雅思閱讀背景知識之塵暴區(qū)Dust Bowl

雅思閱讀背景知識之塵暴區(qū)Dust Bowl為大家?guī)?a href="http://pm4x.cn/ielts/" target="_blank" class="keylink">雅思閱讀中關(guān)于地質(zhì)學話題的一篇閱讀文章的背景解析，主要內(nèi)容為地質(zhì)學中一種叫做塵暴現(xiàn)象的科普，這個經(jīng)常出現(xiàn)塵暴的地區(qū)也叫做Dust Bowl，塵暴區(qū)。下面就讓我們一起來看看。

這篇雅思閱讀背景材料主要討論的是Dust Bowl也就是風沙中心的問題，也是美國中部大平原南部地區(qū)的代號。這個地區(qū)為什么會有這樣的一個代號呢，有什么特點呢?

Dust Bowl, common name applied to a large area in the southern part of the Great Plains region of the United States, much of which suffered extensively from wind erosion during the 1930s. The area included parts of Kansas, Oklahoma, Texas, New Mexico, and Colorado. In its original state, the region was covered with hardy grasses that held the fine-grained soil in place in spite of the long recurrent droughts and occasional torrential rains characteristic of the area. A large number of homesteaders settled in the region in the 30 years before World War I, planting wheat and row crops and raising cattle. Both of these land uses left the soil exposed to the danger of erosion by the winds that constantly sweep over the gently rolling land. Beginning in the early 1930s, the region suffered a period of severe droughts, and the soil began to blow away. The organic matter, clay, and silt in the soil were carried great distances by the winds, in some cases darkening the sky as far as the Atlantic coast, and sand and heavier materials drifted against houses, fences, and barns. In many places 8 to 10 cm (3 to 4 in) of topsoil were blown away. Many thousands of families, their farms ruined, migrated westward; about a third of the remaining families had to accept government relief.

塵暴是美國大平原地區(qū)南部一大片地區(qū)的統(tǒng)稱，在20世紀30年代，這些地區(qū)的大部分地區(qū)都遭受了風蝕。該地區(qū)包括堪薩斯州、俄克拉荷馬州、德克薩斯州、新墨西哥州和科羅拉多州的部分地區(qū)。在最初的狀態(tài)下，該地區(qū)覆蓋著耐寒的牧草，盡管該地區(qū)經(jīng)常發(fā)生干旱和偶爾的暴雨，但這些草保持了土壤的細粒性。在第一次世界大戰(zhàn)前的30年里，大量的莊園主定居在這個地區(qū)，種植小麥、種植莊稼、養(yǎng)牛。這兩種土地用途都使土壤暴露在風的侵蝕下，風不斷地吹拂著平緩起伏的土地。從20世紀30年代初開始，該地區(qū)遭受了一段時間的嚴重干旱，土壤開始流失。土壤中的有機物、粘土和淤泥被風帶到很遠的地方，有時甚至使大西洋海岸的天空變暗，沙子和更重的物質(zhì)被吹到房屋、籬笆和谷倉上。在許多地方，8到10厘米(3到4英寸)的表土被風吹走了。成千上萬的家庭，他們的農(nóng)場被毀，向西遷移;剩下的三分之一的家庭不得不接受政府的救濟。

Beginning in 1935 intensive efforts were made by both federal and state governments to develop adequate programs for soil conservation and for rehabilitation of the Dust Bowl. The measures taken have included seeding large areas in grass; 3-year rotation of wheat and sorghum and of lying fallow; the introduction of contour plowing, terracing, and strip planting; and, in areas of greater rainfall, the planting of long “shelter belts” of trees to break the force of the wind. Dry spells in the 1950s, '60s, and late '70s were responsible for recurrences of dust storms in the region.

從1935年開始，聯(lián)邦政府和州政府都在加緊努力，為土壤保護和沙塵暴的恢復制定適當?shù)挠媱?。采取的措施包括在大面積的草地上播種;小麥、高粱輪作三年，休耕三年;引入等高線耕作、梯田和條帶種植;而且，在降雨量較大的地區(qū)，種植長長的“防護林”來抵御風力。20世紀50年代、60年代和70年代末的干旱期是該地區(qū)沙塵暴復發(fā)的原因。

In the 1930s and 1940s, the region also received two waves of major migrations: that of farm families from the southern Great Plains migrating west to escape the Dust Bowl, and that of African Americans moving out of the American South. During World War II (1939-1945) the need for labor, especially in ship and aircraft production, boosted the population even more. The population of Los Angeles County jumped from 3 million to 4.7 million between 1940 and 1950.

20世紀30年代和40年代，該地區(qū)還經(jīng)歷了兩波大規(guī)模移民潮:一波來自大平原南部的農(nóng)民家庭為了躲避沙塵暴向西遷移，另一波來自美國南部的非洲裔美國人。在第二次世界大戰(zhàn)(1939-1945)期間，對勞動力的需求，尤其是對船舶和飛機生產(chǎn)的需求，進一步增加了人口。從1940年到1950年，洛杉磯縣的人口從300萬猛增到470萬。

以上就是雅思閱讀背景知識之塵暴區(qū)Dust Bowl的全部內(nèi)容，像地質(zhì)學這樣的專業(yè)性很強的文章，同學們更應該事先對背景知識進行掃盲。