Motivation: Three independent North American-scale surface wave images find that the mantle beneath the Colorado Rocky Mountains has a velocity < 4.2 km/s, consistent with an asthenospheric temperature that is at or near the dry solidus of peridotite. At a finer scale, body wave tomographic images find that the region is underlain by an enigmatic low velocity mantle that we refer to as the Aspen Anomaly. This project will provide near 3-D teleseismic images of the geometry of the mantle anomaly in central Colorado and will investigate time-space correlation between Cenozoic rock uplift and denudation patterns, magmatism, and the modern day mantle anomaly using a host of integrated geological and geophysical techniques. We seek to understand when and why changes in lithospheric buoyancy occurred in the Rockies, and how these changes have been expressed in terms of Cenozoic magmatism, and the topographic evolution of the highest elevation region of the Rocky Mountains.