Post by david on Feb 13, 2009 11:42:39 GMT -8
For countless millions of years the molten planet boiled, water existed at first only as a vapor and the nascent crust interminably surrendered to waves of fresh magma from below. Huge masses of red-hot material formed beneath the surface and floated upward only to be subsumed by the boiling miasma. Though still red-hot just under a thin outer layer, Earth cooled a bit after billions of years and just before the crust was set in stone the Sierra Nevada batholith struggled upward from the fiery depths and, exposed now to attacks from above ground, began a new struggle for existence.
Nothing is immune to the ravages of wind, water and gravity; given enough time, even the mightiest mountains will eventually crumble to dust and be swept into the sea. Each year, the alternate freezing and thawing of snow and ice and rock itself makes tiny cracks and crevices imperceptibly larger until, inevitably, chunks of earth and rock break off and are drawn downward by the constant force exerted by that molten mass of matter that still burns in Earth’s core.
But the Rhode Island-sized batholith that now houses the headwaters of the Merced and Tuolumne rivers had to contend with forces far more powerful than seasonal changes in temperature and the vagaries of rain and wind. Millions of years after it bobbed to the surface in the final stages of Earth’s shell cooling, and for millions more years while the atmosphere formed and the impacts of weather began to alter the firmament, new forces joined the fray and transformed what had been a huge, cold puddle of igneous stone into one of the wonders of the world.
First, huge tectonic plates that have always been and will continue for millions more years to be in motion pressed against one another, competing for the same space. The result was a cracking and crumbling of the formerly monolithic mass into a jumbled heap of broken granite thrust upward by the battle between goliaths taking place below.
And then the never-ending process of cooling took a dramatic though temporary turn. Temperatures dipped, coating most of Earth’s surface with ice. A thick blanket of frozen water gave way to gravity’s pull and slowly began moving downhill toward the coast. As its millions of tons of mass inched along, a layer of crumbled stone became a buffer and a lubricant and an abrasive compound that facilitated movement while exacerbating the grinding action. Laced with hard, sharp crystals from the plutonic body of rock being consumed in the process, this rasping layer of animated matter cut through the solid stone like a colossal sheet of sandpaper, first forming and then polishing new surfaces on the floor and along the sides of formerly ‘V’ but now ‘U’ shaped passages.
And so, the Hetch-Hetchy and Yosemite Valleys were sculpted by stone and ice. The former is now largely obscured by a man-made lake, but the latter is a jewel in the crown of protected natural landscapes. The bisection of half-dome and the shearing of El Capitan stand as mute testimony to the power of fire and ice and wind and gravity and, most of all, to the power of time.
Nothing is immune to the ravages of wind, water and gravity; given enough time, even the mightiest mountains will eventually crumble to dust and be swept into the sea. Each year, the alternate freezing and thawing of snow and ice and rock itself makes tiny cracks and crevices imperceptibly larger until, inevitably, chunks of earth and rock break off and are drawn downward by the constant force exerted by that molten mass of matter that still burns in Earth’s core.
But the Rhode Island-sized batholith that now houses the headwaters of the Merced and Tuolumne rivers had to contend with forces far more powerful than seasonal changes in temperature and the vagaries of rain and wind. Millions of years after it bobbed to the surface in the final stages of Earth’s shell cooling, and for millions more years while the atmosphere formed and the impacts of weather began to alter the firmament, new forces joined the fray and transformed what had been a huge, cold puddle of igneous stone into one of the wonders of the world.
First, huge tectonic plates that have always been and will continue for millions more years to be in motion pressed against one another, competing for the same space. The result was a cracking and crumbling of the formerly monolithic mass into a jumbled heap of broken granite thrust upward by the battle between goliaths taking place below.
And then the never-ending process of cooling took a dramatic though temporary turn. Temperatures dipped, coating most of Earth’s surface with ice. A thick blanket of frozen water gave way to gravity’s pull and slowly began moving downhill toward the coast. As its millions of tons of mass inched along, a layer of crumbled stone became a buffer and a lubricant and an abrasive compound that facilitated movement while exacerbating the grinding action. Laced with hard, sharp crystals from the plutonic body of rock being consumed in the process, this rasping layer of animated matter cut through the solid stone like a colossal sheet of sandpaper, first forming and then polishing new surfaces on the floor and along the sides of formerly ‘V’ but now ‘U’ shaped passages.
And so, the Hetch-Hetchy and Yosemite Valleys were sculpted by stone and ice. The former is now largely obscured by a man-made lake, but the latter is a jewel in the crown of protected natural landscapes. The bisection of half-dome and the shearing of El Capitan stand as mute testimony to the power of fire and ice and wind and gravity and, most of all, to the power of time.