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：甲烷和PETM

　　内容回忆：

　　总共 4 段，

　　第 1 段提出在 PETM 时期，地球的气温急剧上升，这个温度上升可能和 carbon 的释放有关，而那个时候 carbon 可能是以 methane 的形式被释放进入了大气和海洋系统

　　第 2 段讲到 methane 是由于有机物的分解产生的，如果陆地分解会进入大气，如果再海底分解，会进入海洋，且海底会有一种叫做 methane hydrate 的类似于冰的固体物质

　　第 3 段讲到 methane hydrate 需要特殊的气温和气压才能稳定存在，解释了一下具体的他的生存环境，当时有没有这么多量的 methane hydrate 还不确定，还有一个问题是发生了什么可以使得这么多的 methane hydrate 释放出来。第 4 段讲 methane hydrate 释放出来可能有两个原因，第一个是深海的水温上升，第二个是由于大陆架的边缘发生了 landslides.

　　参考阅读：TPO5-3:The Origin of Petroleum

　　Petroleum is defined as a gaseous, liquid, and semisolid naturally occurring substance that consists chiefly of hydrocarbons (chemical compounds of carbon and hydrogen). Petroleum is therefore a term that includes both oil and natural gas. Petroleum is nearly always found in marine sedimentary rocks. In the ocean, microscopic phytoplankton (tiny floating plants) and bacteria (simple, single-celled organisms) are the principal sources of organic matter that is trapped and buried in sediment. Most of the organic matter is buried in clay that is slowly converted to a fine-grained sedimentary rock known as shale. During this conversion, organic compounds are transformed to oil and natural gas.

　　Sampling on the continental shelves and along the base of the continental slopes has shown that fine muds beneath the seafloor contain up to 8 percent organic matter. Two additional kinds of evidence support the hypothesis that petroleum is a product of the decomposition of organic matter: oil possesses optical properties known only in hydrocarbons derived from organic matter, and oil contains nitrogen and certain compounds believed to originate only in living matter. A complex sequence of chemical reactions is involved in converting the original solid organic matter to oil and gas, and additional chemical changes may occur in the oil and gas even after they have formed.

　　It is now well established that petroleum migrates through aquifers and can become trapped in reservoirs. Petroleum migration is analogous to groundwater migration. When oil and gas are squeezed out of the shale in which they originated and enter a body of sandstone or limestone somewhere above, they migrate readily because sandstones (consisting of quartz grains) and limestones (consisting of carbonate minerals) are much more permeable than any shale. The force of molecular attraction between oil and quartz or carbonate minerals is weaker than that between water and quartz or carbonate minerals. Hence, because oil and water do not mix, water remains fastened to the quartz or carbonate grains, while oil occupies the central parts of the larger openings in the porous sandstone or limestone. Because oil is lighter than water, it tends to glide upward past the carbonate- and quartz-held water. In this way, oil becomes segregated from the water; when it encounters a trap, it can form a pool.

　　Most of the petroleum that forms in sediments does not find a suitable trap and eventually makes its way, along with groundwater, to the surface of the sea. It is estimated that no more than 0.1 percent of all the organic matter originally buried in a sediment is eventually trapped in an oil pool. It is not surprising, therefore, that the highest ratio of oil and gas pools to volume of sediment is found in rock no older than 2.5 million years - young enough so that little of the petroleum has leaked away - and that nearly 60 percent of all oil and gas discovered so far has been found in strata that formed in the last 65 million years This does not mean that older rocks produced less petroleum; it simply means that oil in older rocks has had a longer time in which to leak away.

　　How much oil is there in the world? This is an extremely controversial question. Many billions of barrels of oil have already been pumped out of the ground. A lot of additional oil has been located by drilling but is still waiting to be pumped out. Possibly a great deal more oil remains to be found by drilling. Unlike coal, the volume of which can be accurately estimated, the volume of undiscovered oil can only be guessed at. Guesses involve the use of accumulated experience from a century of drilling. Knowing how much oil has been found in an intensively drilled area, such as eastern Texas, experts make estimates of probable volumes in other regions where rock types and structures are similar to those in eastern Texas. Using this approach and considering all the sedimentary basins of the world, experts estimate that somewhere between 1,500 and 3,000 billion barrels of oil will eventually be discovered.

　　更多托福阅读考试信息

　　了解环球教育托福课程