Field Trip leader Jama Crawford will explain the treasures this valley conceals. The San Luis Valley is a true rift valley with faults that penetrate the Earth's crust all the way to the mantle. River re-routing and plunging rift effects left the valley north of the modern Rio Grande River high ... but not dry. Snow melt flows in, but not out, and the valley features over 120,000 acres of wetlands. This gave rise to the largest intermountain waterfowl migration in the U.S. We will bear witness to this breathtaking migration, while learning about the geology that supports it. Our focus will be on 20,000 Sandhill Cranes, the largest and most entertaining of the valley's avian visitors, so bring binoculars and a camera. Most activity takes place on Sat March 12 (a day trip is possible but involves 5 hours round trip driving and returning home after dark) but several side trips are planned for Mar 11 and 13 if you can stay over. Lodging is in short supply so find a hotel room quickly preferably near Monte Vista, where we will meet. Heated camper trailers, trucks and vans should be able to handle overnight temperatures (in low 20s) but this is not a tenting weekend.