More than 500 tufa spires (porous rock formed as a deposit from springs of streams), some as high as 140 feet (43 m), rise from the bed of the Searles Lake (dry) basin. Composed primarily of calcium carbonate (tufa), known as tufa pinnacles, formed underwater 10,000 to 100,000 years ago, now exist 2,000 feet above sea level in the Western Mojave Desert. Pinnacles are located within 3,800 acres (15 km2) of federal land managed by the Bureau of Land Management; are inside a BLM Area of Critical Environmental Concern (ACEC) designated to protect and preserve unique resources. Trona Pinnalces National Natural Landmark (Est. 1968), California Desert National Conservation Area.