地理教學 geography teaching

冰河外洗平原 為何外圍還有風積黃土

我們先看百科英文的解釋

Glacial loess is derived from the floodplains(冰河外洗平原) of glacial braided rivers that carried large volumes of glacial meltwater and sediments from the annual melting of continental icesheets and mountain icecaps during the summer. During the fall and winter, when melting of the icesheets and icecaps ceased, the flow of meltwater down these rivers either ceased or was greatly reduced. As a consequence, large parts of the formerly submerged and unvegetated floodplains of these braided rivers dried out and were exposed to the wind. Because these floodplains consist of sediment containing a high content of glacially ground flour-like silt and clay, they were highly susceptible to winnowing of their silts and clays by the wind. Once entrained by the wind, particles were then deposited downwind. The loess deposits found along both sides of the Mississippi River Alluvial Valley are a classic example of glacial loess.^[

^{冰河外洗平原下有一些淤泥與泥土 受到風吹的作用日久了就形成了風積黃土}