What is the source of lava of volcano? From magma below crust? Or from molten crust by rubbing?
Ok, it looks like a very simple question but I still have some point want to clarify... Most images explain volcanos contain some orange stuffs as magma below volcanoes as magma chamber, but the problem is, what is the primary source of the magma? I have 2 assumptions but don't know which is correct: 1. Magma is directly supplied from magma below crust, in subduction zone the crust rubs and some cracks formed, magma rushes out from mantle and then to the surface of Earth via cracks. 2. The magma is formed by molten crust cause by rubbing and then heating, then it rushes out via cracks. In other words, the magma is originally a part of crust and it just melt again through rubbing, which is not related to the magma below crust. Which is correct?