很多考生会抱怨托福阅读时间不够，还没完全理解文章就做题，正确率不高。其实这是我们对托福阅读素材不熟悉造成的，下面小编整理了一下托福阅读考试最新的素材，希望能帮助大家更加快速高效的备考托福。

　　托福阅读素材：地球上的海洋是如何出现的

　　内容回忆：

　　第 1 段讲到如果要了解地球上海洋的起源，需要先了解太阳系是如何形成的。太阳系是 dust 爆炸之后形成了一个个 clump, 比较大的 clump 因为重力会吸引那些小一些的行星及其它物质。而且重量越大，速度越快。 然后这些较大的 clump 就会成为 embryo planets. 地球就是在这种条件下行成的。一开始假设地球是 cold 低温的，所以 urnanium 等放射性物质挥发的时候，就会让水形成并从 volcano 中喷发而出，于是形成了海洋。

　　第 2 段讲到该理论有些问题。问题之一是就是目前的发现表明没有那么多的火山喷发以形成今天这么广阔的海洋。第二就是该理论是以一个错误的观点为基础的。因为根据太阳系的行成原因，地球不可能以那么温和缓慢的方式行程，在比较高速的情况下，那么地球一开始的温度就是高的，而不是 cold.

　　参考阅读：

　　It has been found that the frozen ocean of the North (for how long could it be still named so?) has its origins in ... a lake. 20 million years ago, what is now the Arctic Ocean was just a very large lake, whose fresh water flew southwards through a narrow strait into the Atlantic.

　　But 18.2 million years ago, the tectonic plates started to move and the strait started to get larger. Slowly, during probably 750,000 years, salt water from the Atlantic entered the Arctic transforming it into the current ocean. A Swedish team led by Martin Jakobsson at Stockholm University in Sweden,analyzing the first core of sediments from the bottom of the Arctic Ocean extending for the past 53 million years, extracted in 2004, reached this conclusion.

　　The 5.6 m (19 ft) long segment dated 18.2 to 17.5 million years ago was different: it was located over a layer of gray silt containing freshwater fossils (pointing to a lake), and within it, the mud had three very distinct bands of color: one made of thin lines of black and gray silt, one of gray sediment and a brownish layer.

　　The thin black silt lines are rich in an organic matter which is not decomposed, from a period when the bottom of the lake was poorly oxygenated and the organic matter did not degrade.

　　"As the Fram Strait, wedged between Greenland to the west and the Norwegian archipelago of Svalbard to the east, began opening up 18.2 million years ago, the large Arctic lake went through an estuarine phase. We suspect that there was a flow very similar to the Black Sea, with fresh water flowing out of the Arctic on the surface, and heavier salt water flowing in underneath," said Jakobsson.

　　The heavier salt water lacked oxygen, settling on the bottom of the ancient lake, killing all organisms and leaving the layers of black anoxic silt. Still, this did not occur in a smooth way.

　　"This is why you have the stripes. It goes back and forth between lake stage and estuarine stage. It must have been driven by sea-level change. And then what happens is that as the strait gets wider, eventually it gets wide enough for the Earth's rotation to influence the flow, and you can get water on one side of the strait flowing in, and on the other side going out. That is when you get a much bigger flush into the Arctic Ocean." said Jakobsson.

　　This circular flow, fueled by the Coriolis effect, impeded the Atlantic waters to further slide under the Arctic waters: they entered the surface in the strait and oxygenated before getting down to bottom. This turned the sediments gray, due to oxygenation and the first marine fossils emerged.

　　The last, brownish silt is abundant in iron and manganese oxides, denoting high oxygen amounts and full of marine fossils.

　　所考词汇：

　　1. in retrospect=think in reconsideration

　　2. velocity=speed

　　3. intense= extreme

　　4. scenario= a version of events

　　更多托福阅读考试信息

　　了解环球教育托福课程