The Earth's mantle is very important. It is important for the Earth's crust evolution, as well as being the provider of thermal and mechanical forces for plate tectonics. The mantle is what covers the most part of Earth inside if it is not there, then the heat of the core will burn the Earth's crust. And the mantle does make up 84% of Earth's volume, so that wouldn't be good!
By looking at the four graphs given and the rock layers have not been overturned. The youngest rock layer out of the four is going to be the third graph. The correct answer is the conglomerate in outcrop 3.
