Volcanoes can be formed by plumes of magma originating in this layer of the Earth below the crust
The shell within the earth, some tens of kilometers below the surface and 
of ... A swelling of the crust of a lava flow formed by the puffing-up of gas or vapor
... [DOC] [TLE] plate tectonics | geology | Britannica.com [PAR] Dec 2, 2015 ... A cross section of Earth's outer layers, from the crust through the lower mantle.