The Great Basin of western North America stretches from the crest of the Sierra Nevada to the summit of the Wasatch Plateau and from southern Nevada to central Oregon; this vast, high desert covers western Utah, most of Nevada, eastern California, south-central Oregon, the southeastern rim of Idaho and extreme southwestern Wyoming. As its name implies, the rivers and streams of the Basin do not flow to the sea; rather, they empty into shallow, saline lakes that expand and contract with the seasons. The Great Salt Lake, a remnant of Pleistocene Lake Bonneville, is, of course, the largest of these basin lakes.
Cut off from precipitation by high mountains to its east and west, the Great Basin is North America's largest desert; sage grasslands and salt flats cover the majority of its surface with pine and juniper woodlands limited to the higher terrain of its stark ranges. During the Miocene-Pliocene Uplift, which began about 15 million years ago, the crust of the Great Basin began to stretch and numerous north-south fault lines developed; slippage along these faults has produced the linear, wave-like ranges that characterize the landscape. In fact, the Wasatch Front, on the east edge of Salt Lake City, is the easternmost of these fault-block ranges.
Assembled by the fusion of exotic terrains during the Mesozoic Era, the Great Basin has thus been pulling apart for the past 15 million years. With the accelerated rise of the Sierra Batholith, 4 million years ago (a process that continues today), the crust of the Basin continues to stretch and fracture. Eventually, the ocean will invade the Basin, likely opening northward from the Gulf of California.
