Subject: Physical Geography

Mantle plumes are significant geological features that play a crucial role in understanding plate tectonics and the Earth's internal dynamics.

Definition and Characteristics of Mantle Plume

• A mantle plume is a concentrated upwelling of hot, buoyant rock material originating from deep within the Earth's mantle.
• These structures consist of a mushroom-shaped head followed by a narrow conduit or tail that connects to the source region.
• They are characterized by their high temperature (100-300°C hotter than surrounding mantle) and distinct geochemical signatures.

Structure and Formation

• Primary Components:
  • Plume Head: Large bulbous structure (800-1000 km diameter).
  • Plume Tail: Narrow feeding conduit (100-200 km diameter).
  • Source Region: Usually at the core-mantle boundary.

Role in Plate Tectonics

• Hotspot Formation:

  • Creates surface expressions like the La Réunion and Comores hotspots in the Indian Ocean.
  • Forms volcanic chains and seamounts through continuous magmatic activity.

• Lithospheric Modification:

  • Causes significant thermomechanical erosion of continental lithosphere.
  • Recent studies show the Réunion plume caused thinning of up to 130 km in the Indian craton.

• Plate Motion Influence:

  • Affects plate velocities through basal heating and mechanical weakening.
  • The Indian Plate's acceleration since 65 Ma is attributed to plume-lithosphere interaction.

Modern Understanding

• Seismic Tomography reveals:
  • Deep mantle structures beneath major hotspots.
  • Variations in lithospheric thickness.
  • Velocity anomalies indicating thermal perturbations.

Mantle plumes serve as fundamental drivers of plate tectonics, influencing everything from continental break-up to volcanic activity. Their study through modern techniques like seismic tomography and geochemical analysis continues to enhance our understanding of Earth's dynamic processes, particularly in regions like the Indian Ocean where multiple plumes interact with tectonic plates.