I was born in Berea, Kentucky and graduated from Berea College with a degree in Geology. I hold a Ph.D. in Geochemistry from the Massachusetts Institute of Technology and several honorary degrees, including Doctor of Science degrees from Berea College and from Oberlin College. I taught Geology at Oberlin College for over 20 years.

I served as Acting President of Oberlin, President of Franklin and Marshall College, President of Reed College, President of the Franklin Institute Science Museum in Philadelphia, and President and Director of the Los Angeles County Museum of Natural History. President Ronald Reagan and later, President George H. W. Bush, appointed me to the National Science Board, where I served for 12 years. Asteroid 9739 Powell is named for me. In 2015 I was elected a Fellow of the Committee for Skeptical Inquiry (CSI).

I have written a number of books, the most recent of which is Deadly Voyager: The Ancient Comet Strike That Changed Earth and Human History. I also contributed to The Universe As It Really Is from Columbia University Press.

I am Executive Director of Graduate Fellowships for STEM Diversity.

The honor of which I am most proud is that my former student and friend, the late Rick Black, and his wife Robin, donated funds to build a new geology laboratory named for me at Oberlin College. As I said at the dedication, to be recognized for teaching at a school that exemplifies excellence in teaching is as good as it gets.