Understanding Plate Tectonics: Pangea, Continental Drift, and Plate Boundaries

Posted on Apr 5, 2025 in Geology

Understanding Plate Tectonics

The global theory of plate tectonics explains the cause of phenomena occurring in the geosphere, including mountain formation, volcanoes, and earthquakes.

Pangea and Panthalassa

Pangea was a supercontinent where all continents were united. The unique ocean surrounding it was called Panthalassa.

Theory of Continental Drift

Alfred Wegener developed the theory of continental drift based on cartographic, geographical, and paleontological data. This theory posits that continents were once united in a single landmass, Pangea, and subsequently drifted apart, forming the oceans.

Seafloor Spreading

Studies of the seabed in the 1960s, enabled by new technology, revealed a consistent topographic profile across all oceans, supporting the theory of seafloor spreading.

Magnetic Stripes

Symmetrical magnetic stripes observed on either side of mid-ocean ridges reflect the Earth’s magnetic field orientation at the time of magma cooling.

Plate Boundaries

The distribution of volcanoes and earthquakes helps us identify the boundaries of tectonic plates.

Tectonic Plates

Tectonic plates are fragments of the lithosphere that exhibit movement.

Continental Shelf and Talud

The continental shelf is the submerged extension of continents. The talud marks the edge of the continental shelf.

Types of Plate Movement

Separation (Divergent)

Plates separate at mid-ocean ridges.

Approaching (Convergent)

One plate subducts beneath another.

Sliding (Transform)

Plates slide past each other.

Movement of Separation (Divergent Boundaries)

At mid-ocean ridges, the following occurs:

  • Single-continental lithosphere
  • Upwelling of magma
  • Break in the lithosphere
  • Magma ascent
  • Formation of lakes
  • Magmatic material, denser than continental crust, creates a depression
  • Connection with the ocean
  • Formation or separation of continents, such as the Great Lakes area in Africa

Geological Phenomena at Divergent Boundaries

  • Volcanoes
  • Earthquakes (including undersea earthquakes that can cause tsunamis)
  • Mountain ridges

When Two Plates Collide (Convergent Boundaries)

  1. Oceanic-Oceanic: Both plates are dense, and one subducts beneath the other.
  2. Oceanic-Continental: The oceanic plate subducts beneath the continental plate.
  3. Continental-Continental: Mountain ranges form, magma extrusion is limited, and earthquakes are common.

Sliding Plates (Transform Boundaries)

An example is the California peninsula on the North American plate. These boundaries are characterized by faults, frequent earthquakes, and a lack of volcanoes.

In 1960, relationships between these aspects began to emerge, leading to the development of plate tectonics and the discovery of supporting evidence.

Plate Tectonics Summary

Plate tectonics can be summarized in three points:

  1. The Earth’s surface is divided into rigid pieces called lithospheric plates.
  2. These plates are not static but change slowly and continuously in size, shape, and position.
  3. The dynamic movement of lithospheric plates generates immense pressure, triggering various geological processes and influencing both internal and external phenomena.

Plate Boundary Types

  1. Convergent boundaries: Plates collide.
  2. Divergent boundaries: Plates separate.
  3. Transform boundaries: Plates slide laterally past each other.