9. Volcanoes and earthquakes occur at plate boundaries because plate boundaries are areas where plates are constantly moving and interacting with each other. Volcanoes occur at convergent boundaries because the subduction of one plate beneath another creates conditions that can cause the melting of rock and the formation of magma. Earthquakes occur at both convergent and divergent boundaries because the movement and interactions of plates can create intense pressure and stress that eventually gets released in the form of seismic activity.
10. Convergent boundaries have more metamorphic rocks because the collision and subduction of plates at these boundaries causes intense heat and pressure, which can metamorphose existing rocks into new forms. Divergent boundaries, on the other hand, have more igneous rocks because the separation of plates at these boundaries allows for the upwelling of magma from the mantle, which eventually solidifies to form igneous rocks.