Mammoth

The Caldera. Long Valley Caldera a 15- by 30-km oval-shaped depression located 20 km south of Mono Lake along the east side of the Sierra Nevada in east-central California. This area of eastern California has produced numerous volcanic eruptions over the past 3 million years, including the massive caldera-forming eruption 760,000 years ago. The most recent eruption occurred just 250 years ago in Mono Lake at the north end of Mono-Inyo Craters volcanic chain.

Volcanic Unrest. In May of 1980, a strong earthquake swarm that included four magnitude 6 earthquakes struck the southern margin of Long Valley Caldera associated with a 25-cm, dome-shaped uplift of the caldera floor. These events marked the onset of the latest period of caldera unrest that continues to this day. This ongoing unrest includes recurring earthquake swarms and continued dome-shaped uplift of the central section of the caldera (the resurgent dome) accompanied by changes in thermal springs and gas emissions.

Devils Postpile National Monument

Oblique aerial view west across Owens Valley in Lone Pine 15' quadrangle. In distance, Sierra Nevada, capped by Mount Whitney (elev. 14,494 ft; 4,418 m). In middle distance, Alabama Hills, town of Lone Pine, and Owens River. In foreground, Kern Knob, at base of Inyo Mountains. Movement along Owens Valley Fault Zone, at base of Alabama Hills, caused great Lone Pine earthquake of 1872 (estimated Richter magnitude about 8). From U.S. Geological Survey photograph GS–OAI–5–13, taken November 25, 1955.

1872 Lone Pine earthquake

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Lone Pine fault scarp

The Great Lone Pine earthquake was one of the largest earthquakes to hit California in recorded history. The quake struck on March 26, 1872 and its epicenter was near Lone Pine, California in Owens Valley. The true size of this earthquake is not known, but historical evidence detailing the damage it caused in settlements and landforms near the epicenter and the geographic extent to which noticeable movement was felt, leads researchers to estimate a Richter magnitude of 7.6 to 8 or greater - similar in size to the 1906 San Francisco earthquake.

The quake hit at 2:35 in the morning and leveled almost all the buildings in Lone Pine and nearby settlements. Of the estimated 250-300 inhabitants of Lone Pine, 27 are known to have perished and 52 of the 59 houses were destroyed. One report states that the main buildings were thrown down in almost every town in Inyo County. About 100 kilometers south of Lone Pine, at Indian Wells, California, adobe houses sustained cracks. Property loss has been estimated at $250,000 (1872 dollars). As in many earthquakes, adobe, stone and masonry structures fared worse than wooden ones which prompted the closing of nearby Camp Independence which was an adobe structure destroyed in the quake.