Explain how volcanoes are formed at constructive and destructive plate boundaries

When the plates move the flaps hit each other and over time it will form a volcano:)

Magma forms by partial melting of upper mantle and crust. partial melt means that only a fraction of the available material forms a melt, and that the remainder stays solid. the partial melt rises because of its lower density and ascends through he crust. this is so conclusive mean the answer would be magma igneous rocks or balistic magma.