Question

If convection in the mantle increased how would the earths crust be affected

Answer 1

there would be more earthquakes and volcanic eruptions

Answer 2

Convection process happens when lighter material rises and heavier material sinks. The mantle of the earth itself is a solid and the outer core is liquid. When mantle convection increases, the heat of the earth's crust also increases since this is the main reason why the surface of the earth (the solid part or crust) is warm.