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The Willamette Valley () is a long valley in the Pacific Northwest region of the United States, located entirely within the state of Oregon. The valley forms the cultural and political heart of Oregon and is home to approximately 70 percent of its population〔Loy, ''et al.'', p. 35〕 including Portland, its largest city, as well as Salem, the state capital. The Willamette River flows the entire length of the valley, which is surrounded by mountains on three sides - the Oregon Coast Range to the west, the Cascade Range to the east, and the Calapooya Mountains to the south. The valley's numerous waterways, particularly the Willamette River, remain vitally important to the economy of Oregon, as they continuously deposit highly fertile alluvial soils across its broad, flat plain. A massively productive agricultural area, the valley was widely publicized in the 1820s as a 'promised land of flowing milk and honey'. Throughout the 19th century it was the destination of choice for the oxen-drawn wagon trains of emigrants who made the perilous journey along the Oregon Trail.〔name=OT-II_stats>Figures summed from the detailed inter-landmark distances in the guidebook published with the highly researched educational Oregon Trail II computer game, Oregon Trail (computer game). These sum and agree with the trip totals during game play. Today the valley is often considered synonymous with "Oregon Wine Country", as it contains more than 19,000 acres of vineyards and 500+ wineries.〔http://willamettewines.com/facts-figures〕 ==Geology== Much of the Willamette’s fertility is derived from a series of massive ice-age floods that came from Lake Missoula in Montana and scoured across Eastern Washington, sweeping its topsoil down the Columbia River Gorge. When floodwaters met log-and-ice jams at Kalama in southwest Washington, the water caused a backup that filled the entire Willamette Valley to a depth of above current sea level.〔''Cataclysms on the Columbia'', by John Elliott Allen and Marjorie Burns with Sam C. Sargent, 1986. Pages 175–189.〕 Some geologists suggest that the Willamette Valley flooded in this manner multiple times during the last ice age.〔〔''Geology of Oregon'', by Elizabeth L. Orr, William N. Orr and Ewart M. Baldwin, 1964. Pages 211–214.〕 If floodwaters of that magnitude covered Portland (elevation ) in 2010, only the tops of the West Hills, Mount Tabor, Rocky Butte, Kelley Butte and Mount Scott would be visible,〔 as would only some of the city’s tallest skyscrapers. Elevations for other cities in the valley are Newberg, ; Oregon City, ; McMinnville, ; Salem, ; Corvallis, ; and Eugene, . The lake gradually drained away, leaving layered sedimentary soils on the valley floor to a height of about above current sea level throughout the Tualatin, Yamhill and Willamette valleys.〔 Geologists have come to refer to the resulting lake as Lake Allison, named for Oregon State University geologist Ira S. Allison, who first described Willamette Silt soil in 1953 and noted its similarity to soils on the floor of former Lake Lewis in Eastern Washington. Allison is also known for his work in the 1930s documenting the hundreds of non-native boulders (called erratics) washed down by the floods, rafted on icebergs and deposited on the valley bottom and in a ring around the lower hills surrounding the Willamette Valley. One of the most prominent of these is the Bellevue Erratic, just off Oregon Route 18 west of McMinnville.〔 It is also believed that the Willamette Meteorite was rafted by flood and ice to the location near West Linn where it was found in 1902. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Willamette Valley」の詳細全文を読む スポンサード リンク
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