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污染:西非非法倾销

污染是指使土地、空气或水变脏。因此,它们可能有毒或无法使用,在某些情况下可能对人类健康构成危险。非洲每年产生190万吨垃圾,这实际上是很少的

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为什么河底的岩石常常是圆的?为什么暴雨过后湖泊通常会变得泥泞?谷是如何形成的?所有这些问题的答案都是侵蚀,这种过程使岩石和土壤从一个地方到另一个地方构成地球表面。侵蚀不断地改变景观的形状,并且可以由诸如水,空气甚至冰的天然元素引起的,倾向于从上部位置流到另一个冰。水可能是导致侵蚀的最强大的力量。如果水是泥泞的,这是一个侵蚀的标志。棕色表示岩石和土壤的位悬浮在水中并被运输。它行为的方式是: - 河流:他们在底部分解粒子并将其携带下游(例如大峡谷)。- 降雨:雨击中地球表面(飞溅侵蚀)或累积和流动作为小型溪流。 – Floods: they act very quickly as powerful rivers and the erosion rates are greatly accelerated. – Ocean waves: cause rock and coastline to break off changing the coastline over time. Erosion happens faster when shingle is thrown against the cliffs by the waves. In dry regions as deserts (e.g., Sahara, Atacama) wind is the most frequent agent of erosion because there are few plants to hold the soil in place and there is no rain to bind the soil particles together. It erodes in two ways: – Deflation: wind forces pick up and carry loose particles and dust away. – Abrasion: flying particles strike the land and break off more particles. Sometimes in mountain environments as Himalayas, Andes, but also near the North and South Poles, giant masses of ice that slowly move called glaciers, can carve out valleys and shape mountains. However, there are other minor forces that can cause erosion and these include: living organisms (i.e., insects, small animals, worms) can speed the erosion process by breaking up the soil and thus the water and/or wind can act on the surface more quickly; an increase of temperature may heat up a rock. This can lead the rock to expand, crack and break off in pieces over time; the force of gravity can pull rocks and other particles down the side of a mountain or cliff in form of landslides causing erosion. COULD HUMANS CAUSE EROSION? Erosion is a natural process, but human activity can make it happen more quickly. Humans have increased the rate of erosion through farming, ranching, cutting down forests, and the building of roads and cities. However, it is possible to control this phenomenon planting trees around farmland to protect it from the wind, moving herds around so that grasslands will grow back, and planting new trees to replace the ones cut down.

为什么河底的岩石常常是圆的?为什么暴雨过后湖泊通常会变得泥泞?谷是如何形成的?所有这些问题的答案就是侵蚀,这一过程移动了构成地球表面的岩石和土壤

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