Which phenomenon is most directly responsible for plate tectonics on Earth?
Show answer & explanation
Correct answer: B
Explanation
Solution: The correct answer is Convection currents in the mantle.
Explanation:
☛ Plate tectonics is driven primarily by convection currents operating within the Earth's mantle, particularly the semi-fluid asthenosphere.
☛ Tremendous heat generated from the Earth's core causes mantle material to heat up, expand, become less dense, and rise toward the crust.
☛ As the rising magma reaches the upper mantle, it cools, becomes denser, and sinks back down, forming a continuous circular flow known as a convection cell.
☛ The rigid tectonic plates of the lithosphere float on top of this moving mantle layer, causing them to collide, separate, or slide past one another.
Extra Exam-Relevant Facts:
☛ Arthur Holmes first proposed the theory of mantle convection currents in the 1930s as a mechanism for continental drift.
☛ The Lithosphere consists of the crust and the uppermost solid part of the mantle, broken into seven major and several minor tectonic plates.
☛ Asthenosphere: The highly ductile, mechanically weak, and deforming region of the upper mantle situated directly below the lithosphere.
☛ Plate Boundaries: Tectonic interactions occur along three primary boundaries—divergent (moving apart), convergent (colliding), and transform (sliding past).
Important One-Liners for Upcoming Exams:
☛ Who proposed the Continental Drift Theory in 1912? → Alfred Wegener
☛ Which layer of Earth lies directly below the lithosphere and facilitates plate movement? → Asthenosphere
☛ What type of plate boundary creates mid-ocean ridges like the Mid-Atlantic Ridge? → Divergent boundary
☛ The Mariana Trench was formed due to which type of plate convergence? → Oceanic-Oceanic convergent boundary
☛ What is the boundary between the Earth's crust and mantle called? → Mohorovičić (Moho) discontinuity