The Columbia River takes a 180-degree bend where it becomes the border with Oregon (lower half of the view in this north-looking scene). The Snake River enters the view from the northeast (top right) and joins the Columbia just below Ice Harbor Dam. Two distinct patterns of land use can be seen in this photograph. The green signature of irrigated crops (potatoes, vegetables, fruits, and hops) appears on floodplains flanking these rivers. On higher-lying flat landscapes beyond the reach of easy irrigation, agriculture is “rainfed.” In this summer-dry, semiarid part of the United States (rainfall less than 200 millimeters), upland fields are dormant and therefore yellow-brown in this late summer (September 1994) view. Winter wheat from the Columbia Basin is the state's leading dryland crop.
Underlying much of this area is the Columbia Basin, a basin that is primarily filled with lava but is topped by sedimentary rocks. The erosive action of the Columbia River has cut through the sedimentary deposits and into the deeper lava deposits, which are visible as the dark gray to black areas flanking the river. In the recent geological past (13,000 to 18,000 years ago), a catastrophic flow of glacial meltwater originating northwest of this scene carved the nearby area.
September 1994, image STS-64-112-93.