From the scientific perspective:

     Hogwallows. Mima Mounds. Pimpled Plains. All are names of similarly described land formations existing in great numbers in many locations in North America, South America, and Africa. In the United States the principal locations of these mounds are from Missouri to southern Texas, the plateau regions of Colorado, the northwestern states, and the Great Central Valley and southern coastal regions of California. In 1966, some 665 acres of mima mounds near Little Rock, Washington, were protected under the National Natural Landmark program of the National Park Service.

     Soil scientists around the world have spent untold hours studying these mounds and swales, resulting in more than 30 theories being posited to explain what caused their formation. These range from earthquake or glacial action, to ancient fish nests, to flooding due to giant tsunamis raised by asteroid impacts at sea. Nevertheless, their origin remains an unsolved mystery.

     One of the dominant theories of their formation is that the mounds are the work of pocket gophers, as cited in an article in “Soil Science Society Proceedings 1954,” by Rodney Arkley and Herrick Brown of the Soils Department of the University of California, Berkeley. After extensive study of hogwallows in the Merced area, they concluded that “the pocket gopher is responsible for the mounds, but he builds them only on soils where the thickness of soil is suitable for burrowing and root growth is restricted.” Thus, generation after generation of gophers, from the prehistoric to the present day, may keep building nests near the crest of any high spot in the land surface, forming the characteristic hogwallow mounds above the hardpan swales.*

     * See also: https://www.science.org/content/article/mima-mound-mystery-solved

     From the Native American Perspective:

     As part of the Creation Story related to historian Frank Latta by a Wukchumni (Yokut), this is how the hogwallows were formed: In the very old days, after the Eagle made the world, there was only Tulare Lake and the plains. Eagle called the People and told them to build a new place for him. The People got together to build high mountains for Eagle. They used their carrying baskets to take the dirt from the San Joaquin Valley and pile it up to make the mountains. When Eagle saw that the mountains were high enough to have snow on their tops, he called to the People to stop. The People took their baskets off their backs and emptied the remaining dirt onto the ground, making the little round mounds that White People call Hogwallows. The Wukchumni word for hogwallows is Pawkawkwitch.

June, 2013