2019年8月10日托福阅读真题+题目+答案：Formation of Earth’s Atmosphere and Oceans

2019年8月10日托福阅读真题+题目+答案：Formation of Earth’s Atmosphere and Oceans

Early in its history, Earth was molten and had neither atmosphere nor oceans. █However, as the gradually cooling surface began to solidify into rock, intense heat trapped below Earth’s outer crust had to get out somehow. █The result was surely volcanoes, geysers, earthquakes, and a variety of other geological events that literally blew off steam and pent-up heat through cracks in the surface.█ “Outgassing” of this sort happens even today, though at only a few locations on Earth and rather infrequently at that. █But several billion years ago, this type of geological activity was surely more widespread and frequent.Scrutiny of modern volcanoes shows that lots of steamy water vapor, carbon dioxide, and nitrogen would have then undoubtedly emerged, along with vast quantities of ash and dust. Smaller amounts of hydrogen, oxygen, and other gases doubtless accompanied these early planetary eruptions. Calculations imply that over the course of Earth’s history, enough gas was exhaled through fissures from Earth’s interior to create much of our current atmosphere. The rest presumably came from comets and meteorites that could have scattered large quantities of matter on young Earth. Even today, some 40 thousand tons of extraterrestrial matter falls to Earth each year, almost all of it burning in the air or splashing in the ocean.

The origin of our present atmosphere is therefore a combination of terrestrial outgassing and interplanetary assault (further changed by later biological events). In truth, Earth's atmosphere is perhaps still adjusting, as present-day volcanoes occasionally sputter gas and heat amid incoming debris arriving from space. Today’s atmosphere was not, however, derived directly from a mixture of interstellar gases. The composition of Earth's atmosphere thus differs considerably from the average cosmic abundance of the elements.

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1.The word ‘Scrutiny” in the passage is closest in meaning to

A basic knowledge

B frequent comparison

C powerful eruption

D close observation

2.The word 'undoubtedly' in the passage is closest in meaning to

A certainly

B slowly

C forcefully

D predictably

3.According to paragraph 1，all of the following are true of outgassing EXCEPT:

A It involves volcanoes, geysers: earthquakes, and other geological activities.

B Today it can take place at any location on Earth's surface.

C The gases that emerged as a result of it billions of years ago included some hydrogen and oxygen.

D It occurred more frequently in the past than it does today.

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