Thursday, April 17, 2014
One of the World's Most Precious Places, Under the Volcano
Big glaciers carve deeper valleys than little glaciers. When the massive Merced River glacier joined the Tenaya Creek glacier (with its spillover of additional ice from the Tuolumne Meadows icecap), the combined force of the two ice rivers produced the deep trough of the main valley, 3,000 feet deep (even deeper if the sediments filling the valley floor are removed). The tributary glaciers in Yosemite and Bridalveil Creeks were much smaller and couldn't cut nearly as deep. Their valley floors were left hanging high above the main valley, and today high waterfalls spill over the edges. Bridalveil Fall (in the pictures above and below) is 620 feet high, nearly four times the height of Niagara Falls, but it's one of the smaller waterfalls in Yosemite Valley.
The dark cleft used to be the path of Yosemite Creek! The falls used to be an inconsequential side canyon but the glacier coming south from the high country pushed up a moraine, a pile of glacial debris, and blocked the normal channel of the canyon. The stream's new pathway took it over the brink of the cliff.
under the volcano" in the title because when you stand in the bottom of Yosemite Valley, you are within the frozen magma chambers of a series of volcanoes that once existed here, just five miles or so above. There are eight or nine individual intrusions that make up the valley walls and different susceptibility to erosion has caused the formation of a series of reentrants and coves along with the bold battlements of cliffs like the Cathedral Rocks or El Capitan. Many glacial valleys have long monotonous walls that aren't nearly as appealing a place as Yosemite.
Yosemite is indeed one of the world's most precious places, and I am forever appreciative of living nearby, and being able to share it with you. Enjoy!