Computer Simulation Spanning 2.5 Billion Years of Earth History (video) University of Calgary Share Print E-Mail Loading video... Caption This computer simulation spanning 2.5 billion years of Earth history is showing density difference of the mantle, compared to an oceanic reference, starting from a cooler initial state. Density is controlled by mantle composition as well as slowly cooling temperature; a keel of low-density material extending to about 260 km depth on the left side (x < 600 km) provides buoyancy that prevents continents from being subducted ('recycled' into the deep Earth). Graph on the top shows a computed elevation model. Credit David Eaton, University of Calgary. Usage Restrictions None Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.