Magma generation Decompression melting of asthenospheric rock creeping towards the surface is the most important source of magma on Earth. Most of this erupts at mid-ocean ridges to form the distinctive mid-ocean ridge basalt (MORB) of the ocean crust. Magmas are also generated by decompressional melting of the asthenosphere above subduction zones and in areas of continental rifting.
magma generation decompression melting of asthenospheric rock creeping towards the surface is the most important source of magma on earth most of this erupts at mid-ocean ridges to form the distinctive mid-ocean ridge basalt (morb) of the ocean crust magmas are also generated by decompressional melting of the asthenosphere above subduction zones and in areas of continental rifting