英语听力练习网：夏威夷超级火山.doc

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英语听力练习网：夏威夷超级火山

***英语听力频道为大家整理的英语听力练习网：夏威夷超级火山，供大家参考:)
Look at a map of Hawaii and you’ll se 第1页 /总页数 2 页
英语听力练习网：夏威夷超级火山

***英语听力频道为大家整理的英语听力练习网：夏威夷超级火山，供大家参考:)
Look at a map of Hawaii and you’ll see volcanic islands strung out like pearls on a necklace. The biggest–and the youngest–is Hawaii, in the southeast corner.
As the islands stretch away to the northwest they become older and more worn. While Hawaii is about a million years old, the extinctvolcano of Kauai on the northwest end is five times older.
The Hawaiian islands were formed by what geologists call “hot spot” volcanos. These occur where hot magma from the Earth’s liquid mantle is steadily forced through the Earth’s crust.
Hot spots can last for millions of years, staying in the same place while the plates of the Earth’s crust move gradually overhead.
The plates of the Earth’s crust move at uneven speeds, so when the plate moves slowly, this allows a tremendous volcano to build up. That’s why we get a string of separate volcanos, rather than a continuous line.
This is exactly what’s happened with the Hawaiian islands. The hot spot stayed in the same place, pushing up a string of volcanos as the Earth’s crust moved over it.
Because of this, the volcano on northwest Kauai is old and extinct, while the volcanos on Hawaii’s southeast edge are the most active