Scattered lapilli of gray pumice are present at the ground surface on the south,
east, and northeast sides of Mount Hood, but nowhere do the lapilli form a
continuous layer. The largest fragment noted on the ridge 1.3 kilometers west
of Mount Hood Meadows was 1.9x2.5.2.3 centimeters in dimension, and one on a
ridge 1.5 kilometers north-northeast of Mount Hood Meadows was 3x4x5.5
centimeters. The lapilli are generally less than a centimeter in diameter in
the areas west of Timberline Lodge, along the East Fork Hood River valley, and
near Cloud Cap Inn. Ferromagnesian minerals in the pumice are hypersthene and
hornblende; augite is very rare. The chemical composition of a sample of the
pumice is given in appendix C.
-- (Web note: not currently online)
The recent pumice can be found on top of the pyroclastic flow of Old Maid age in the White River valley; thus, the pumice probably is less than 200 years old. The pumice may have been erupted during the middle of the 19th century. A minor eruption of Mount Hood in September 1859 was witnessed by W.F.Courtney (letter to Everett, Washington, Record, May 1902, quoted in Harris, 1976, p.147), who reported the following:
An event that was probably was another minor eruption of Mount Hood was witnessed in 1865 by John Dever, a soldier stationed at Fort Vancouver, Washington, 80 kilometers west-northwest of the volcano. He reported (letter to Portland Oregonian, September 26, 1865) that he saw between 5 and 7 a.m. on September 21,
Although the recent pumice that is scattered on the slopes of Mount Hood could have erupted in either 1859 or 1865, it also could be the product of more than one eruption. |
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