Dating topography of the sierra nevada
Glacial deposits, mainly moraines made up of unconsolidated glacial till, are dated by glaciologists worldwide in order to determine each glaciers response to climate variability as well as the rate of glacial flow [Erickson, 1996].
Today, the study of glaciers is increasingly important.
1; Faulds et al., 2005; Garside et al., 2005; Henry, 2008).
Oligocene ash-flow tuffs erupted from calderas in central Nevada flowed westward down these drainages (Deino, 1985; Faulds et al., 2005).
Today, only 10 percent of the Earth is covered by glaciers compared to an astounding 30 percent during the Pleistocene glaciations, occurring from 1.8 million to 10,000 years B. For the last 1.5 million years, glaciers have covered the Sierra Nevada, carving deep into the landscape forming canyons such as the beautiful Yosemite Valley in Yosemite National Park [Sauchyn, 2003].
Today, glacial evidence is seen primarily in the landforms left behind, many of which may be seen within the United States in the Sierra Nevada mountain range.
If they erupt from volcanoes as lava, they are called extrusive rocks.Here we describe a technique for estimating the age of topographic relief by mapping the low-temperature thermal structure imparted by river incision using the ages of apatites determined from their uranium, thorium and helium contents.The technique exploits horizontal variations in temperature in the shallow crust that result from range-normal river drainages, because cooling beneath ancient river valleys occurs earlier than beneath intervening ridges.Variations in topography through time have profound implications for processes as obvious as erosion and sedimentation and as diverse as global climate and the formation of mineral deposits.The interplay between topography and tectonics is exemplified by the evolution of topography of the Sierra Nevada and Great Basin (United States), and by geologists' interpretation of that evolution.
Search for dating topography of the sierra nevada:
The upward motion of rock masses relative to the Earth's surface has been documented for most of the main mountain belts using thermochronological and petrological techniques.