at what two types of boundaries does subduction happen
Plate subduction occurs when two tectonic plates converge and at least one of them is an oceanic plate. Oceanic plates are formed at divergent plate boundaries from dense basaltic magma. This magma originates from the mantle beneath and fills the gap between the spreading plates.
Plate subduction occurs when two tectonic plates meet at a convergent plate boundary (the plates are crashing into one another) and at least one of the plates is denser than the underlying mantle. If neither plate is denser than the underlying mantle the plates will create a non-volcanic mountain range like the Himalaya.