Geologists like to make mountains by smashing things into continents, like India crashing into Asia made the Himalaya. The Colorado Rockies are different somehow: this area sank down into the ocean before popping up about 70 million years ago. But after being drowned from above, the crust in Colorado might also have been drowned from below, perhaps a unique process that might finally answer the question, why is Denver the Mile High City?
Craig has spent a career putting seismometers in odd spots to try and figure out how all the mountains in the western U.S. came to be. He's been a professor in geology at CU Boulder long enough to remember Crossroads Mall, cattle grazing where Flatiron Crossing is now, and CU having a consistently good football team. He is also the author of the book "The Mountains that Remade America: How Sierra Nevada Geology Impacts Modern Life".