Exogenic Processes in Geology

Exogenic Processes

• Processes at Earth's surface influenced by external forces
• Includes weathering, erosion, mass wasting, and deposition

Weathering

• Disintegration (physical) and decomposition (chemical) of rocks
• Breaks down rocks into smaller particles (sand, gravel)
• Types:
  • Physical/Mechanical: Breakdown without composition change; size/shape of rocks alters due to factors like ice wedging, pressure release, abrasion, and exfoliation.
  • Chemical: Rocks weaken and disintegrate through reactions (dissolution, hydrolysis, oxidation); alters mineral compositions.
  • Biological: Living organisms (insects, tree roots) contribute to disintegration; produce acids that can dissolve rocks.
  • Processes/factors that bring about biological weathering:
    • Root wedging
    • Burrowing of animals
    • Anthropogenic activities

Erosion

• Separation and removal of weathered rocks by agents (water, wind, glaciers)
• Transports materials to depositional areas
• Mass wasting: Movement of sediments downslope due to gravity (falls, slides, avalanches, flows)

Deposition

• Weathered materials carried by erosion settle in a specific location
• Geological process

Earth's Internal Heat

• Heat energy results from atom/molecule movement in solids/liquids/gases.
• Crucial for Earth's habitability.
• Sources:
  • Primordial heat: Heat accumulated during Earth's formation.
  • Radiogenic heat: Heat from radioactive decay (uranium, thorium, potassium).
• Heat Transfer:
  • Conduction: Heat transfer between particles in direct contact (occurs in solid Earth's upper layers).
  • Convection: Heat transfer via fluid movement (occurs in molten rock zones).
  • Radiation: Heat transfer through electromagnetic waves (between Sun and Earth).
• Subduction: One tectonic plate slides beneath another.
• Methods of heat transfer also include conduction, convection, radiation

Endogenic Processes

• Geological processes occurring below Earth's surface
• Includes tectonic movements, metamorphism, seismic activity, and magmatism

Magma

• Molten rock beneath Earth's surface (specifically in the mantle)
• Magmatism: Formation and movement of magma
• Substances/Elements present:
  • Oxygen, Silicon, Aluminum, Iron, Calcium, Sodium, Potassium, Magnesium, etc.
  • Various percentages in magma composition.
• Formation:
  • Partial melting of minerals in the lower crust/upper mantle at different temperatures and pressures. This may involve increase in temperature, decrease in pressure, or addition of volatiles (fluids like water, gases).

Intrusion/Extrustion

• Intrusion: Magma forces its way into surrounding rocks without erupting.
• Extrusion: Magma erupts onto the Earth's surface as lava

Volcanism

• Volcanism: Broad term encompassing geological phenomena like volcanic eruptions and hot springs.
• Processes create volcanic landforms (volcanoes) and volcanic rocks.

Rock Behaviors Under Stress

• Tensional Stress: Pulling forces, causing lengthening and breaking. Common in divergent plate boundaries
• Compressional Stress: Squeezing forces, causing folding or fracturing. Common in convergent plate boundaries
• Shear Stress: Forces sliding in opposite directions resulting in slippage. Found in transform plate boundaries
• Geologic Structures:
  • Folds: Bending of rocks due to compressive stresses (monocline, anticline, syncline).
  • Faults: Fractures in rocks caused by stress (hanging wall and footwall).

Seafloor Spreading

• Seafloor continuously spreads at mid-ocean ridges, pushing older crust away and creating new oceanic crust.
• Three lines of evidence for seafloor spreading:
  • Molten materials
  • Magnetic stripes
  • Drilling core samples

Ocean Basins

• Features: continental shelf, slope, rise, abyssal plain, ridges, trenches, islands
• Formation: Shaped by plate tectonics.

Stratified Rocks

• Form from layers of deposited sediments or volcanic products
• Stratigraphy: The study of rock layers, including their description, correlation, and interpretation.

Relative Age Dating

• Determining the age of rocks relative to each other using various principles, including:
  • Law of Superposition: Older layers are below younger layers.
  • Law of Original Horizontality: Layers are deposited horizontally.
  • Law of Cross-Cutting Relationships: A feature that cuts across rocks is younger than the rocks it cuts.
  • Law of Lateral Continuity: Layers are initially continuous unless interrupted by erosion.
  • Law of Inclusions: An inclusion (piece of one rock within another) is older than the rock it is within.
• Methods for correlating rocks: rock type, index fossils, stratigraphy, detailed characteristics

Absolute Age Dating

• Determining the specific numerical age of rocks using various methods, including:
  • Radiometric dating: Measures radioactive decay.
  • Amino acid dating: Measures changes in amino acid compositions.
  • Dendrochronology: Measures tree ring patterns.
  • Thermoluminescence: Measures light absorbed.
  • Fluorine dating: Measures fluorine content in fossils/bones.

Geologic Time Scale

• A standard timeline for Earth's history.
• Divided into eons, eras, periods, and epochs.

Eras

• Paleozoic (early life)
• Mesozoic (age of dinosaurs)
• Cenozoic (age of mammals)

Explore the various exogenic processes that shape the Earth's surface. This quiz covers weathering types, erosion mechanisms, and the impact of biological factors. Test your understanding of these crucial geological processes.