The Basin and Range is best known for being on the move. The B&R region is widening extensively as the ancient Nevadaplano/Mogollon Highland (the Andes-like mountain range in eastern California and Nevada) that collapsed starting 30 million years ago. It was further stretched by the northwestward motion of the San Andreas Fault. This stretching has resulting in a doubling of the surface distance from the state line of Arizona and Nevada out to the California coast in only 17 million years. See this animation to visualize crustal extension. The mountain ranges of Nevada and the rest of the Basin and Range are actually just massive slumped and tilted crustal blocks from extension. The base of the blocks slid down into the lithosphere toward the west. This tilted the tops of most slumping blocks 20-60 degrees, while some like the Virgin Mountains have been tilted almost 90 degrees from their original orientation. Other famous tilted blocks are Mt. Charleston west of Las Vegas, Wheeler Peak at Great Basin National Park, and Mt. Lemmon and Kitt Peak in southern Arizona. Some of these upended blocks expose very ancient crustal rocks that had been part of offshore island arcs accreted to North America. For instance, uplifted and exposed rock layers in the Virgin Mountains are up to 1.7 billion years old. As time has passed, erosion has filled the deep V-shaped valleys between the peaks, creating flat valley floors with shallow lakes called playas. The Bonneville Salt Flats is part of the largest of these playas. Hidden deep beneath the salt flats is a deep valley thousands of feet below but filled with sediments and salt. This crustal extension is even visible in the Grand Canyon. Most of the north-south side canyons are fractures caused by extension. Water, ice, and wind have eroded open these cracks into giant side canyons in the Grand Canyon. A Continent Stretches Out: How Basin and Range Crustal Extension Set the Stage for Parashant Volcanism. Earth's crust may seem thick to humans, but in fact it is extremely thin relative to the thickness of earth's mantle and core. From the surface to the center of the earth is just shy of 4,000 miles. The crust here is 18 miles thick. Basically the crust is less than one percent of the diameter of earth, comparable to the shell of an egg. Meanwhile, the putty-like mantle is fully 84% of Earth's total volume. The mantle is the egg white, and the core is the yolk. Because Earth's crust is brittle, it is full of fractures, also known as faults. These are places where pieces of crust move against each other to relieve tension that builds up by mantle forces that push or pull on them. This has created a patchwork of giant plates that constantly jostle against each other as convecting rock circulates in the mantle.