Mountain ranges are constantly subjected to
erosional forces which work to tear them down. The
basins adjacent to an eroding mountain range are then filled with sediments that are buried and turned into
sedimentary rock. Erosion is at work while the mountains are being uplifted until the mountains are reduced to low hills and plains. The early
Cenozoic uplift of the
Rocky Mountains of Colorado provides an example. As the uplift was occurring some of mostly
Mesozoic sedimentary
strata were removed by erosion over the core of the mountain range and spread as sand and clays across the
Great Plains to the east. This mass of rock was removed as the range was actively undergoing uplift. The removal of such a mass from the core of the range most likely caused further uplift as the region adjusted
isostatically in response to the removed weight. Rivers are traditionally believed to be the principal cause of mountain range erosion, by cutting into bedrock and transporting sediment. Computer simulation has shown that as mountain belts change from tectonically active to inactive, the rate of erosion drops because there are fewer abrasive particles in the water and fewer landslides. ==Extraterrestrial "Montes"==