Mountainous terrain and the relatively flat surface of the Rio Grande Rift Valley are featured in this photograph of south-central Colorado and north-central New Mexico. On the eastern side of the snow-covered Sangre de Cristo Mountains, two distinct drainage patterns show the Canadian River tributaries that drain southeast from the mountains and the headwater area for the Purgatoire River, which flows northeast and eventually merges with the Arkansas River. Meandering across the plains of the San Luis Valley is the narrow, dark Rio Grande, on either side of which appear several volcanic domes in various stages of erosion as identified by their radial drainage patterns. Dark Sanchez Reservoir appears north of the Colorado-New Mexico border (middle of the photograph).