English: The Potrillo volcanic field is one such testing ground. Located southwest of Las Cruces, New Mexico, and west of El Paso, Texas, Potrillo occupies more than 1,000 square kilometers (400 square miles) near the U.S. border with Mexico. Its parched lands are part of the Chihuahuan Desert, which covers much of northern Mexico and stretches all the way to Albuquerque. Potrillo is considered dormant now, with its last volcanic activity occurring about 20,000 years ago. Stained black by basalt, the area offers a smorgasbord of lava flows, craters, and cones from both explosive and effusive volcanoes. This diversity of volcanic features makes Potrillo appealing to planetary geologists.