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They provided volumes of rich observations and findings that established both geographic knowledge and methodological precedent for future explorations and surveys of the West. This included evidence of extensive continental and alpine glaciation, growth and shrinkage of huge ice-age lakes, and episodes of volcanism, mountain building, and canyon cutting.In the spring of 1804, however, when Lewis and Clark headed west, geology was hardly an established science. Within the newly formed USGS were Emmons, John Wesley Powell, Clarence E. More than just documenting the geologic history of the West, these geologists and geographers also developed key concepts of landscape formation.
In their landscape and hydrographic descriptions, Lewis and Clark recorded effects of several different "cataclysms on the Columbia," a phrase John Allen used for the title of his 1986 book on the ice-age Missoula floods.
Geologic cataclysms affecting the Columbia River Gorge, however, include more than the gigantic floods of fifteen to seventeen thousand years ago. In addition to shooting through the narrows at The Dalles of the Columbia, perhaps a remnant of the great ice-age floods, Lewis and Clark drifted past a submerged forest and portaged Cascade Rapids, the result of a huge landslide only three hundred and fifty years before their exploration.
Travelers retracing Lewis and Clark’s journey to the Pacific over the past two hundred years have witnessed tremendous change to the Columbia River Gorge and its primary feature, the Columbia River.
Dams, reservoirs, timber harvest, altered fisheries, transportation infrastructure, and growth and shrinkage of communities have transformed the river and valley.
This radically different geography of human use and habitation is commonly contrasted with the sometimes romantic view of a prior time provided both by early nineteenth-century chroniclers and present-day critics of the modern condition—an ecotopia of plentiful and perpetual resources sustaining a stable culture from time immemorial. Certainly the human-caused changes to the Columbia River and the gorge since Lewis and Clark have been profound; but the geologic history of immense floods, landslides, and volcanic eruptions that occurred before their journey had equally, if not more, acute effects on landscapes and societies of the gorge.
In many ways, the Lewis and Clark Expedition can be viewed as a hinge point for the Columbia River, the changes engineered to the river and its valley in the two hundred years since their visit mirrored by tremendous changes geologically engendered in the thousands of years before.