了解托福閱讀文章的一些背景知識，對于提高托福閱讀做題準確率，拓展知識儲備都很有好處，小編為大家帶來托福閱讀背景知識，希望對大家有所幫助。
　　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.
　　以上就是今天的托福閱讀背景知識，每天熟悉一部分托福常考知識點，堅持下來，一定會有不小的進步，了解背景知識的同時不要忘記，找些相關知識的單詞造句試試，以便考試的時候能派上用場，英語不是一朝一夕的事，所以大家一定要勤加練習。