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Table Mountain, Washington, as seen from Hamilton Island, Washington, with part of the Bonneville Landslide in the foreground.
Image taken February 19, 2013.
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Table Mountain ...
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Table Mountain is located on the Washington side of the Columbia River and rises above North Bonneville,
the
Bonneville Dam, and Cascade Locks, Oregon.
Downstream of Table Mountain is Aldrich Butte and Hamilton Mountain and upstream is Rock Creek and Stevenson, Washington.
Table Mountain is part of the massive Bonneville Landslide event which formed the Cascade Rapids, a major barrier to early travelers on the Columbia River. Lewis and Clark reached this area in October 1805 and had to portage around the rapids.
Magnificent views of Table Mountain and it's companion to the northeast, Greenleaf Peak, are visible from many areas along the Columbia. Cascade Locks, on the Oregon side of the Columbia, has perhaps the best view of Table Mountain. Other good views are from Bonneville Dam and North Bonneville, Washington.
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Table Mountain and the Bonneville Landslide, Washington, as seen from Cascade Locks, Oregon.
View towards the location of Lewis and Clark's campsites of October 30 and 31, 1805 and April 12, 1806, near Ashes Lake, Washington, at the upper end of the Bonneville Landslide. View from Thunder Island, Cascade Locks, Oregon.
Image taken November 4, 2004.
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Lewis and Clark and Table Mountain ...
Lewis and Clark reached the Table Mountain area on October 30, 1805, and set up camp near Ashes Lake, just upstream of the "Cascade Rapids" and across from today's Cascade Locks, Oregon.
Table Mountain rises over the area. From this camp the men took two days to portage down through the Cascade Rapids.
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Bonneville Landslide ...
Table Mountain is part of the massive Bonneville Landslide event which formed the Cascade Rapids, a major barrier to early travelers on the Columbia River.
The Bonneville Landslide is one of the greatest landslides along the Columbia River, diverting the river channel a mile, and creating the legend of the Bridge of the Gods.
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Table Mountain, Greenleaf Basin, and Greenleaf Peak, Washington, as seen from Cascade Locks Marina, Cascade Locks, Oregon.
Image taken May 20, 2011.
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Columbia River Basalt Group ...
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"Flood basalts of the Miocene Columbia River Basalt Gorup (CRBG) are among the most volumninous and far-traveled lava flows on earth. About 10% of the basalt flows that erupted on the Columbia Plateau between 17 and 12 Ma were voluminous enough to pass through the Cascade arc via a wide ancestral Columbia River valley, and some of them eventually reached the Pacific Ocean. Some of the larger flows invaded the marine strata, forming mega-invasive flows on the continental shelf and slope. ...
The basic geologic framework of the Columbia River Gorge has been known for over a century. In the western gorge, the package of Columbia River Basalt Group (CRBG) flood-basalt flows unconformably overlies volcanogenic rocks of ancestral Cascade volcanic arc. Vigorous and widespread volcanism characterized the arc from its inception 40 Ma until ca. 18 Ma, when activity greatly declines. The arc must have been relatively quiescent during emplacement of the most voluminous CRBG flows, because interflow volcanic sediments are sparse. The larger flows passed through a 50-km-wide ancestral Columbia River valley on their way to the ocean. Owing to late Cenozoic uplift of the Cascade Range and resultant incision by the Columbia River, CRBG flows are now spectacularly exposed in the cliffs and waterfalls of the Columbia River Gorge. The modern gorge roughly follows the northern margin of the broad Miocene valley. Grande Ronde flows clearly abut the northern paleovalley wall formed by early Miocene volcaniclastic rocks of the 19 Ma Eagle Creek Formation.
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The slight southward dip of the Columbia River Basalt Group (CRBG) section and the underlying Eagle Creek Formation gives the western gorge an asymmetric physiographic cross section. In Washington, failure of weakly lithified Eagle Creek strata that dip toward the river under the load of superincumbent basalt has produced huge landslide complexes composed largely of CRBG debris. In Oregon, where strata dip away from the river, undercutting of the Eagle Creek Formation instead creates towering cliffs. As a result, the CRBG section south of the river consists of continuous cliffs, whereas to the north the CRBG forms scattered peaks (Greenleaf Peak, Table Mountain, Hamilton Mountain, and Archer Mountain) separated by low-lying terrain underlain by the Eagle Creek Formation or landslide debris. Each of these peaks is actually the southern end of a N-S ridge of CRBG, marking sites where basalt flows backfilled south-flowing tributaries of ancestral Columbia River."
Source:
Wells, R.E., Niem, A.R., Evarts, R.C., and Hagstrum, J.T., 2010, "The Columbia River Basalt Group -- From the gorge to the sea", IN: Geologic Society of America Field Guild 15, 2009.
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Views ...
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Table Mountain, Washington, from Robins Island, Oregon.
Image taken October 27, 2004.
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Table Mountain and Greenleaf Peak, Washington, as seen from downstream of Bonneville Dam, Oregon.
Image taken October 25, 2003.
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Table Mountain as seen from near the North Powerhouse, Bonneville Dam, North Bonneville, Washington.
Image taken March 21, 2014.
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Table Mountain, Washington, from Hamilton Island, Washington.
Image taken April 2, 2005.
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From the Journals of Lewis and Clark ...
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Clark, October 30, 1805 ...
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