It consists of a low-seismic velocity anomaly in the mantle which underpins the highest sector of the Rocky Mountains.
This region underwent significant uplift during the Cenozoic[3] starting from 10-5 million years ago and was subsequently eroded by the Colorado River.
[9] Hot springs and geysers above the anomaly are a major source of carbon dioxide and other gases, some linked to chemolithotrophic bacterial communities.
[4] Cenozoic volcanism is also associated with the anomaly,[10] such as potentially the Twin Lakes pluton close to Leadville, Colorado.
[2] Other structures that may be related to the Aspen anomaly are the Lester Mountain zone, the Colorado mineral belt and the Rio Grande Rift.