L2.2.1: Magma Formation

• ● Magma

  ○ It is composed of molten or semi-molten rock, volatiles, and solids (and sometimes crystals) that are found beneath the surface of the Earth.

  ○ Magmas are formed under certain circumstances. They are formed when conditions are right to cause preexisting solid rocks to melt.
• Magma Formation

  ● Decompression Melting

  ● Flux Melting

  ● Heat Transfer Melting
• ● Decompression Melting

  ○ Melting due to a decrease in pressure. 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.

  ○ Closer to crust = less pressure.

  ○ Kapag mataas yung pressure kaya imaintain yung chemical bonds ng mga atom and restrict the material from melting.
• ● Flux Melting

  ○ Melting as a result of the addition of volatiles. Flux melting occurs when water vapor or carbon dioxide is added to rock. These compounds cause the rock to melt at lower temperatures. This creates magma in places where it originally maintained a solid structure. Subducting zones only!

  ○ Volatiles: gases that weaken or break down the chemical bonds between atoms.

  ○ Denser oceanic crust subducts when converging with continental crust. The oceanic crust is rich in water vapor and carbon dioxide which may affect solid rocks.
• ● Heat Transfer Melting

  ○ Rising magma from the mantle brings the heat with it and transfers it to their surrounding rocks at shallower depths which may melt.
• Places Where Magma Can Form 53:59

  ● Mid-oceanic Ridges

  ○ Decompression melting and heat transfer.

  ● Mantle Plumes (Hot Spots)

  ○ Decompression melting and heat transfer.

  ● Subduction Zone

  ○ Flux melting and heat transfer.