MECHANISM OF PLATE TECTONICS: CONVECTION CURRENT, SLAB PULL & RIDGE PUSH | SCIENCE 10 - Week 7

Summary

This week's lesson delves into the forces behind plate tectonics: convection currents, slab pull, and ridge push. Convection currents, likened to a conveyor belt, drive plate movement through the sinking and rising of hot and cold materials in the mantle. Slab pull theory attributes plate movement to the gravitational pull of subducting plates, while ridge push, occurring at mid-ocean ridges, is a gravity-driven force where lithosphere slides down the elevated asthenosphere. These mechanisms collectively explain the causes of plate tectonics.

Takeaways

• 🌏 This week's discussion focuses on the possible causes of plate movements, including slab pull, ridge push, and convection currents.
• 🔍 The lesson aims to describe convection current, slab pull, and ridge push, and to explain what causes plate tectonics.
• 🔄 Convection current is likened to a conveyor belt, driving plate movement through the sinking of hot, soft rocks in the asthenosphere, creating a continuous loop.
• 🌋 Convection cells in the mantle are essential for plate tectonics, transferring heat to the surface faster than conduction alone.
• 🌀 Arthur Holmes proposed that convection currents in the mantle cause the plates to move, with heated material rising and cooled material sinking, creating a circling behavior.
• 📉 The slab pull theory suggests that the weight of the tectonic plate itself, through the subduction process, is a driving force for plate tectonics.
• 🌐 The ridge push force is a result of the lithosphere sliding down the slope of the asthenosphere at mid-ocean ridges due to gravity.
• 🌌 The asthenosphere is a less dense, soft, and plastic zone that allows the overriding plate to slide, contributing to plate movement.
• 🏔 The ridge push force increases towards the subduction zone as the plate gets thicker and denser away from the spreading center.
• 📚 The lesson concludes by summarizing the three forces that interact to create plate motion: convection current, slab pull, and ridge push.

Q & A

What are the three forces discussed in the script that interact to create plate motion?

The three forces discussed are convection current, slab pull, and ridge push.

How does a convection current function in relation to plate tectonics?

A convection current in plate tectonics refers to the continuous loop of sinking hot, soft rocks caused by energy transfer in the asthenosphere, creating loops of sinking and rising materials in the mantle, which pushes the magma up, forming new crusts and exerting a lateral force on the plate.

What is a convection cell and how does it relate to plate tectonics?

A convection cell is a circular pattern created by convection within the mantle, where hot material rises and cold material sinks, creating cycles that push the magma up and apart, contributing to seafloor spreading and plate movement.

Who proposed the theory of mantle convection, and what is the essence of this theory?

Arthur Holmes proposed the theory of mantle convection, which suggests that as the mantle becomes heated, its density decreases, causing it to rise, and when it cools, it sinks, exhibiting a circling behavior that drives plate motion.

What is the slab pull theory and how does it cause plate tectonics?

The slab pull theory states that the weight of the tectonic plate drives subduction in oceanic crust. As the slab is pulled down into the mantle, it drags the rest of the plate along with it, causing tectonic plate movement.

How does the density of a slab affect its movement according to slab pull theory?

According to slab pull theory, a denser slab will sink faster than a less dense slab due to gravitational pull, and it will exert a greater force on the plate attached to it, thus affecting plate movement.

What is ridge push and how does it contribute to plate motion?

Ridge push, or sliding plate force, is a force that occurs at mid-ocean ridges due to the rigid lithosphere sliding down the slope of the raised asthenosphere below. This gravity-driven mechanism results from the elevated position of the oceanic ridge, causing slabs of lithosphere to slide down the flux of the ridge.

What is the role of the asthenosphere in ridge push?

The asthenosphere acts as a zone of soft, plastic material which is less dense than the riding plate above it, acting as a massive shear zone for the overriding plate, allowing the plate to slide down the slope of the asthenosphere due to the weight difference.

How does the difference in gravitational potential energy between a plate at its spreading center and subduction zone affect ridge push?

The difference in gravitational potential energy between a plate at its spreading center and subduction zone causes the plate to slide down the slope of the asthenosphere, with the ridge push force increasing towards the subduction zone as the plate gets thicker and denser away from the spreading center.

What is the relationship between convection currents and the formation of seafloor spreading?

Convection currents in the asthenosphere push magma up, forming new crusts, and exert a lateral force on the plate, which pushes it apart to create seafloor spreading.