Altogether the glacial Tian Shan glaciation occupied an area of c. . The valleys show characteristic effects of Pleistocene glaciation. Sea level changes are mostly due to glaciation or plate tectonics. Iowa can be divided into eight landforms based on glaciation, soils, topography, and river drainage. All Saddle Plateau cones predate the last glaciation. It is associated with the formation of the mammoth steppe and continental glaciation. During the Quaternary glaciation, ice sheets appeared. Eastern South Dakota has many natural lakes, mostly created by periods of glaciation. Nonetheless, there is evidence of Antarctic marine glaciation in the Turonian Age. All three species became extinct before the last glaciation. The last continental glaciation ended ago. Such evidence suggests major periods of glaciation prior to the current Quaternary glaciation. High-latitude regions have since undergone repeated cycles of glaciation and thaw, repeating about every . Natural lakes are generally found in mountainous areas, rift zones, and areas with ongoing glaciation. Climates were warm, with no evidence of glaciation.