Plate Tectonics Theory - UPSC Geography Notes

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Plate Tectonics Theory

• Developed in the mid-20th century as an extension of the Continental Drift Theory proposed by Alfred Wegener.
• Plate tectonics explains the movement and interaction of Earth's lithospheric plates.
• The Earth's lithosphere is divided into several large plates, including major ones such as the Eurasian Plate, African Plate, Pacific Plate, and others.
• Three types of plate boundaries:

1. Divergent boundaries: Plates move away from each other, creating new crust through seafloor spreading. Examples include the Mid-Atlantic Ridge and the East African Rift Zone.
2. Convergent boundaries: Plates collide, leading to the formation of mountain ranges, volcanic activity, and earthquakes. Three types of convergent boundaries:

• Oceanic-Continental convergence: Oceanic plate subducts beneath the continental plate, creating volcanic arcs. Example: Andes Mountains.
• Oceanic-Oceanic convergence: One oceanic plate subducts beneath another, forming volcanic island arcs. Example: Japan.
• Continental-Continental convergence: Two continental plates collide, resulting in intense folding and uplifting of rocks. Example: Himalayas.

3. Transform boundaries: Plates slide past each other horizontally, causing frequent earthquakes. Example: San Andreas Fault in California.

• Plate tectonics is driven by convection currents in the Earth's asthenosphere, a partially molten layer below the lithosphere.
• Heat from the Earth's core creates these convection currents, which cause the plates to move.
• The movement of plates is relatively slow, ranging from a few centimeters to several centimeters per year.
• Plate boundaries are dynamic zones with various geological phenomena:

1. Earthquakes: Occur at all types of plate boundaries due to the accumulation and release of stress along fault lines.
2. Volcanic activity: Primarily associated with convergent and divergent boundaries where magma rises to the surface.
3. Mountain building: Convergent boundaries result in the uplift of large mountain ranges through compression and folding of rocks.

Plate tectonics theory provides a comprehensive framework to understand Earth's geological processes and the distribution of geological features. It explains the formation of major features like mountain ranges, volcanic arcs, ocean basins, and the movement of continents.

The theory also helps in understanding the distribution of natural resources, such as minerals and fossil fuels. Plate tectonics plays a vital role in shaping Earth's surface and influencing climate patterns through the formation of landforms and oceanic circulation.

Note: Plate tectonics theory revolutionized the field of Earth sciences, providing a unifying explanation for various geological phenomena and processes. It continues to be a fundamental concept in understanding the dynamic nature of our planet's lithosphere.