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.

Outlines

00:00

🌏 Plate Tectonics Forces: Convection Currents, Slab Pull, and Ridge Push

This week's discussion on plate tectonics delves into the forces behind plate movements, including convection currents, slab pull, and ridge push. Convection currents are likened to a conveyor belt, transferring heat within the Earth and creating loops of sinking hot rocks in the asthenosphere. This process is essential for plate tectonics, with Arthur Holmes proposing that mantle convection drives plate motion. Slab pull theory suggests that the weight of the plate itself, particularly during subduction, is a significant force in plate tectonics. Demonstrated through a simple paper clip chain model, slab pull is a strong force that can drag plates along with it. Lastly, ridge push, proposed by a geologist, is a force that occurs at mid-ocean ridges due to the lithosphere sliding down the elevated asthenosphere. This gravity-driven mechanism is influenced by the difference in gravitational potential energy between a plate at its spreading center and the subduction zone.

05:03

🌌 The Mechanics of Ridge Push in Plate Tectonics

The second lesson focuses on the ridge push mechanism in plate tectonics. This force is a result of the rigid lithosphere sliding down the elevated asthenosphere beneath mid-ocean ridges. The model suggests that the elevated position of the oceanic ridge causes lithospheric slabs to slide down, driven by gravity. The asthenosphere, being less dense and acting as a shear zone, allows the plate to slide down the slope due to the weight difference between the plate and its spreading center. As the plate moves away from the spreading center and towards the subduction zone, it thickens and becomes denser, increasing the ridge push force. This lesson concludes with a summary of the key points and a thank you to the viewers for their attention.

Keywords

💡Plate Tectonics

Plate tectonics is a theory in Earth's science that describes the large-scale motion of Earth's lithosphere. The lithosphere is divided into several large plates that move over the asthenosphere, which is a more fluid layer of the mantle. This movement is responsible for various geological phenomena such as earthquakes, volcanic activity, and the formation of mountain ranges. In the video, plate tectonics is the central theme, with the discussion focusing on the forces that cause the plates to move.

💡Convection Current

A convection current is a fluid motion that results from the combined effects of buoyancy and gravity acting on the fluid's density variations. In the Earth's mantle, convection currents are driven by heat, causing solid rock to behave plastically and move in a circular pattern, forming convection cells. These currents are crucial for plate tectonics as they push and pull the plates, leading to their movement. The video script likens convection currents to a conveyor belt, illustrating how they transfer heat and drive plate motion.

💡Slab Pull

Slab pull refers to the force exerted by the weight of a tectonic plate as it moves downward into the mantle during the process of subduction. This force is a result of gravity pulling the dense oceanic lithosphere into the asthenosphere. The video script uses the analogy of a paper clip chain to demonstrate how the weight of the plate (the 'slab') pulls the rest of the plate along, causing movement. This is one of the forces discussed as a potential cause of plate tectonics.

💡Ridge Push

Ridge push, also known as the sliding plate force, is the force that results from the elevated position of the oceanic ridge and the gravitational potential energy difference between the spreading center and the subduction zone. This force causes the lithosphere to slide down the slope of the asthenosphere, contributing to plate motion. The video script explains that as the plate gets thicker and denser away from the spreading center, the ridge push force increases towards the subduction zone.

💡Asthenosphere

The asthenosphere is a part of the Earth's mantle that lies just below the lithosphere. It is characterized by its partially molten and ductile nature, allowing it to flow slowly over geological timescales. In the context of the video, the asthenosphere is where convection currents occur, and it serves as a medium through which the forces of slab pull and ridge push are transmitted, facilitating plate movement.

💡Conduction

Conduction is a mode of heat transfer within a material without any movement of the material itself. It occurs when heat is directly transferred through a solid from a region of higher temperature to a region of lower temperature. The video contrasts conduction with convection, explaining that convection currents in the mantle are more effective at transferring heat to the surface than conduction alone.

💡Subduction

Subduction is a geological process where one tectonic plate moves under another and is forced into the mantle due to gravitational forces. This process typically occurs at convergent boundaries where an oceanic plate meets a continental plate. In the video, subduction is discussed as a key process in slab pull theory, where the sinking of the oceanic plate into the mantle drags the rest of the plate along with it.

💡Mantle

The mantle is the layer of the Earth lying between the crust and the outer core. It is a thick, dense layer primarily composed of silicate rocks. In the video, the mantle is highlighted as the site of convection currents, which are essential for the movement of tectonic plates. The movement within the mantle drives the processes of plate tectonics.

💡Buoyancy

Buoyancy is the upward force exerted by a fluid that opposes the weight of an immersed object. In the context of the video, buoyancy is a key factor in the formation of convection currents. As hot material in the mantle becomes less dense and rises due to buoyancy, it creates a cycle of sinking cold material and rising warm material, which in turn drives plate movement.

💡Seafloor Spreading

Seafloor spreading is a process that occurs at mid-ocean ridges where new oceanic crust is formed through volcanic activity. As the magma rises and solidifies, it pushes the existing crust apart, causing the seafloor to spread outward. The video script mentions seafloor spreading as an example of how convection currents push magma up, forming new crusts and contributing to plate tectonics.

Highlights

Introduction to the seventh week of discussion on plate tectonics.

Focus on the possible causes of plate movements: slab pull, ridge push, and convection current.

Objectives: describe convection current, slab pull, and ridge push; explain what causes plate tectonics.

Convection current: a force that drives plate movement, similar to a conveyor belt.

Definition of convection current: a continuous loop of sinking hot, soft rocks in the asthenosphere.

Convection cell: a circular pattern that carries heat to the mantle's surface.

Convection in the mantle is essential for plate tectonics, behaving like convection in a pot on a stove.

Convection currents in the asthenosphere drive plate motion, as proposed by Arthur Holmes.

Slab pull theory: gravity and the plates themselves are responsible for plate tectonics through subduction.

Demonstration of slab pull using a paper clip chain to represent subducting tectonic plates.

Slab pull is a strong force that drives subducting tectonic plates due to the weight of the plate.

Slab pull theory suggests that mantle convection is a product of subduction, not the cause of plate tectonics.

Ridge push: a driving force for plate motion at mid-ocean ridges due to the sliding of the lithosphere.

Ridge push model proposed by a geologist, stating that the pushing on plates is due to gravitational potential energy differences.

The asthenosphere acts as a shear zone for the overriding plate, allowing it to slide down the slope of the ridge.

Ridge push force increases towards the subduction zone as the plate gets thicker and denser away from the spreading center.

Conclusion of the lesson, summarizing the three forces that cause plate tectonics.

Transcripts

hello great and

welcome to the seventh week of our

discussion on plate tectonics

now this week let's talk about the

possible causes of blade movements and

that includes the slab pool

the rich push and the convection current

at the end of the lesson you should be

able to one

describe convection current slab pull

and reach push and number two explain

what causes plate tectonics

there are three forces that interact to

create plate motion

we have the convection current the slab

pull theory

and the ridge push now let's explain how

each

force cause plate movement let's start

with

lesson one convection current

have you seen the apparatus where the

luggage of the travelers

are placed what do you call that device

[Music]

well that is a conveyor belt it is used

to transfer heavy objects from one point

to another

one of the forces that drives plate

movement works the same way the conveyor

belt does

and that is the conduction current now

what

is a convection current convection helps

to move

heat within the earth convection current

refers to the continuous loop of sinking

hot

soft rocks caused by energy transfer in

the asthenosphere

convection creates loops of sinking and

rising materials in the mantle

this circular pattern is called

convection cell

this carries heat to the surface of the

mantle much faster than hitting by

conduction

a convecting mantle is essential feature

of plate tectonics

convection in the mantle behaves the

same way convection happens in a pot

soap on a hot stove

the material near the heat source

becomes hot and expands

making it less dense than the materials

above

buoyancy causes it to rise and cooler

materials flow

in from the sides then sinks at the

bottom

creating cycles of the sinking of cold

and rising of warm water

this convection circling within the

mantle pushed the magma up

forming new crusts and exerting a

lateral force

on the plate pushing it apart to create

seafloor spreading

when colder magma sinks during

convection it pulls the surface together

making the denser crust to subduct

convection currents in the asthenosphere

drive plate motion

this theory of mental convection was

proposed

by arthur holmes according to him

as the mantle became heated its density

decreases and eventually rise and up

when the material cooled it would sink

exhibiting a circling behavior that

would look like a conveyor belt

the pressure heated magma broke the

continents apart

forcing the pieces to drift in opposite

directions

he also speculated that when the

material sink

continents will be brought back together

again

next is lesson 2 slab pool theory

slab pool theory states that gravity and

the plates themselves are the ones

responsible for the plate tectonics

through subduction process to clearly

explain how slab

pool works let's take a closer look at

this simple demonstration

in here the paper clip chain represents

abducting tectonic plates

now look closely as to what happens as

the chain moves

off the edge this simple demonstration

explains that slab pull is a strong

force that drives abducting tectonic

plates

the weight of the tectonic plate drives

subduction in oceanic crust

as the slob is pulled down into the

mantle it drags the rest of the plate

along with it

causing tectonic plate movement a very

dense slab will sink faster than

a less dense slot because of the

gravitational pull

and it will exert greater force on the

plate attached to it

slab pool theory believes that mantle

convection

is not the cause of plate tectonics but

rather

it is a product of subduction

now we have lesson 3 the ridge push

ridge push or sliding plate force is a

proposed driving force

for blade motion in plate tectonics this

occurs at mid ocean ridges

as the result of the rigid lithosphere

sliding down the hut

raised asthenosphere below mid ocean

ridges

this gravity-driven mechanism results

from the elevated position

of the oceanic ridge which causes slabs

of lithosphere to slide down the flux

of the ridge this gravity sliding ridge

push model was proposed by

bot a geologist which states that the

pushing on the plates

is actually due to difference in

gravitational potential energy

between a plate at its spreading center

and subduction zone

the asthenosphere is a zone of soft

plastic material which is less

dense than the riding plate above it it

acts as a massive

shear zone for the overriding plate

the plate will effectively slide down

the slope of the asthenosphere

due to the weight difference between the

plate and its spreading center

and the subduction zone since the plate

gets

thicker and denser the farther away from

the spreading center

the ridge push force will increase

towards the subduction zone

and that ends our lesson i hope you

learned something today

thank you for watching

thank you