Week 4 Topic: Geologic Processes on Earth

Geologic Process

  • šExogenous process – occur on or near the surface of Earth. They are usually influenced or driven by gravity, water, wind and organisms. These could be destructive occurrences that leave significant changes on the landscape and even in the ecosystem of an area.
  • šEndogenous Process – take place within or in the interior of Earth. The driving force is the thermal energy of the mantle. Most of the thermal energy originates from the decay and disintegration of radioactive elements in Earth’s core.

Exogenous Process

  • Erosion – šIt is the process by which Earth’s surface is worn away by wind, water, or ice. The process of erosion moves rock debris or soil from one place to another. Erosion takes place when there is rainfall, surface runoff, flowing rivers, seawater intrusion, flooding, freezing and thawing, hurricanes, wind, etc. These are forces of nature, whether violent or passive, capable of exfoliating and scraping Earth’s surface and exfoliating and scraping Earth’s surface and exposing the layers underlying it.
  • šWeathering – it is the disintegration of rocks, soil, and minerals together with other materials through contact with Earth’s subsystems. Weathering happens even without movement or transportation. The breaking down of soil and rocks happen in situ or on the spot.
    • šPhysical Weathering – is the breakdown of rocks by mechanical forces concentrated along rocks fractures. This can occur due to changes, whether sudden or not, in temperature, pressure, etc.
    • šChemical Weathering – is the process by which rocks break down by chemical reactions. In this process, new or secondary minerals develop and sometimes replace the original properties of the minerals in the original rock or soil.
      • šOxidation and hydrolysis are chemical processes that contribute to chemical weathering. Another contributor to chemical weathering is acid rain which may cause metals or stones to corrode or deteriorate and change their properties because of the reaction to acides by some of the minerals in soul and rocks that make them up.
  • Mass Wasting – This refers to the movement of large masses of materials down a slope or steep-sided hill or mountain due to the pull of gravity. Mass wasting is very destructive in areas with increased water flow, steep slopes, scare or no vegetation, or vibrating or moving ground.
    • Debris flow – šHappens when a large amount of sediments, usually rocks of various sizes, falls down the slope. Unlike a landslide, debris flow does not need water to flow down.
    • šMudflow – šHappens when combined soil and water flow down a slope. This usually happens near rivers or streams where soil or sand is always moist or has been soaked in water for a long time. The weight of mudflow indicates the severity of risk when it flows down a community.
    • šSlump – šA slow movement of soil along a curved surface. In time, the area would look curved because of the depression formed by the sinking land.
  • Sedimentation – It is the accumulation of materials such as soil, rock fragments, and soil particles settling on the ground. This usually occurs in streams, and sea erosion. Over time, the sediment load becomes thick and forms a new layer of ground. In some small inland waters, this sediment layer will eventually dry up the water and become part of the soil. In oceans, the sediment layer can form the ocean basin.


Endogenous Process

  • šAre responsible for earthquakes, development of continents, mountain building, volcanic activities, and other movements related to Earth’s crust.
    • Magmatism – šHappens when magma is generated and develops into igneous (magmatic) rocks. The process can take place either under the surface or on the surface of Earth.
    • Volcanism (Plutonism) – šIt is the process that usually happens after magma is formed. Magma tries to escape from the source through openings such as volcanoes or existing cracks on the ground. Magma comes out with extreme heat and pressure and may cause destructive explosions. As soon it reaches the surface of Earth, it is now called lava.
    • Metamorphism – šIt is the process of changing the materials that make up a rock. The chemical components and geologic characteristics of the rock changed due to heat and pressure that are increasing or decreasing. The minerals in the rock may change due to heat and pressure that are increasing or decreasing. The minerals in the rock may change even if the rock does not melt.


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