Endogenic Processes within the Earth

Earth’s Internal Heat

• The heat coming off the Earth comes in two forms: Primordial and Radioactive
  • Primordial Heat:
    • it is the remaining heat from accretion and bombardment of the Earth during the early stages of its creation.
    • it is said that Earth was formed from accumulation of tiny fragments of dust and gas due to gravity pulling them together
      • this is the process of accretion
    • in its early days, tiny rocks and celestial bodies that formed near the Earth’s vicinity collided into Earth due to its gravity.
      • this is the process of bombardment
    • both of these processes generate too much heat which contribute to the Earth internal heat we have today.
  • Radioactive Heat
    • it is heat coming off as a result of long-term radioactive decay.
    • as radioactive isotopes decay, they also generate heat, which contribute to the Earth’s internal heat.

Internal Temperature of the Earth

• The Earth is divided into different layers.
• Each layer seem to be hotter than the previous one.
  • Core-Mantle Boundary:
  • Inner-Outer Core Boundary:
  • Earth’s Center:

Redistribution of Earth’s Heat

• Earth’s heat is redistributed through simultaneous conduction, convection, and radiation.
  • Convection occurs only in the mantle.
  • Conduction occurs through transition zones such as in the crust or the core boundaries.

Magmatic Process

• The magmatic process concerns the conditions for formation of magma and magmatic differentiation.

Conditions for Magma Formation

• Some conditions for the formation of magma include:
  • Crust and mantle should be almost entirely solid.
    • This means that magma is only formed when pre-existing rocks melt.
  • Decrease in pressure (Decompression Melting)
    • As pressure decreases, rocks become less compact and may permit rock melting which turns into magma.
    • This often occur in geological areas such as mantle plumes and beneath rifts and mid-ocean ridges.
  • Addition of volatiles (Flux Melting)
    • Volatiles mixed with hot, dry rock decreases the rock’s melting point.
    • These help the rock break its chemical bonds and permit melting.
  • From rising magma (Heat Transfer Melting)
    • As hot magma rises from the mantle, it also heats up surrounding rock.
    • As a result, it melts these surrounding rocks into magma as it rises from the mantle.

Magmatic Differentiation

• When magma cools, it slowly changes composition.
  • This change in composition allows for the formation of different secondary magma.
  • Depending on the composition of the secondary magma, it may form different igneous rocks.
  • The process where magma forms various igneous rocks with different mineral compositions is called magmatic differentiation.
• Magmatic differentiation has three processes:
  • Crystal Fractionation (or Fractional Crystallization)
    • The composition of magma changes due to crystallization.
    • Some minerals in the magma may crystallize first and settle down.
    • This makes the magma rich in other minerals that crystallize much longer.
  • Partial Melting
    • Not all minerals melt at the same temperature.
    • Therefore, when a rock is heated, some minerals in the rock turn to magma first, further altering the rock’s composition.
  • Magma Mixing
    • When two different magma with different compositions rises up, convection currents may mix them up.
    • This would then make a magma that is intermediate of the two parent magmas.