The Gulf of California would extend as far north as Indio, were it not for a dam created by the Colorado River. Over three million years, through all of the Pleistocene, the river's delta expanded until it cut off the northern part of the gulf. Since then, the Colorado River has alternated between emptying into the basin, creating a freshwater lake, and emptying into the gulf, leaving the lake to dry and turn to desert. Wave-cut shorelines at various elevations record a repeated cycle of filling and drying over hundreds of thousands of years. The most recent freshwater lake was Lake Cahuilla, also known as the Blake Sea after American professor and geologist William Phipps Blake. It covered over , six times the area of the Salton Sea.