1. Mantle Convection:
* The Earth's mantle is constantly in motion due to convection currents. Hotter, less dense material rises, while cooler, denser material sinks.
* This convection is driven by heat from the Earth's core.
2. Seafloor Spreading:
* At mid-ocean ridges, the rising mantle material reaches the surface, creating a divergent plate boundary where the plates are moving apart.
* This separation creates space for the rising mantle to be exposed.
3. Decompression Melting:
* As the mantle rock rises, it experiences a decrease in pressure (decompression).
* The pressure reduction lowers the melting point of the rock.
* This is similar to how water boils at a lower temperature at higher altitudes (lower pressure).
* The rock, now at a temperature above its new melting point, begins to melt, producing magma.
4. Magma Production:
* The magma produced by decompression melting is typically basaltic, which is rich in iron and magnesium.
* This magma rises to the surface, erupts as lava, and cools to form new oceanic crust.
In summary: Decompression melting is a key process in seafloor spreading, responsible for the creation of new oceanic crust. The decrease in pressure as mantle rock rises causes it to melt, producing the magma that forms the foundation of the ocean floor.
