THE LESSER LAKES OF THE TAHOE REGION AND HOW THEY WERE FORMED
This is not to be a description of the scores of Glacial Lakes found
in the Tahoe region, but an answer to the questions so often
asked about practically all of these lakes, as to their origin and
continuance.
Rich as our Sierras are in treasures none are more precious than
these. They give one pleasing surprises, often when least expected.
For while the tree-clusters, the mountain-peaks, and the glowing
snow-banks throw themselves into our view by their elevated positions,
the retiring lakes, secluded, modest, hide their beauty from us until
we happen to climb up to, or above, them.
From the higher summits how wonderfully they appear. Let the eye
follow a fruitful branch of an apple, pear or peach. How the leaves,
the stem, the fruit occur, in sure but irregular order. It is just
so with the glacial lakes of the Sierras. They are the fruit of the
streams that flow from the glacial fountains. They lie on rude and
unexpected granite shelves,--as Le Conte Lake; under the shadow of
towering peaks,--as Gilmore Lake; on bald glacier-gouged and polished
tables,--as those of Desolation Valley; embosomed in deep woods,--as
Fallen Leaf, Heather and Cascade; in the rocky recesses of sloping
canyons,--as Susie, Lucile and the Angoras; hidden in secret recesses
of giant granite walls,--as Eagle; or sprawling in the open,--as Loon,
Spider, etc.
What a variety of sizes, shapes and characteristics they present.
There are no two alike, yet they are nearly all one in their
attractive beauty, in the purity of their waters, and in the glory,
majesty, sublimity and beauty mirrored on their placid faces.
In poetic fashion, yet with scientific accuracy, John Muir thus
describes their origin in his _Mountains of California_, a book
every Tahoe lover should possess:
When a mountain lake is born,--when, like a young eye, it
first opens to the light,--it is an irregular, expressionless
crescent, inclosed in banks of rock and ice,--bare, glaciated
rock on the lower side, the rugged snout of a glacier on the
upper. In this condition it remains for many a year, until at
length, toward the end of some auspicious cluster of seasons,
the glacier recedes beyond the upper margin of the basin,
leaving it open from shore to shore for the first time,
thousands of years after its conception beneath the glacier
that excavated its basin. The landscape, cold and bare, is
reflected in its pure depths; the winds ruffle its glassy
surface, and the sun thrills it with throbbing spangles,
while its waves begin to lap and murmur around its leafless
shores,--sun-spangles during the day and reflected stars
at night its only flowers, the winds and the snow its only
visitors. Meanwhile, the glacier continues to recede, and
numerous rills, still younger than the lake itself, bring
down glacier-mud, sand-grains, and pebbles, giving rise to
margin-rings and plats of soil. To these fresh soil-beds come
many a waiting plant. First, a hardy carex with arching
leaves and a spike of brown flowers; then, as the seasons grow
warmer, and the soil-beds deeper and wider, other sedges take
their appointed places, and these are joined by blue gentians,
daisies, dodecatheons, violets, honey-worts, and many a lowly
moss. Shrubs also hasten in time to the new gardens,--kalmia
with its glossy leaves and purple flowers, the arctic willow,
making soft woven carpets, together with the healthy bryanthus
and cassiope, the fairest and dearest of them all. Insects
now enrich the air, frogs pipe cheerily in the shallows, soon
followed by the ouzel, which is the first bird to visit a
glacier lake, as the sedge is the first of plants.
So the young lake grows in beauty, becoming more and more
humanly lovable from century to century. Groves of aspen
spring up, and hardy pines, and the hemlock spruce, until it
is richly overshadowed and embowered. But while its shores
are becoming enriched, the soil-beds creep out with incessant
growth, contracting its area, while the lighter mud-particles
deposited on the bottom cause it to grow shallower, until at
length the last remnant of the lake vanishes,--closed forever
in ripe and natural old age. And now its feeding-stream goes
winding on without halting through the new gardens and groves
that have taken its place.
The length of the life of any lake depends ordinarily upon the
capacity of its basin, as compared with the carrying power of
the streams that flow into it, the character of the rocks over
which these streams flow, and the relative position of the
lake toward other lakes. In a series whose basins lie in the
same canyon, and are fed by one and the same main stream,
the uppermost will, of course, vanish first unless some other
lake-filling agent comes in to modify the result; because at
first it receives nearly all of the sediments that the stream
brings down, only the finest of the mud-particles being
carried through the highest of the series to the next below.
Then the next higher, and the next would be successively
filled, and the lowest would be the last to vanish. But this
simplicity as to duration is broken in upon in various ways,
chiefly through the action of side-streams that enter the
lower lakes direct. For, notwithstanding many of these side
tributaries are quite short, and, during late summer, feeble,
they all become powerful torrents in spring-time when the
snow is melting, and carry not only sand and pine-needles, but
large trunks and bowlders tons in weight, sweeping them down
their steeply inclined channels and into the lake basins with
astounding energy. Many of these side affluents also have
the advantage of access to the main lateral moraines of the
vanished glacier that occupied the canyon, and upon these they
draw for lake-filling material, while the main trunk stream
flows mostly over clean glacier pavements, where but little
moraine matter is ever left for them to carry. Thus a small
rapid stream with abundance of loose transportable material
within its reach may fill up an extensive basin in a few centuries,
while a large perennial trunk stream, flowing over clean,
enduring pavements, though ordinarily a hundred times larger,
may not fill a smaller basin in thousands of years.
[Illustration: Tamarack and Echo Lakes]
[Illustration: Cascade Lake, Near the Automobile Bouldvard, Lake Tahoe]
[Illustration: Memorial Cross at Donner Lake]
Many striking examples of these successive processes may be seen in
the Tahoe region, as, for instance, Squaw Valley, which lies between
the spurs of Squaw Peak and Granite Chief. This was undoubtedly
scooped out by a glacier that came down from Squaw Peak and Granite
Chief. The course of the ice-sheet was down to the Truckee River.
When the glacier began to shrink it left its terminal moraine as a
dam between the basin above and the river below. In due time, as the
glacier finally receded to a mere bank of half-glacierized snow on the
upper portions of the two peaks, the basin filled up with water and
thus formed a lake. Slowly the sand and rocky debris from the peaks
filled up the lake, and in the course of time a break was made in
the moraine, so that the creek flowed over or through it and the lake
ceased to exist, while the meadow came into existence.