* Compositional differences: Oceanic crust is primarily composed of basalt, a rock rich in magnesium and iron (mafic). This composition has a lower melting point than the more silica-rich (felsic) rocks that make up the continental crust.

* Pressure differences: Oceanic crust is thinner than continental crust, meaning the pressure exerted on the mantle below is lower. This lower pressure decreases the melting point of the mantle rock.

In summary:

* Oceanic ridges: The mantle beneath the oceanic crust is already hot enough to melt due to its lower melting point and the reduced pressure.

* Continental crust: The continental crust, being thicker and composed of higher melting point rocks, requires even higher temperatures for the mantle to melt and generate magma.

Therefore, the lower melting point of the mantle rocks and reduced pressure in the oceanic setting make magma formation possible at lower temperatures compared to the continental setting.