The Sierra Nevada Mountain Range by:Steven Brazis
The western margin of the continent of North America is built of a succession of
mountain chains folded in broad corrugations, like waves of stone upon whose seaward base beat the mild, small breakers of the Pacific. By far the grandest of all these ranges is the Sierra Nevada, a long and massive uplift lying between the arid deserts of the Great Basin and the Californian exuberance of grain-field and orchard; its eastern slope, a defiant wall of rock plunging abruptly down to the plain; the western, a long, grand sweep, well watered and overgrown with cool, stately forests ; its crest a line of sharp, snowy peaks springing into the sky and catching the alpenglow long after the sun has set for all the rest of America.The Sierras have a structure and a physical character which are individual and unique. The whole Sierra crest was one pile of snow, from whose base crawled out the ice-rivers, wearing their bodies into the rock, sculpturing as they went the forms of valleys, and brightening the surface of their tracks by the friction of stones and sand which were bedded, armor-like, in their under surface. Having made their way down the slope of the Sierra, they met a lowland temperature of sufficient warmth to arrest and waste them. At last, from causes which are too intricate to be discussed at present, they shrank slowly back into the higher summit fastnesses, and there gradually perished, leaving only a crest of snow.
The ice melted, and upon the whole plateau, little by little, a thin layer of soil accumulated, and, replacing the snow, there sprang up a forest of pines, whose shadows fall pleasantly today over rocks which were once torrents of lava and across the burnished pathways of ice. Rivers, pure and sparkling, thread the bottom of these gigantic glacier valleys. The volcanoes are, for the most part, extinct, and the whole theater of this impressive geological drama is now the most glorious and beautiful region of America.
Five distinct periods divide the history of the range. First, the slow gathering of marine sediment within the early ocean during which incalculable ages were consumed. Second, in the early Jurassic period this level sea-floor came suddenly to be lifted into the air and crumpled in folds, through whose yawning fissures and ruptured axes outpoured wide zones of granite. Third, the volcanic age of fire and steam. Fourth, the glacial period, when the Sierras were one broad field of snow, with huge dragons of ice crawling down its slopes, and wearing their armor into the rocks. Fifth, the present condition, a playground for campers, backpackers and climbers.
From latitude 35 to latitude 39 30 the Sierra lifts a continuous chain, the profile culminating in several groups of peaks separated by deeply depressed curves or sharp notches, the summits varying from eight to fifteen thousand feet, seven to twelve thousand being the common range of passes. Near its southern extremity, in San Bernardino County, the range is cleft to the base with magnificent gateways opening through into the desert. From Walker's Pass for two hundred miles northward the sky line is more uniformly elevated; the passes averaging nine thousand feet high, the actual summit a chain of peaks from thirteen to fifteen thousand feet. This serrated snow and granite outline of the Sierra Nevada, projected against the cold, clear blue, is the blade of white teeth which suggested its Spanish name.
Northward still the range gradually sinks; high peaks covered with perpetual snow are rarer and rarer. Its summit rolls on in broken, forest-covered ridges, now and then overlooked by a solitary pile of metamorphic or irruptive rock. At length, in Northern California, where it breaks down in a compressed medley of , ridges, and open, level expanses of plain, the axis is maintained by a line of extinct volcanoes standing above the lowland in isolated positions. The most lofty of these. Mount Shasta, is a cone of lava fourteen thousand four hundred and forty feet high, its broad base girdled with noble forests, which give way at eight thousand feet to a cap of glaciers and snow. Beyond this to the northward the extension of the range is quite difficult to definitely assign, for, geologically speaking, the Sierra Nevada system occupies a broad area in Oregon, consisting of several prominent mountain groups, while in a physical sense the chain ceases with Shasta; the Cascades, which are the apparent topographical continuation, being a tertiary structure formed chiefly of lavas which have been outpoured long subsequent to the main upheaval of the Sierra.
About the author
Steven Brazis has been hiking and climbing in the Sierras since he was a boy (early 1950's). Visit his site: http://www.morerockclimbing.com for information, news and articles on mountaineering and rock climbing. Find him also at: http://www.rockclimbinglife.com , a social networking site for rock climbers.
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