Deformation of Earth Crust.pptx

Deformation of the Crust

• The deformation of the Earth's crust occurs due to various geological processes, primarily influenced by tectonic plate movements.

Continental Drift Theory

• The continental drift theory, proposed by Alfred Wegener in 1912, suggests that continents shift positions on their tectonic plates, moving over time across the Earth's surface. This theory was initially rejected because Wegener could not adequately explain the mechanism driving this movement.

• Evidence supporting this theory includes the presence of similar fossilized plants and animals, as well as comparable geological structures found on different continents, underscoring a historical connection between these landmasses.

Seafloor Spreading

• Seafloor spreading is a geological process where new oceanic crust is formed through volcanic activity at mid-ocean ridges, while older crust is pushed away from the ridge.

• Proposed by geophysicist Harry H. Hess in 1960, this theory highlights the conveyor belt function of ocean floors, where new crust wells up, and the oceanic crust sinks into deep trenches at continental edges. This process contributes to plate tectonics.

Tectonic Plates

Structure of Tectonic Plates

• Tectonic plates are large, rigid slabs of solid rock that cover Earth's surface.

• These plates vary in size, comprised of seven primary plates, seven secondary plates, and over sixty tertiary plates.

Major Plates

• Major tectonic plates with an area greater than 20 million km² include:

  • Pacific Plate: 103,300,000 km²

  • North American Plate: 75,900,000 km²

  • Eurasian Plate: 67,800,000 km²

  • African Plate: 61,300,000 km²

  • Antarctic Plate: 60,900,000 km²

  • Indo-Australian Plate: 58,900,000 km² (considered as two plates: Australian and Indian).

  • South American Plate: 43,600,000 km².

Minor and Micro Plates

• Minor plates (less than 20 million km² but greater than 1 million km²) include:

  • Somali Plate: 16,700,000 km²

  • Nazca Plate: 15,600,000 km²

  • Philippine Plate: 5,500,000 km²

  • Arabian Plate: 5,000,000 km²

• Microplates (less than 1 million km²) are often associated with larger plates.

Plate Boundaries

Types of Boundaries

• The movement of tectonic plates creates various boundaries:

  • Convergent Boundaries: Plates push toward each other, leading to subduction, mountain building, and earthquakes.

  • Divergent Boundaries: Plates move apart, leading to rift zones and basaltic volcanism.

  • Transform Fault Boundaries: Plates slide past one another, leading to shearing and faulting.

Effects of Plate Movement

• Plate tectonics lead to significant geological formations, including folds, faults, trenches, volcanoes, rift valleys, and mountain ranges, constantly reshaping Earth's landscape.

• For example, the Andes Mountain Range formed due to the subduction of the Nazca plate under the South American plate.

Features of the Ocean Floor

• The ocean floor is defined by various geological features:

  • Abyssal Plains: Flat expanses of the deep sea floor.

  • Mid-Ocean Ridges: Underwater mountain ranges formed at divergent boundaries.

  • Seamounts: Submarine volcanoes that may create islands.

  • Trenches: Deep underwater valleys formed at convergent boundaries, where one plate subducts under another.

  • Hydrothermal Vents: Sites where heated water and minerals are released from the ocean floor.

Evolution of Ocean Basins

• Ocean basins have been modifying for billions of years due to plate tectonics, leading to the current positioning of continents and ocean floors.

• The breakup of the supercontinent Pangea initiated significant changes in ocean basin growth, affecting sea levels and sedimentation patterns.

Predictions of Future Tectonic Movements

• Understanding the dynamics of plate tectonics enables predictions about Earth's future landscape. As tectonic plates continue to shift, they will further reshape continents, potentially leading to new mountain ranges and oceanic features.