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Lassen Volcano | John Seach
California, USA
40.49 N, 121.50 W
summit elevation 3187 m
stratovolcano
Lassen volcano is located in northern California, at the southern end of the Cascade Range. Many of the volcanic features are located in the Lassen volcanic National Park.
The volcano consists of an andesitic stratovolcano, a dacite dome field, and small andesite shield volcanoes. The 1914-17 eruptions of Lassen peak was the first of only two volcanoes to erupt in the continental USA in the 20th century.
1992 Earthquakes
On 28th June 1992 a magnitude 7.5 earthquake occurred 800 km SSE of
the volcano. A magnitude 2.8 earthquake was recorded at Lassen Peak
10 minutes after the arrival of the S wave from the tectonic
earthquake. A total of 22 earthquakes were recorded at Lassen
volcano in the first 24 hours.
1914-17 Eruption
An eruption began on 30th May, 1914 with a phreatic explosion at the
summit of Lassen Peak. An eruption on 22nd May 1915 devastated an
area of 7 sq km on the NE of the volcano. Lahars descended Lost
Creek, with minor lahars flowing down valleys on the west, northwest
and north flanks of the volcano. The lahar was triggered by melting
of snow by pyroclastic flows.
On 12th June 1914, a climbing group of five people were caught half a mile from the crater during an eruption. Milton Ayres, a San Francisco movie camer operator described the event.
"We had no warning. The roar and the uprush of the black mass
above were simultaneous. The rocks began to fall on the mountain
side; the gases did not come our way much, as the wind drove them
to the east, but we got some strong whiffs of sulphur smoke. For
the same reason little ash fell where we were. Later we went on to
the summit, reaching it at 6 P. M., two hours after the eruption
began. We found the whole mountain top strewn with great boulders
and heavy ash. No one could possibly have lived at the top while
the outburst was on. We climbed up to the shelter house, where we
had expected to spend the night, and found it in ruins. Boulders
had crashed down through it and splintered the building to
kindling wood."
Further Reading
Clynne, M.A., Robinson, J.E., Nathenson, M. and Muffler, L.P., 2012. Volcano hazards assessment for the Lassen region, northern California (p. 47). US Department of the Interior, US Geological Survey.
Klein, F.W., 1979. Earthquakes in Lassen Volcanic National Park, California. Bulletin of the Seismological Society of America, 69(3), pp.867-875.
MacDonald, G.A. and Katsura, T., 1965. Eruption of Lassen Peak, Cascade Range, California, in 1915: example of mixed magmas. Geological Society of America Bulletin, 76(5), pp.475-482.
Lassen Volcano Eruptions
1914-17, 1650?