【英语时差8，16】夏威夷的下一个火山

 Look at a map of Hawaii and you'll see volcanic¹ islands strung out like pearls on a necklace. The biggest--and the youngest--is Hawaii, in the south-east corner. As the islands stretch away to the north-west they become older and more worn. While Hawaii is about a million years old, the extinct volcano of Kauai on the north-west end is five times older.   The Hawaiian islands were formed by what geologists² call "hot spot" volcanos. These occur where hot magma from the Earth's liquid mantle³ is steadily⁴ 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 uneven⁵ 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 north-west Kauai is old and extinct, while the volcanos on Hawaii's south-east edge are the most active in the world.

The Hawaiian hot spot is now located about seventeen miles off the south-east coast of Hawaii. There's no new island there, but there is a huge, underwater volcano, rising almost three miles above the ocean floor. This new volcano will break the ocean's surface in about fifty thousand years, giving us our next Hawaiian island. 

1 volcanic   

adj.火山的；象火山的；由火山引起的

参考例句：

• There have been several volcanic eruptions this year.今年火山爆发了好几次。
• Volcanic activity has created thermal springs and boiling mud pools.火山活动产生了温泉和沸腾的泥浆池。

2 geologists   

地质学家，地质学者( geologist的名词复数 )

参考例句：

• Geologists uncovered the hidden riches. 地质学家发现了地下的宝藏。
• Geologists study the structure of the rocks. 地质学家研究岩石结构。

3 mantle   

n.斗篷，覆罩之物，罩子；v.罩住，覆盖，脸红

参考例句：

• The earth had donned her mantle of brightest green.大地披上了苍翠欲滴的绿色斗篷。
• The mountain was covered with a mantle of snow.山上覆盖着一层雪。

4 steadily   

adv.稳定地；不变地；持续地

参考例句：

• The scope of man's use of natural resources will steadily grow.人类利用自然资源的广度将日益扩大。
• Our educational reform was steadily led onto the correct path.我们的教学改革慢慢上轨道了。

5 uneven   

adj.不平坦的，不规则的，不均匀的

参考例句：

• The sidewalk is very uneven—be careful where you walk.这人行道凹凸不平—走路时请小心。
• The country was noted for its uneven distribution of land resources.这个国家以土地资源分布不均匀出名。