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Geology of the National Parks - Death Valley

 

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Death Valley National Park through time

Precambrian rocks near Badwater
1.8 billion-year-old metamorphic rocks in the Black Mountains above Badwater. Photo by Ray Nordeen, NPS.

Dawn’s Early Light

Middle Precambrian time

The Earth is 4.5 billion years old, but most of the rocks dating from the earlier half of that long history are now concealed beneath thick accumulations of younger deposits. Only in a few places (e.g., Greenland and southern Africa) has deep erosion exposed rocks older than 3 billion years. In the Death Valley region the oldest are about 1.8 billion years, but these have been severely metamorphosed, i.e., altered, re-crystallized, or even partially re-melted by the Earth’s internal heat and by the load of overlying younger rocks. Hence, the record of early times is poorly preserved and the history of the Earth’s dawn almost indecipherable. By comparison, fresher younger rocks usually still resemble the sandstone or limestone forming in modern oceans or the lavas of modern volcanoes, thus telling a fuller story of past events. Careful scrutiny of Death Valley’s oldest rocks, however, indicates that the contorted schists, gneisses, rhyolites, and granites are metamorphosed remnants of an ancient volcanic belt with its flanking deposits of mud and sand-perhaps resembling a modern chain of volcanoes like the Andes or Indonesia.

Here in the southwestern U.S., slow rise of the whole region during the last few million years has provided two ways of exposing the old rocks deep within the pile: (1) the Colorado River, by cutting deeply across part of the uplift, has exposed lower levels of the stony layer-cake we call the Grand Canyon; and (2) where up-arching has stretched the crust too far, it has collapsed into the system of enormous basins like Death Valley, where range-front faults have sliced away much of the overburden, revealing ancient rocks on the valley walls. The sombre grey parts of the Black Mountains front, from Badwater southward past Jubilee Pass, consist largely of these deformed metamorphic rocks, boulders of which are abundant on alluvial fans shed from the steep face. Similar rocks in the Panamint Range (easily visited in Warm Spring, Pleasant, and Surprise Canyons) are the westernmost outcrops of ancient continental crystalline crust in this part of North America.

(Excerpt from Death Valley Geology. Rocks and Faults, Fans and Salts. Wes Hildreth, USGS.)


Move forward in time to the Beginnings of a Pacific Coast (Late Precambrian time)
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