Clear Lake, California, lies in a volcano-tectonic depression that received nearly continuous lacustrine deposition for the past 500,000 yr and probably longer. The lake has been shallow (<30 m) and eutrophic throughout its history. Sediments beneath the floor of the lake are fine grained (chiefly >7.0φ) and contain fossils of a large lacustrine biota, as well as a pollen record of land plants that lived in the basin. The sediments also contain tephra units of local and regional extent. The ages of the sediments in Clear Lake are determined from radiocarbon dates on the sediments, from correlation of regionally distrbuted...