Lightning Spalling

Of interest to archaeologists is a recent paper by J. D. Laudermilk and T. G. Kennard on the little known subject of lightning as an agent of weathering of exposed rocks. As a locality for field study of this natural phenomenon, they chose an area in the Mohave Desert near Yermo, California, which is known as a place of a great deal of electrical display. Here they found rocks of various sizes and materials, such as jasper, silicified lava, chalcedony, rhyolite, and quartzite. Many of these had apparently been split by some force other than great fluctuations of temperature, or by man in the production of stone artifacts. A great abundance of flakes and spalls was found on the ridges, usually in more or less circular or oval areas from one foot to five feet in radius. From the arrangement of these fragments it appeared that they had been spread from a common center in each of the areas.