I need help on plate tectonics

#1
I need help understanding 'plate tectonic theory of crustal evolution':
- tectonic plate
- plate movement
- gravitational sliding
- ridge push
- slab pull
- convection currents
Please could someone explain this all to me? Thanks
0
5 years ago
#2
(Original post by Strawberrry)
I need help understanding 'plate tectonic theory of crustal evolution':
- tectonic plate
- plate movement
- gravitational sliding
- ridge push
- slab pull
- convection currents
Please could someone explain this all to me? Thanks
Hi Strawberrry, I've covered a lot of these in my degree so far. This is how I would describe/explain them:

Tectonic plate
The outer layer of the Earth (the lithosphere) is divided into several large slabs called tectonic plates, or lithosphere plates. Lithosphere plates comprise the crust (both oceanic and continental), plus the upper part (the top 100km or so) of the mantle, which is brittle, in contrast to the asthenosphere below, which is 'weak' due to a small degree (approximately 1%) of partial melting. Tectonic plates sit on top of the asthenosphere.

Plate movement
Plate movement refers to the movement of tectonic plates. Tectonic plates move relative to each other, driven by a series of different forces - slab pull, ridge push and trench suction are believed to be the most important forces driving plate movement.

Gravitational sliding
At mid-ocean ridges (large fractures in the oceanic crust through which magma is being released to form new ocean floor), hot buoyant magma rising underneath the ridge pushes the ocean floor upwards, producing a topographic high. Gravitational instability means that the crust naturally wants to sink back down, and as it moves away from the ridge, cools and becomes more dense, it begins to subside towards the mantle - this process is known as gravitational sliding.

Ridge push
Ridge push is one of the forces which is thought to drive plate movement. It works in two ways: 1) plates are pushed apart by the injection of magma at mid-ocean ridges, and 2) gravitational instability, due to the topographic high at the mid-ocean ridge (caused by the hot buoyant material pushing the ridge up), making the plates wanting to move downwards away from the ridge.

Slab pull
Slab pull is another force which drives plate movement. The idea is that the subducting plate is more dense than the surrounding mantle, so it subducts more quickly under its own weight due to gravity.

Convection currents
Convection currents occur in both the mantle and the outer core (due to the outer core of the Earth being liquid), but I'll just describe mantle convection here.

Material at the base of the mantle gets heated by the heat radiating from the core. This hotter material expands and becomes less dense, rising up through the cooler mantle rocks towards the surface. When the hot material reaches the base of the crust, it spreads out laterally, allowing time for the heat to be transferred into the crustal rocks via conduction. As the mantle material cools, it contracts and becomes more dense, then sinks back down towards the outer core before getting heated up again. These convection loops are thought to drive plate tectonics.

Sea floor spreading is where new material is being created at mid-ocean ridges, and the plates are moving apart, away from the mid-ocean ridges.

I hope this helps
4
#3
(Original post by Leviathan1741)
Hi Strawberrry, I've covered a lot of these in my degree so far. This is how I would describe/explain them:

Tectonic plate
The outer layer of the Earth (the lithosphere) is divided into several large slabs called tectonic plates, or lithosphere plates. Lithosphere plates comprise the crust (both oceanic and continental), plus the upper part (the top 100km or so) of the mantle, which is brittle, in contrast to the asthenosphere below, which is 'weak' due to a small degree (approximately 1%) of partial melting. Tectonic plates sit on top of the asthenosphere.

Plate movement
Plate movement refers to the movement of tectonic plates. Tectonic plates move relative to each other, driven by a series of different forces - slab pull, ridge push and trench suction are believed to be the most important forces driving plate movement.

Gravitational sliding
At mid-ocean ridges (large fractures in the oceanic crust through which magma is being released to form new ocean floor), hot buoyant magma rising underneath the ridge pushes the ocean floor upwards, producing a topographic high. Gravitational instability means that the crust naturally wants to sink back down, and as it moves away from the ridge, cools and becomes more dense, it begins to subside towards the mantle - this process is known as gravitational sliding.

Ridge push
Ridge push is one of the forces which is thought to drive plate movement. It works in two ways: 1) plates are pushed apart by the injection of magma at mid-ocean ridges, and 2) gravitational instability, due to the topographic high at the mid-ocean ridge (caused by the hot buoyant material pushing the ridge up), making the plates wanting to move downwards away from the ridge.

Slab pull
Slab pull is another force which drives plate movement. The idea is that the subducting plate is more dense than the surrounding mantle, so it subducts more quickly under its own weight due to gravity.

Convection currents
Convection currents occur in both the mantle and the outer core (due to the outer core of the Earth being liquid), but I'll just describe mantle convection here.

Material at the base of the mantle gets heated by the heat radiating from the core. This hotter material expands and becomes less dense, rising up through the cooler mantle rocks towards the surface. When the hot material reaches the base of the crust, it spreads out laterally, allowing time for the heat to be transferred into the crustal rocks via conduction. As the mantle material cools, it contracts and becomes more dense, then sinks back down towards the outer core before getting heated up again. These convection loops are thought to drive plate tectonics.

Sea floor spreading is where new material is being created at mid-ocean ridges, and the plates are moving apart, away from the mid-ocean ridges.

I hope this helps
Thank you so much! Makes much more sense
1
5 years ago
#4
(Original post by Strawberrry)
Thank you so much! Makes much more sense
You're welcome!
0
#5
(Original post by Leviathan1741)
You're welcome!
Hiya. I have another question. Could you tell me if these are right, I'm not too sure? The plate margins and associated landforms:
Ocean ridge - Constructive
Rift Valley - Constructive
Deep sea trenches - Destructive
Island arcs - Constructive
Young fold mountains - Destructive
Volcanoes - hot spot, destructive (e.g subduction zones) and constructive (e.g ocean ridges)
0
5 years ago
#6
0
5 years ago
#7
(Original post by Strawberrry)
Hiya. I have another question. Could you tell me if these are right, I'm not too sure? The plate margins and associated landforms:
Ocean ridge - Constructive
Rift Valley - Constructive
Deep sea trenches - Destructive
Island arcs - Constructive
Young fold mountains - Destructive
Volcanoes - hot spot, destructive (e.g subduction zones) and constructive (e.g ocean ridges)
These are all correct, however island arcs tend to form at destructive plate margins, where one oceanic plate is subducting underneath another oceanic plate
0
5 years ago
#8
(Original post by Strawberrry)
Hiya. I have another question. Could you tell me if these are right, I'm not too sure? The plate margins and associated landforms:
Ocean ridge - Constructive
Rift Valley - Constructive
Deep sea trenches - Destructive
Island arcs - Constructive
Young fold mountains - Destructive
Volcanoes - hot spot, destructive (e.g subduction zones) and constructive (e.g ocean ridges)
Island arcs are destructive, in constructive boundaries ocean crust forms. Rest is good.
0
#9
(Original post by Leviathan1741)
These are all correct, however island arcs tend to form at destructive plate margins, where one oceanic plate is subducting underneath another oceanic plate
Thanks again!
0
5 years ago
#10
(Original post by Strawberrry)
Thanks again!
No problem
0
5 years ago
#11
Post edited automatically
0
5 years ago
#12
(Original post by Kenya Not)
Why do you keep tagging me in threads? Geology and relationship advice isn't my forte...
0
5 years ago
#13
I like turtles.
0
5 years ago
#14
(Original post by Kenya Not)
I like turtles.
You should be tagging retro_turtles then
1
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