The sealed oven. Not shown is the addition of a second layer of prickly pear pads above the lechuguilla layer. The plant materials are then covered with a thick layer of earth, which seals the oven, creating a steamy, anaerobic environment. If the oven is properly constructed, the steam maintains the temperature of the lechuguilla at very near 100 C (boiling temperature) for many hours. Photo by Phil Dering.