mantle

definition: 
The region of the earth’s interior between the crust and the core, believed to consist of hot, dense silicate rocks (mainly peridotite)
sentence: 
Hot new ocean crust forms at mid-ocean ridges, cools, and sinks back into the mantle, shedding heat and driving the plates.
difficulty: 
easy
toefl frequency: 
2
toefl classification: