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    本题由lindy提供
876次学习

First identified in 1969, komatiites are Earth’s oldest known volcanic rocks and contain three times as much magnesium as do

most volcanic rocks. This chemical composition suggests that komatiites formed from the hottest lava known ever to have erupted: a high concentration of magnesium changes the physical properties of lava so that unusually high temperatures would be required for the lava to exist as a liquid.

Komatiites’ discovery was surprising in light of then-current geological theories about magmas, molten rock that forms in the Earth’s mantle (the layer beneath the crust) and composes volcanic lava eruptions. Prior to 1960, geologists Bowen and Hess disagreed over whether or not the very high temperatures needed to produce magmas rich in magnesium could have existed on Earth. Hess suggested that the presence of water, probably released from minerals decomposing in the Earth’s mantle, might have meant that a high-magnesium magma could have existed at a lower temperature. But Bowen showed experimentally that the high temperatures were indeed necessary. By 1960, it was generally accepted that volcanic rocks with such high levels of magnesium could not exist, and thus the discovery of komatiites changed geologists’ assumptions about the characteristics of the Earth’s mantle around the time of the formation of komatiites, between 2.5 and 4 billion years ago.

Which of the following most accurately describes the organization of

the passage?


    A. Two divergent views of a scientific phenomenon are reconciled.

    B. A phenomenon is described and its scientific significance is discussed.

    C. The discovery of a scientific phenomenon is traced and its implications for further research are suggested.

    D. A long-standing scientific theory is examined and recently discovered evidence is shown to support it.

    E. The ways in which a particular geological phenomenon is exceptional are detailed and classified.


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答案:
B
整篇文章是
一个现象,发现了一个东西,然后这个东西的历史性意思 选项A views are reconciled观点调节,调和,与文章结构不符 选项B 描述了一个现象,一个火山岩的M含量特高,这个现象的意义,正确 选项C implications for further research are suggested.与文章结构不符 选项D 并不是提出一个理论,再找出一些证据support的文章结构 选项E 并不是去detail 和classify这个现象的怎么不同的结构

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