What causes the convection currents in the mantle?

What is an additional type of erosion found at the coast? what does it mean?

Which layer surrounds the center of the earth? a: crust b: core c: mantle

This is a 2017 topographic map of puerto rico in the united states, and i'm sorry that people there have suffered such a disaster. i want to ask, what do the yellow dots and areas represent on this graph? and the blue area and the little blue circle, and the little blue sign that looks like a signal tower, what do they stand for?