Forrest Hopson
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Forrest Hopson
@rfh-geology.bsky.social
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Geologist
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rfh-geology.bsky.social
Asymmetric syncline and thrust fault in Miocene Monterey Formation near Los Prietos Boys Camp about 800 feet west of the first Santa Ynez River crossing along Paradise Road. Western Transverse Ranges. Photo location approximately 11S 244914E 3826258N Photo by RF Hopson.
April 6, 2025 at 1:07 AM
rfh-geology.bsky.social
Morongo Valley and Pinto Mountain Fault. Morongo Valley is a triangular-shaped transtensional graben bound by the Morongo Valley and Pinto Mountain Faults. Black line denotes the Pinto Mountain fault. Mt. San Gorgonio and San Bernardino Mountains in the distance. Photograph by R.F. Hopson.
February 17, 2025 at 1:54 AM
rfh-geology.bsky.social
Red Cinder Cones and Mount Hamilton from Cinder Cone. Painted Dunes and Fantastic Lava Beds in the foreground. The Painted Dunes may have formed when rain or snow fell on the ash while the Fantastic Lava Beds beneath it were still hot. Alternatively, the Painted Dunes may have formed when the lavas flows covering marshy ground around ancient Butte Lake generated steam to oxidize the ash. The Fantastic Lava Flows are five basaltic andesite and andesite flows erupted in quick succession from the base of Cinder Cone in 1666. Red Cinder, and Red Cinder Cone are cinder cones in the Caribou Volcanic Field. Red Cinder produced an andesite lava flow 69,000±20,000 years ago and a basaltic andesite flow estimated to be 25,000–40,000 years old. Red Cinder Cone produced basaltic andesite and basalt flows estimated to be 20,000–250,000 and 25,000–40,000 years old. Mount Hamilton is consists of predominately late Pliocene to early Pleistocene andesites that were erupted during Stage 1 of Dittmar Volcanic Center and is overlain by till estimated to be 8,000–35,000 years old. Photograph by R. Forrest Hopson.
February 17, 2025 at 12:13 AM
rfh-geology.bsky.social
The Terminal Geyser fault offsets regional basalt of Sifford Mountain about 11 feet (3.4 m) at this location. Blue pack for scale. Photograph by R.F. Hopson.
February 16, 2025 at 10:58 PM
rfh-geology.bsky.social
Brokeoff Mountain, Mount Diller and Lake Helen. View across the eroded core of Brokeoff Volcano. Brokeoff Mountain is underlain by andesites of Mill Canyon (470,000–590,000 years) and dacite of Twin Meadows (470,000±10,000 years), Mill Canyon sequence lava flows. Andesite of Mount Diller (387,000±10,000 years) makes up Mount Diller. Till of Anklin Meadows deposited by the glacier that created the Lake Helen cirque forms the shores of Lake Helen. The upper shores are outcrop. Photograph by R. Forrest Hopson.
February 10, 2025 at 2:00 AM
rfh-geology.bsky.social
Lassen Peak from Manzanita Lake. Lassen Peak is a 27,000±1,000-year-old dacite dome. Lassen Peak rises 2,000 feet (610 meters) above the surrounding countryside and has a volume of about 0.6 cubic miles (2.5 cubic kilometers) making it one of the largest lava domes on Earth. To the left of Lassen Peak is Dome B, a rhyodacite dome within the Chaos Crags group of domes (1,100 years). Eagle Peak, to the right of Lassen Peak, is a rhyodacite dome (66,000±4,000 years). These domes belong to the Eagle Peak sequence. Photograph by R. Forrest Hopson.
February 10, 2025 at 12:07 AM