【托福阅读题型：The Formation of Volcanic Islands句子插入题】托福阅读中句子插入题是重要题型之一。根据托福阅读题型不同来进行专项练习，是短期提高托福阅读能力的有效方法。同学们需要多加练习哦!

　　查看全部：托福阅读题型分类练习之句子插入题

　　托福阅读句子插入题：The Formation of Volcanic Islands

　　【Paragraph 3】How can volcanic activity occur so far from a plate boundary? The Hawaiian islands provide a very　instructive answer. ■Like many other island groups, they form a chain. ■The Hawaiian Islands Chain extends northwest　from the island of Hawaii. ■In the 1840s American geologist James Daly observed that the different Hawaii islands seem　to share a similar geologic evolution but are progressively more eroded, and therefore probable older, toward the　northwest. ■Then in 1963, in the early days of the development of the theory of plate tectonics. Canadian geophysicist　Tuzo Wilson realized that this age progression could result if the islands were formed on a surface plate moving over a　fixed volcanic source in the interior. Wilson suggested that the long chain of volcanoes stretching northwest from Hawaii　is simply the surface expression of a long-lived volcanic source located beneath the tectonic plate in the mantle. Today’s　most northwest island would have been the first to form. They as the plate moved slowly northwest, new volcanic islands　would have forms as the plate moved over the volcanic source. The most recent island, Hawaii, would be at the end of　the chain and is now over the volcanic source.(The Formation of Volcanic Islands)

　　Look at the four squares [■] that indicate where the following sentence could be added to the passage.

　　This pattern remained unexplained for a long time.

　　Where would the sentence best fit?

　　答案见下一页：