IntroductionVolcanic activity has been largely non-explosive, with the exception of one major explosive eruption that must have occurred and deposited a airfall tuff. Most lavas found here range from basalt through rhyolite in composition, dacite being the most dominant type.
Eruptions at Clear Lake volcanic field:
4 eruptive episodes separated by time gaps of ca. 150-200,000 years have been recognized: 2.1-1.3 million years ago (m.y.), 1.1-0.8 m.y., 0.65-0.30 m.y., and 100,000-10,000 years ago. The total volume of about 100 individual eruptions exceeds 70 cubic kilometers.
Eruptive products from the first activity episode are found in the east of the field. The second activity episode constructed Cobb Mountain (1 million years, Ma) and Mount Hannah (0.9 Ma). The third episode of activity was at the Mount Konocti–Thurston Lake area, the most voluminous dacite and rhyolite feature of the Clear Lake volcanics.
The most recent activity, up to about 10,000 years ago were small mostly basaltic and andesitic eruptions in the north of the field.
Sources: GVP, NCGS (Northern California Geological Society)
See also: Sentinel hub | Landsat 8 | NASA FIRMS