial territory, and am surprised to find it
so small and fragmentary. The work of ancient ice which you and I
explored, and which we were going to christen ‘Glacial System of the
Merced’ is only a few tiny topmost branches of one tree, in a vast
glacial forest.
“All of the magnificent mountain truths that we read together last
Autumn are only beginning sentences in the grand Sierra Nevada volume.
The Merced ice basin was bounded by the summits of the main range and
by the spurs which once reached to the summits, viz.: the Hoffman
and Obelisk ranges. In this basin not one island existed; all of its
highest peaks were washed and overflowed by the ice--Starr King, South
Dome and all. Vast ice currents broke over into the Merced basin, and
most of the Tuolumne ice had to cross the great Tuolumne canyon.
“It is only the vastness of the glacial pathways of this region that
prevents their being seen and comprehended at once. A scholar might
be puzzled with the English alphabet if it was written large enough,
and, if each letter was made up of many smaller ones. The beds of those
vast ice rivers are veiled with forests and a network of tiny water
channels. You will see by the above sketch that Yosemite was completely
overwhelmed with glaciers, and they did not come squeezing, groping
down to the main valley by the narrow, angular, tortuous canyons of
the Ten-ie-ya, Nevada or South canyons, but they flowed grandly and
directly above all of its highest domes, like a steady wind, while
their lower currents went mazing and swedging down in the crooking and
dome-blocked channels of canyons.
“Glaciers have made every mountain form of this whole region; even the
summit mountains are only fragments of their pre-glacial selves.
“Every summit wherein are laid the wombs of glaciers is steeper on
its north than its south side, because of the depth and duration
of sheltered glaciers, above those exposed to the sun, and this
steepness between the north and south sides of summits is greater in
the lower summits, as those of the Obelisk group. This tells us a
word of glacial climate. Such mountains as Starr Ring, Cloud’s Rest,
and Cathedral Peak do not come under this general law because their
contours were determined by the ice which flowed about and above them,
but even among these inter-basin heights we frequently find marked
difference of steepness between their north and south sides, because
many of the higher of these mountains and crests extending east and
west, continued to shelter and nourish fragmentary glacierets long
after the death of the main trunk to which they belonged.
“In ascending any of the principal streams of this region, lakes in
all stages of decay are found in great abundance, gradually becoming
younger until we reach the almost countless gems of the summits
with basins bright as their crystal waters. Upon the Nevada and its
branches, there are not fewer than a hundred of these lakes, from a
mile to a hundred yards in diameter, with countless glistening pondlets
about the size of moons. Both the Yosemite and the Hetch-Hetchy valleys
are lake basins filled with sand and the matter of morains easily and
rapidly supplied by their swift descending rivers from upper morains.
The mountains above Yosemite have scarce been touched by any other
denudation but that of ice. Perhaps all of the post glacial denudation
of every kind would not average an inch in depth for the whole region.
“I am surprised to find that water has had so little to do with the
mountain structure of this region. None of the upper Merced streams
give record of floods greater than those of to-day. The small water
channel, with perpendicular walls, is about two feet in depth a few
miles above the Little Yosemite. The Nevada here, even in flood, never
was more than four or five feet in depth. Glacial striæ and glacial
drift, undisturbed on banks of streams but little above the present
line of high water mark, is sufficient proof.”
The views entertained by Mr. Muir are, for the most part, in consonance
with my own. That the valley was originally formed as supposed by
Prof. Whitney I do not doubt, but to suppose that the vast bodies
of ice, stated by Mr. Whitney to have existed at the sources of
the Merced river, could have halted in their glacial flow down the
steep declivities of its canyons, seems as absurd as to suppose one
entertaining opposite views “ignorant of the whole subject.” As a
matter susceptible of eternal proof, I will state that in the canyon
below the Yosemite there are existing to-day, large, well rounded
bowlders that I think a geologist would say had been brought from above
the valley; and if so, water alone could scarcely have brought them
over the sunken bed of the valley, or if filled to its present level
of about thirty-five feet descent to the mile, the laws that govern
aqueous deposits would have left those huge masses of rock far above
their present location in the canyon. Some of the bowlders referred
to will weigh twenty tons or more, and, in connection with flat or
partially rounded rocks fallen, probably, from the adjacent cliff, form
waterfalls in the middle of the canyon, of from fifty to one hundred
feet of perpendicular height. The fall through the canyon averages over
two hundred feet to the mile. Well rounded bowlders of granite and
other hard stones may be seen for long distances below the Yosemite,
on hillsides and flats far above the present bed of the river, and, in
some instances, deposited with those bowlders, have been found well
rounded and swedged masses of gold. The experiments and observations
of Agassiz, Forbes and others, render it probable that the valley of
the Yosemite was filled with ice, but that the upper surface moved more
rapidly, carrying down most of the material brought from mountains
above the valley. The observations of Prof. Tyndall render it almost
certain that a glacier does not move as a rigid mass or on its bed, but
as a plastic substance, as asphalt for instance.
Partial liquefaction by pressure would enable a glacier in the Yosemite
to conform to the inequalities of its configuration, and regelation
would perhaps retard its flow sufficiently to enable the more rapid
moving surface and center of the glacier to carry its burden on from
above without marking the lower portion of the inclosing walls, as
for instance, may be seen at Glacier Point. It has been suggested
that “the immense weight of ice that once filled the Yosemite had
an important part in the formation of it.” This idea is untenable,
because the valley must have already been formed, in order for space to
have existed for “the immense weight of ice;” and unless the earth’s
crust under the valley was previously broken as suggested in the able
theory of Prof. Whitney, no possible weight of any kind could exert a
depressing influence upon the surface.
If it were possible, for the reconciliation of geologists, to believe
that the subsidence in the valley occurred at about the close of
the glacial flow, thereby changing the appearance of the inclosing
walls, yet still leaving material to fill the chasm, a great part of
the mystery that will always remain as one of the “Wonders of the
Yosemite,” would then disappear. As it is, we are compelled to believe,
not in miracles, but that the glacier that flowed over the Yosemite was
so great in depth as to leave, like some deep sea or ocean, its bottom
undisturbed by the tumultuous aerial strife upon its surface.
Now, those glacial heights have, at times, a solitude unutterly
profound! Not a bird or beast to break the stillness, nor disturb the
solemn charm. Nor does the Indian, even, loiter on his way, but hastens
on down to his mountain meadows or wooded valleys. There, if anywhere,
the poet’s idea can be realized, that:
“Silence is the heart of all things; sound the fluttering of its
pulse,
Which the fever and the spasm of the universe convulse.
Every sound that breaks the silence only makes it more profound,
Like a crash of deafening thunder in the sweet, blue stillness
drowned
Let thy soul walk softly in thee, as a saint in heaven unshod,
For to be alone with silence, is to be alone with God.”
[Illustration: BIG TREE
(Height, 325 feet; circumference, 100 feet.)]