Below are some links to related web pages and source information.

Volcano Hazards Program home page  - U.S. Geological Survey

Christiansen, R.L., Clynne, M.A., and Muffler, L.J.P., 2002, Geologic map of the Lassen Peak, Chaos Crags, and Upper Hat Creek area, California: U.S. Geological Survey Geologic Investigations Series I-2723, 17 p., 1 plate, scales 1:24,000, 1:2,500.

Clynne, M.A., 1984, Stratigraphy and major element geochemistry of the Lassen Volcanic Center, California: U.S. Geological Survey Open-File Report 84-224, 178 p.

Clynne, M.A., Muffler, L.J.P., Siems, D.F., Taggart, J.E., Jr., Bruggman, Peggy, 2008, Major and EDXRF trace element chemical analyses of volcanic rocks from Lassen Volcanic National Park and vicinity, California: U.S. Geological Survey Open-File Report 2008-1091, 10 p.