Why does melting occur at divergent plate boundaries

Explanation:

As plates move apart at the divergent plate boundary the release of pressure produces partial melting of the underlying mantle. This molten material, known as magma, is basaltic in composition and is buoyant. As a result, it wells up from below and cools close to the surface to generate new crust

At divergent plate boundaries hot mantle rock rises into the space where the plates are moving apart. The rock is under lower pressure; this lowers the melting temperature of the rock and so it melts.