File:Sandy River (Old Maid Flat, west of Mt. Hood Volcano, Oregon, USA) 1 (20022316292).jpg
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| Description |
(22 October 2009) Looking upstream. This is the Sandy River, an important drainage that heads westward from Mt. Hood Volcano in northwestern Oregon. The forested flats on either side of the river are part of Old Maid Flat, which dates to the last couple hundred years. The forest is underlain by Mt. Hood lahar deposits, dating to 1781-1801 A.D. Lahars are usually simply defined as volcanic mud flows (water mixed with volcanic ash moving downslope as a thick slurry), but they frequently contain abundant large clasts. The gravel and sand present along the river are derived from the adjacent lahar deposits and composed of Mt. Hood volcanic lithologies (high-silica porphyritic andesites & low-silica porphyritic dacites). There is virtually no soil present between the Old Maid Flat lahars and the overlying forest - a couple hundred years is not enough time for decent soil development. Mt. Hood's volcanic activity from 1781 to 1801 is called the Old Maid eruptive phase. An eruption occurred in 1781 after the end of the growing season. Dome building occurred from 1781 to 1793. Another Mt. Hood eruption occurred in 1800. The gravel bars present along the Sandy River when this photo was taken were deposited during a flood event in 2006, the result of 25 inches of rain in three days on Mt. Hood Volcano. Locality: Old Maid Flat, northwestern side of Zigzag Mountain, northeast of Mt. Hood Village & west of Mt. Hood Volcano, northeastern Clackamas County, northwestern Oregon, USA |
| Date | |
| Source | Sandy River (Old Maid Flat, west of Mt. Hood Volcano, Oregon, USA) 1 |
| Author | James St. John |
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This image was originally posted to Flickr by James St. John at https://flickr.com/photos/47445767@N05/20022316292 (archive). It was reviewed on 28 January 2020 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-by-2.0. |
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| Date/Time | Thumbnail | Dimensions | User | Comment | |
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| current | 02:06, 28 January 2020 | | 3,002 × 1,918 (3.39 MB) | Ser Amantio di Nicolao (talk | contribs) | Transferred from Flickr via #flickr2commons |
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