托福阅读真题+题目+答案：Earth's Early History

托福阅读真题+题目+答案：Earth's Early History

Earth's history began about five billion years ago with the formation of the solar system out of a massive cloud of dust and gas called the solar nebula. The particles making up the solar nebula gravitated toward one another, and the cloud collapsed spinning rapidly and flattening to form a disk. As gravitational collapse continued and inward pressure increased. the material near the center of the disk became denser and hotter. Eventually, the temperature became so great that the nuclei of colliding atoms (largely hydrogen and some helium)fused, and thermonuclear reactions were ignited the sun was born as a star

1.According to paragraph 1, the Sun became a star at the point in its evolution when

A.the solar nebula collapsed and began spinning rapidly

B.the particles making up the solar nebula began to gravitate toward the center

C.thermonuclear reactions began

D.the cloud of dust and gas flattened to become a disk

Not all the material in the solar nebula drifted toward the center While the Sun was still forming, dust particles and gases at some distance from the center began to collide and stick together and eventually formed planets bound in orbits around the Sun. One of these planets was Earth. The history of Earth's first billion years- the Hadean eon-can only be inferred from the models of astronomers and from studies of the moon and meteorites. The planet suffered so much bombardment by other objects in the solar system and so much movement of material on its surface that no intact sample of rock survived the cataclysmic, primordial(early Earth) events.

2.The word “drifted” in the passage is closest in meaning to

A.collapsed

B.was located

C.ended up

D.moved gradually

3.Which of the following can be inferred from paragraph 2 about Earth’s rocks during the Hadean eon?

A.They were younger than rocks on the Moon

B.They had not yet come together to form a planet

C.They formed from material in the solar nebula that drifted toward the center

D.They were very different from the rocks that make up earth today

As the newly formed Earth grew, it began to heat up. Enormous amounts of heat must have been released as the inner parts of the growing mass were compressed by the accumulation of the outer layers. Meteorites and other planetary debris released additional eat as they hit with sufficient impact to form huge craters. But probably the most significant source of heat on the new planet came then, as it still does, from the decay of radioactive elements (uranium, thorium and potassium)in its interior

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