Lecture on Tectonic Plates Movement

Historical Context

• The concept of continental drift is over 200 years old.
• Widely accepted by geologists only since the 1960s.
• Earth's crust is composed of moving fragments known as tectonic plates.
• Modern technology allows us to track plate movement with millimeter precision from space.

Mechanism of Plate Movement

• Simplified Explanation: Tectonic plates move due to currents in the Earth's upper mantle.
  • Converging currents push plates together.
  • Diverging currents pull plates apart.
• Detailed Explanation:
  • Hot mantle rock rises from the core, cools, and sinks back.
  • Plates are not just passively riding these mantle currents.
  • Some plates, such as the Nazca Plate, move faster than the underlying mantle currents.

Additional Forces Influencing Plate Movement

• Plates move faster than mantle currents due to additional forces.
  • When ocean plates collide, the thinner plate bends and slides under the thicker one.
  • The sunken edge pulls the plate behind it, similar to a chain sliding off a table.
  • The larger the sunken portion of a plate, the harder it pulls, increasing speed.

Identifying Plate Movements

• Ocean trenches visible on maps, like Google Earth, indicate where ocean crust is plunging downward.
  • These trenches are deep and narrow, often off coasts or near island chains.

Role in Mantle Convection

• Sunken ocean crust slabs impact mantle convection.
  • Slabs block the sideway flow of mantle rock, forcing it to sink.
  • Eventually, slabs become too heavy, break off, and sink towards the core.
  • This creates a suction force that pulls mantle material with it.
  • Seafloor crust functions like part of a conveyor belt.

Contrast with Continents

• Continents are described as "baggage" on the moving tectonic plates, contrasting with seafloor crust that actively participates in the movement process.