The Trona Pinnacles rise from the bottom of an ancient lakebed as one of the most unique geologic landscapes in the California Desert. More than 500 tufa, or calcium carbonate, spires spread across a 14 square mile area of the Searles Lake basin, ranging from small coral-like boulders to formations more than 140 feet tall. They formed between 10,000 and 100,000 years ago when Searles Lake was part of a chain of interconnected lakes flowing from the Owens Valley to Death Valley. During the Pleistocene, this area was once under 640 feet of water. In 1968, the Trona Pinnacles were designated a National Natural Landmark by the U.S. Department of the Interior to preserve one of North America's most outstanding examples of tufa tower formation.