Just East of the San Juan Mountains lies the San Luis Valley, a spacious 7,500-foot-high mountain grassland. But geologically, the San Luis Valley is also an extraordinarily deep hole. Unlike Colorado’s North, Middle and South Parks, much of the San Luis basin formed as the Earth’s crust stretched apart along the Rio Grande Rift 25 million years ago. As the basin dropped, erosion from the surrounding mountains kept filling it with rock and sediment. In fact, portions of the San Luis Valley's fill sediment may be nearly 30,000 feet deep. Thus underneath the San Luis valley surface lies one of Colorado’s deepest filled holes
Growing Home: The San Luis Valley
