Broken glass and pottery mark the surface of a 100-year old dump on the eastern shoreline of San Francisco Bay. Bone, shell, and stone found in a unit at Fort Ross. The bone and shell are the remains of people's meals. The broken stones were used for cooking. Middens are normally dark in color, and include charcoal, ash, animal bones, and artifacts.
Middens are similar to backyard compost piles, but are much larger in size.
In an archaeological site, these layers often reveal how the site was formed. Left, Two thousand years of stratigraphy visible in walls of excavation unit at Lake Sonoma. Right, Stratigraphy visible in creek bank, eastern San Francisco Bay area. The dark layer is a midden created by California Indians more than 5,000 years ago. Features include bedrock mortars, graves, foundations of old buildings, and roads.