1.1 What is the Plate tectonic theory Flashcards
1
Q
General plate tectonic theory
A
- Earth has a three-layered structure.
- The Earth’s lithosphere is broken up into tectonic plates.
- Tectonic plates are constantly moving.
- Plate movements result in the formation of major landforms we find on the Earth’s surface, such as volcanoes, fold mountain ranges, and oceanic trenches. It also explains the occurrence of certain phenomena, such as earthquakes and tsunamis
2
Q
Layers of the earth
A
- Core
- Mantle
- Crust
3
Q
Core
A
- innermost layer
- hottest layer : 4400 to 6000ºC
- thickest layer of 3300km
4
Q
Mantle
A
- lies above the core
- 1000 to 3700ºC
- about 2900km thick
5
Q
Crust
A
- outermost layer
- thinnest layer, 6 to 70 km
6
Q
Parts of layers of earth
A
Mantle is made up of the:
1. uppermost mantle
2. Asthenosphere
3. lowermost mantle
Lithosphere (solid parts of earth) is made up of the:
1. Crust
2. Uppermost mantle
7
Q
Lithosphere
A
Types of lithosphere:
1. Continental crust (continental lithosphere)
2. Oceanic crust (oceanic lithosphere)
Oceanic crust is denser than continental crust
Lithosphere is divided into tectonic plates
8
Q
Continental Crust (CC)
A
- layer of granitic, sedimentary and metamorphic rocks, which forms the continents and areas of shallow seabed close to the shores
- thicker CC covers 40% of earth’s surface, while the thinner OC covers the rest
- comprises of mainly lighter granitic rocks
9
Q
Oceanic Crust (OC)
A
- extends 5-10km beneath ocean floor
- composed of diff types of basalts
- comprises of mainly heavier granitic rocks
10
Q
Global plate movement
A
- plates lie on top of semi-solid mantle
- plates move relative to each other at constant motion
- landforms such as mountains and volcanoes are created
11
Q
Plate boundaries
A
- Divergent plate boundaries (plates are moving away from each other)
- Convergent plate boundaries (plates are moving towards each other)
- Transform plate boundaries (plates are sliding horizontally past each other)
12
Q
What drives tectonic plate movement
A
- convention currents
- slab-pull force
13
Q
Convention Driven Plate Movement
A
- main driving force of plate movement
- heat from the Earth’s core causes the material in the mantle to become less dense and rise towards the surface.
- Since hotter, less dense material rises while colder, denser material sinks.
- The rising material in the mantle spreads horizontal under the more rigid crust, exerting a driving force on the overlying plates and dragging them apart causing divergent plate movement
- The material in the mantle then loses heat, becoming denser and sinking towards the core
- Convergent plate movement occurs where convention currents collide
- Mental moving to core then gets heated up again and the process repeats.
- This rising and sinking of the mantle material form a current known as convection currents
14
Q
Slab-pull force
A
- gravity-controlled subduction of denser OC
- subduction along drag the rest of the plate along with it, causing plates to move
15
Q
Tectonic subduction
A
- occurs mostly at suduction zones where OC subduct under CC
- when two plates converge/move towards each other, the denser oceanic crust is pulled down by gravity as it subduct beneath the less dense crust.
- The denser oceanic crust sinks deeper into the mantle under its own weight, pulling the rest of the plate with it. This results in further convergence.
- in situations where subducted part of the plate gets detached from the plate, sinking into the mantle w/o exerting much slab-pull force
- instead, detached part induces convention in mantle that creates a suction forces that drives plate movements
