The Great Basin encompasses
most of the present state of Nevada, the eastern half of Utah and portions of
southern California. South central and eastern Oregon and southern Idaho are
located on the northern boundary. The Great Basin area is an area where
precipitation has no outlet to the ocean.
Lake Bonneville, existed around 14,500 years ago and covered more than 20,000
square miles in Utah and parts of Idaho and Nevada. The water level of Lake
Bonneville maintained a fairly constant level for hundreds of years until the
water level in a singular event dropped approximately 400 feet when part of Red
Rock Pass, which was holding back the water, eroded. The ensuing floodwaters
flowed down the Snake River and joined the Columbia River near the Tri-Cities.
For a short period of time, the resulting floodwaters from Lake Bonneville
increased the size of the Snake River and the Columbia River by more than 20
times their normal flow. After the flood occurred, the water levels of the Great
Salt Lake eventually subsided close to where they are today. The area once
occupied by the lake and other similar bodies of water is now known as the Great
Basin. Petroglyphs in the Great
Basin styles are found on the basalt rims surrounding many of the pluvial lakes,
drainage areas and passageways between different geological altitudes in the
area. A few pictographs are also present.