Earth Science: Geology, Geomorphology & Tectonics

Posted on Nov 29, 2024 in Geology

Earth Science Fundamentals

Key Disciplines

  • Geomorphology: The study of landforms and surface processes (geo – earth; morph – form).
  • Physiography: The study of land and sea distribution and relief formation.
  • Geology: The study of Earth’s structure, composition, and materials (minerals and rocks).
  • Soil Science (Pedology): The study and classification of soils and soil horizons (0-305 meters).
  • Climatology: The study of climate.

Earth’s Internal Structure

  • Core: Earth’s center, composed primarily of iron; inner core (solid, 4000°C) and outer core (liquid).
  • Mantle (Mesosphere): A layer of siliceous materials (2000-3200°C) surrounding the core; includes the asthenosphere (slow circular movements) and lithosphere (outer layer).
  • Crust: The rocky outer layer (5 km thick) composed of crystalline rocks.

Earth’s age is approximately 4.5 billion years.

Plate Tectonics and Related Theories

  • Isostasy: The balance between different sections of the lithosphere, influencing continental origins.
  • Continental Drift Theory (Alfred Wegener): Proposed the existence of the supercontinent Pangaea, which split into Gondwana (Southern Hemisphere) and Laurasia (Northern Hemisphere).
  • Seafloor Spreading Theory (1960s): Volcanic activity at mid-ocean ridges creates new oceanic crust, causing the seafloor to spread.
  • Plate Tectonics Theory: Earth’s crust is fractured into plates that move due to mantle convection. Studies using GPS track plate movements.
  • Convective Cell Theory: Mantle convection, driven by heat from the core, causes magma to rise and displace plates.

Plate Boundaries

  • Divergent (Abduction): Plate separation zones, often at mid-ocean ridges, where magma rises.
  • Convergent (Subduction): Plates collide, one sinking beneath the other; zones of high seismic and volcanic activity.
  • Transform (Fault): Plates slide past each other, generating significant seismic activity.

Rock Classification

  • Igneous Rocks: Formed from cooled magma; extrusive (volcanic, rapid cooling) and intrusive (formed within the crust, slow cooling).
  • Sedimentary Rocks: Formed from the accumulation and cementation of sediments.
  • Metamorphic Rocks: Formed from existing rocks transformed by heat and pressure.

Relief and Diastrophism

Earth’s surface undergoes constant transformation due to endogenous (internal) and exogenous (external) forces.

Endogenous Forces

  • Earthquakes: Sudden movements of Earth’s crust, originating at the hypocenter and felt at the epicenter.
  • Orogeny: Vertical movements forming mountains and landforms.
  • Volcanism: The eruption of molten rock (magma and lava) from the Earth’s interior.

Exogenous Forces (Erosive Agents)

These forces tend to level the Earth’s surface.

  • Temperature: Causes rock fragmentation through expansion and contraction.
  • Wind: Erodes and transports materials, forming dunes.
  • Sea: Causes erosion and sedimentation, modifying coastlines.
  • Rivers: Create valleys and canyons through erosion.
  • Rain: Erodes and transports materials, especially in areas lacking vegetation.

Orogenetic Movements

Vertical movements creating new reliefs.

  • Folding: Lateral forces cause flexible rocks to fold (anticlines and synclines).
  • Faulting: Vertical forces create uplifted (horsts) and down-dropped (grabens) areas.