What role does magma play in helping heat escape Earth?
You can skip this. • What special conditions are required to make magma? –For us, we can roughly divide up magma into two groups: 1) Magma formed in the mantle. This magma is more mafic. The book calls this gabbroic magma. This magma forms rocks like basalt and gabbro. 2) Magma formed in the crust. This magma is more felsic. The book calls this granitic magma. This magma forms rocks like granite and rhyolite. –This part of the section describes how gabbroic magma forms. However, it is not very complete. Here are the major ways that gabbroic magma forms: | 1) pressure-release melting. This is shown in Figure 4.4 (not very well). The text states that rock moves upward by convection. The rock is hot, but very solid. The surrounding pressure is great enough that it cannot melt (melted rock requires more space than solid rock–so, the pressure doesn’t allow the rock to melt). However, as the rock moves toward the surface, the pressure on it decreases. It can happen that the pressure on th
