What was the origin of the oil which now drives our motor-cars and aircraft? Scientists are confident about the formation of coa

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问题     What was the origin of the oil which now drives our motor-cars and aircraft? Scientists are confident about the formation of coal, but they do not seem so sure when asked about oil. They think that the oil under the surface of the earth originated in the distant past, and was formed from living things in the sea. Countless billions of minute sea creatures and plants lived and sank to the sea bed. They were covered with huge deposits of mud, and by processes of chemistry, pressure and temperature were changed through long ages into what we know as oil. For these creatures to become oil it was necessary that they should be imprisoned between layers of rock for an enormous length of time. The statement that oil originated in the sea is confirmed by a glance at a map showing the chief oilfields of the world; very few of them are far distant from the oceans of today. In some places gas and oil come up to the surface of the sea from its bed. The rocks in which oil is found are of marine origin too. They are sedimentary rocks, rocks which were laid down by the action of water on the bed of the ocean. Almost always the remains of shells, and other proofs of sea life, are found close to the oil. A very common sedimentary rock is called shale, which is a soft rock and was obviously formed by being deposited on the sea bed. And where there is shale there is likely to be oil.
    Geologists, scientists who study rocks, indicate the likely places to the oil drillers. In some cases oil comes out of the ground without any drilling at all and has been used for hundreds of years, In the island of Trinidad the oil is in the form of asphalt, a substance used for making roads. Sir Walter Raleigh visited the famous pitch lake of Trinidad in 1595; it is said to contain nine thousand million tons of asphalt. There are probably huge quantities of crude oil beneath the surface.

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答案 我们现在开汽车、飞机使用的石油是怎样形成的呢?科学家对解释煤的成因已很有把握,但若是被问到石油是怎样形成的,他们似乎就不那么有把握了。他们认为地底下的石油在远古时期就已经开始形成,而且是由海中生物形成的。无数亿个微小动物和植物在海水中生长并沉人海底,上面覆盖着大量沉积的泥沙。由于化学变化、压力和温度等因素影响,经过漫长的岁月,就形成了我们现在所说的石油。这些小动物必须在一层层岩石之间密封起来,经过极长的一段时间才能变成石油。“石油是在海里形成的”这一说法,只要看一下世界主要油田的分布图,就可以得到证实:只有极少数大油田是远离今天的海洋的。在有些地方,天然气和石油从海底升上海平面。含有石油的岩层也是在海里形成的。这种岩层是沉积岩,是在海水的作用之下沉积在洋底的。在有石油的地方附近,几乎总可以发现贝类的残骸以及海洋生物的其他遗迹。有一种非常常见的沉积岩叫做页岩,这种页岩非常柔软,而且很明显是由于长期沉积在海底而形成的。有页岩的地方就很有可能存在石油。 地质学家,也就是研究岩石的科学家,为石油钻探者指明了可能的地点。有时候石油会直接渗出地面,无需钻探。石油的使用已经有上百年的历史了。在特立尼达拉岛,石油以沥青的形式呈现,沥青是用来铺路的材料。瓦尔特?罗里爵士曾经于1595年参观过特立尼达拉岛著名的沥青湖,据说湖中贮有九亿吨沥青。地下可能还有大量的原油。

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