You're near the top of fourteener Mount Elbert, and dark clouds are creeping in. Do you keep climbing or turn back? Ask Colorado geologist Jack Reed, when he presents his new book, Rocks Above the Clouds: A Climber's Guide to Colorado Mountain Geology, this weekend. The author and long-time member of the Colorado Mountain Club has written books about geology in the Appalachians, Tetons, and Alaska Range. He knows how rocks react not only when they're wet, but also when they're exposed to weight and wear. Sat, Mar. 7, 2 p.m. Tattered Cover Historic LoDo, 1628 16th St. 303-436-1070, Free