A geological layer cake
The Aktau Mountains are a 30-kilometer-long range of sedimentary badlands located in Kazakhstan's Altyn-Emel National Park. Their name translates to "White Mountains," but the landscape is famous for its bright stripes of red, yellow, green, and blue. These colors are not random; they are a record of changing environmental conditions during the Paleogene and Neogene periods, roughly 25 to 30 million years ago. At that time, this arid desert was the floor of a large freshwater lake system.
The distinct colors come from different minerals within the clay and sandstone layers. The bright red and pink strata were formed in a hot, humid climate when iron-rich sediments were exposed to atmospheric oxygen, creating hematite. The white, yellow, and greenish layers indicate periods when the lake bed was submerged in an oxygen-poor, or reducing, environment. The entire sedimentary deposit reaches a thickness of up to 1,200 meters, a massive vertical record of climate history. The soft rock erodes easily, and seasonal rains constantly carve new channels and expose different strata, changing the appearance of the canyons from year to year.
Repository of prehistoric life
The same sediments that paint the hills also preserved a remarkable collection of Cenozoic fossils. The Aktau Mountains are a paleontological site, recording life on the subtropical lake shores millions of years ago. Because the landscape is almost entirely devoid of vegetation, fossils are often exposed directly on the surface.
Excavations have uncovered the remains of ancient crocodiles, giant turtles, and a diverse range of mammals. Among the most significant finds are giant hornless rhinoceroses, including members of the Paraceratherium genus, which were among the largest land mammals to have ever lived. Paleontologists have also found fossils of brontotheres (extinct rhino-like mammals) including a nearly complete skeleton of a new genus, Aktautitan hippopotamopus, named after these mountains. Remains of early mastodons, deer, and predators like Aktaucyon (an early bear-dog) fill out the prehistoric ecosystem. The site also contains well-preserved ancient flora, with imprints of 56 plant species including poplar, willow, and elm.