托福阅读考试涉及历史，政治，科技，生物等等，非常广泛的话题，在托福阅读考试紧张的时间里，如果对文章背景不熟悉，轻则影响考生心情重则影响理解和考分，本篇为大家带来的新托福阅读背景材料是LAVA。
Lava is magma that breaks the surface and erupts from a volcano. If the magma is very fluid, it flows rapidly down the volcano’s slopes. Lava that is more sticky and less fluid moves slower. Lava flows that have a continuous, smooth, ropy, or billowy surface are called pahoehoe (pronounced pah HOH ee hoh ee) flows; while a a (pronounced ah ah) flows have a jagged surface composed of loose, irregularly shaped lava chunks. Once cooled, pahoehoe forms smooth rocks, while a a forms jagged rocks. The words pahoehoe and a a are Hawaiian terms that describe the texture of the lava. Lava may also be described in terms of its composition and the type of rock it forms. Basalt, andesite, dacite, and rhyolite are all different kinds of rock that form from lava. Each type of rock, and the lava from which it forms, contains a different amount of the compound silicon dioxide. Basaltic lava has the least amount of silicon dioxide, andesitic and dacitic lava have medium levels of silicon dioxide, while rhyolitic lava has the most.
以上就是前程百利为大家整理的托福阅读材料，希望能够帮助大家进行托福备考。若您想了解托福考试更多相关信息请关注前程百利。
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