Exactly what drives plate tectonics is not known. One theory is that convection within the ... takes place at four types of boundaries: divergent boundaries, where new crust is formed; convergent ...

The Earth is made up of different layers: Therefore, instead of tectonic plates moving because of the convection currents ... is called the theory of plate tectonics.

This is called a constructive or divergent plate boundary. These are usually found under oceans. As the plate moves apart, magma rises to the surface and cools, forming shallow-sided volcanoes.