Eric Calais (IMAGE) Purdue University Caption Eric Calais, a Purdue associate professor of geophysics, shows equipment he used to track movements of the continent of Asia over a 10-year period. In his right hand, Calais holds an example of the geodetic markers he and his team drilled into the Earth's surface to track movements as small as one millimeter. The data he collected addressed the 40-year debate over how continents respond during collisions of tectonic plates. Credit Purdue News Service photo/David Umberger Usage Restrictions None License Licensed content 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.