Magmatism.pptx

Magmatism is the activity or the motion of the magma. Rocks that are subjected to high temperature and pressure melt and become the magma.

1. MAGMATISM

2. Magmatism is the activity or the motion of the magma. Rocks that are subjected to high temperature and pressure melt and become the magma. Magma is a semi-liquid molten rock mixture that can be found in the lower portion of the crust and the upper part of the mantle.

3. Types of Magma Generation A. Subduction The geodynamic process of one plate sliding beneath another which occurs along deep-sea trenches

4. B. Hot-spot Volcanism A "hot spot" represents a region of volcanism above a relatively stationary region of intense heat within the Earth's mantle, a so-called mantle plume.

5. C. Magmatism along rift zones The less spectacular formation of mountains, involving magma addition into the Earth’s surface, occurs along with incipient spreading centers, oceanic ridges, and (continental) rifts .

6. Special conditions required for the formation of magma ( Marshak , et al, Essentials of Geology, 2013): a. Crust and mantle are almost entirely solid, indicating that magma only forms in special places where pre-existing solid rocks undergo melting. b. Melting due to decrease in pressure ( decompression melting ): The decrease in pressure affecting a hot mantle rock at a constant temperature permits melting forming magma. This process of hot mantle rock rising to shallower depths in the Earth occurs in mantle plumes, beneath rifts and beneath mid- ocean ridges.

7. c. Melting as a result of the addition of volatiles ( flux melting ): When volatiles mix with hot, dry rock, the volatile decreases the rock’s melting point and they help break the chemical bonds in the rock to allow melting. d. Melting resulting from heat transfer from rising magma ( heat transfer melting ): A rising magma from the mantle brings heat with it that can melt the surrounding rocks at the shallower depths.

8. Table 3. Summary of the conditions for magma generation and the areas it occurs