Such lakes were important to indigenous Americans. For example, Death Valley contained Lake Manly, some 80 miles long and 600 feet (180 meters) deep. Basins thus held much more water than they do today. During the waning stages of the latest ice age, between 20,000 and 10,000 years ago, the Basin and Range Province was much cooler and wetter than it is today. Similarly, the Mojave Desert of Southern California is so hot and dry that water evaporates before it can accumulate in Death Valley, the lowest point in North America (272 feet below sea level -83 meters). But what if there is not enough water available to fill a rift valley? The lowest point on Earth, the Dead Sea, is in a rift valley in the very dry Middle East. The Basin and Range Province has the world’s 8th deepest lake, Lake Tahoe on the California/Nevada border (1,645 feet 501 meters). These include the world’s deepest, Lake Baikal in Siberia (5,387 feet 1,642 meters deep) and the 2nd and 4th deepest, Lake Tanganyika (4,323 feet 1,318 meters) and Lake Malawi (2,316 feet 706 meters), in the East African Rift. Thus a second characteristic of continental rifts is that their valleys contain most of the deepest lakes in the world. But sometimes the valley floors move downward much faster than these layers can fill them. Layers of sand, mud and gravel deposited by rivers and lakes, along with lava flows and other volcanic materials, fill rift valleys as they form. But in the southern part of the province, where rifting is more advanced, elevations are generally lower-much of the floor of Death Valley in eastern California is below sea level! For example, the floor of a basin in Wyoming, Jackson Hole, is 6,000 feet (1,830 meters) above sea level, while the adjacent Teton Range rises to over 13,000 feet (4,000 meters). There the whole landscape is moving upward, with the ranges rising a little faster than the adjacent basins. First, much of the region-particularly the northern portion-is well above sea level. Lillie, Wells Creek Publishers, 92 pp., 2015, The topography of the Basin and Range Province and Rio Grande Rift reveals the full range of characteristics of a continental rift zone. Modified from “Beauty from the Beast: Plate Tectonics and the Landscapes of the Pacific Northwest,” by Robert J. Earthquakes (white stars) occur when the fault lines separating the basins and ranges suddenly let go. National Park Service sites in continental rift zones reveal long mountain ranges separated by deep valleys (basins) that are partially filled with sedimentary and volcanic material. Earthquakes, fault-block mountains, and volcanism at Guadalupe Mountains National Park and Bandelier and White Sands national monuments are consequences of the ongoing continental rifting.īasin
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