Stephen Marshak is Professor of Geology at the University of Illinois, Urbana-Champaign, where he is also the Director of the School of Earth, Society, and Environment. He holds an AB from Cornell University, an MS from the University of Arizona, and a PhD from Columbia University. Steve's research interests lie in structural geology and tectonics. This work has taken him into the field on multiple continents. He has also won his college's and university's highest teaching awards. In addition to research papers and Earth: Portrait of a Planet, Steve has authored Essentials of Geology; and has co-authored Laboratory Manual for Introductory Geology; Earth Structure: An Introduction to… Structural Geology and Tectonics; and Basic Methods of Structural Geology.