51. Example of pre-1886 craterlet in a drainage ditch. This (circular) craterlet, now filled and with a weathering profile imposed on the fill, formed from an earthquake about 1,250 yr BP. Ground surface at that time was about a half meter above the head of the viewer, at the top of the entrenching shovel. The white material in the lower two-thirds of the outcrop is clean, medium- to fine-grained sand, which comprised a beach ridge about 100,000 years ago. The upper third of the outcrop (the black portion) is a humate-cemented sand, except for the filled craterlet. A schematic depiction of this photograph is given in the next slide.