Volcanic activity to the south produced giant fissures, or earthcracks, throughout the Wupatki area in the Kaibab Limestone, a formation that covers most of the western half of Wupatki National Monument. The Sinagua and Anasazi Indians who inhabited these ancient pueblos probably found the earthcracks to be the most productive farming sites. With no evidence of nearby streams that could be used for water, farming depended on rainfall. Corn, squash, and other crops were planted along canyon slopes and wash bottoms, and small check dams along drainage courses provided level areas for farming. These flat areas retained more moisture, and the accumulated silt enriched the soil. The bottom of Box Canyon below the ruins may have been an ideal farming area. Juniper, amaranth, yucca, Indian rice grass, and other native plants were used as food, along with antelope, rabbit, squirrels, packrats, and reptiles.