Plate Tectonics
Structure of the Earth
The Earth is divided into four main layers, the crust, the mantle, the outer core and the inner core.
Crust: The crust is solid and is the layer we live on. The crust is usually between 10km and 60km thick. The crust thickness is often referred to as the relative thickness of an apple skin (when compared to the size of an apple).
Mantle: This the thickest section of the earth with a diameter of about 2900km. The mantle is often described as being semi-molten, but in reality the top is hard rock and as you near the outer core it is beginning to melt (magma). Convection currents are found in the mantle.
Outer Core: This layer is believed to be liquid and largely made of iron and nickel. It is extremely hot with temperatures up to 5,500 degrees centigrade.
Inner Core: This layer is believed to be solid, because of the immense pressure placed upon it. It contains the centre of the earth which is about 6,378km from the surface. It is also extremely hot at about 5,500 degrees centigrade.
Sometimes you will here the crust and the upper layer of the mantle referred to as the lithosphere. Below the lithosphere but also in the mantle you find the asthenosphere. This region lies between 100km and 200km.
The Earth is divided into four main layers, the crust, the mantle, the outer core and the inner core.
Crust: The crust is solid and is the layer we live on. The crust is usually between 10km and 60km thick. The crust thickness is often referred to as the relative thickness of an apple skin (when compared to the size of an apple).
Mantle: This the thickest section of the earth with a diameter of about 2900km. The mantle is often described as being semi-molten, but in reality the top is hard rock and as you near the outer core it is beginning to melt (magma). Convection currents are found in the mantle.
Outer Core: This layer is believed to be liquid and largely made of iron and nickel. It is extremely hot with temperatures up to 5,500 degrees centigrade.
Inner Core: This layer is believed to be solid, because of the immense pressure placed upon it. It contains the centre of the earth which is about 6,378km from the surface. It is also extremely hot at about 5,500 degrees centigrade.
Sometimes you will here the crust and the upper layer of the mantle referred to as the lithosphere. Below the lithosphere but also in the mantle you find the asthenosphere. This region lies between 100km and 200km.
Tectonic Plates and the Earth's Crust
The crust of the earth is broken into giants pieces. These giant pieces are called tectonic plates, or often just plates. There are seven major or primary plates (African, Eurasian, North American, South American, Pacific, Indo-Australian and Antarctica). There are seven smaller secondary plates (Nazca, Cocos, Caribbean, Scotia, Arabian, Philippine and Juan de Fuca). Because the plates are so big they have faults and cracks in them so are sometimes divided into smaller tertiary plates as well. The earth's plates are being constantly moved by convection currents found in the mantle. We will learn next what convection currents are and how they have changed the shape of the earth.
There are two types of crust, oceanic and continental. Generally oceanic crust is found under the oceans and continental under land. Although plates are usually a combination of oceanic and continental crust, there are some key differences between the two types of crust. the key differences are listed below.
The crust of the earth is broken into giants pieces. These giant pieces are called tectonic plates, or often just plates. There are seven major or primary plates (African, Eurasian, North American, South American, Pacific, Indo-Australian and Antarctica). There are seven smaller secondary plates (Nazca, Cocos, Caribbean, Scotia, Arabian, Philippine and Juan de Fuca). Because the plates are so big they have faults and cracks in them so are sometimes divided into smaller tertiary plates as well. The earth's plates are being constantly moved by convection currents found in the mantle. We will learn next what convection currents are and how they have changed the shape of the earth.
There are two types of crust, oceanic and continental. Generally oceanic crust is found under the oceans and continental under land. Although plates are usually a combination of oceanic and continental crust, there are some key differences between the two types of crust. the key differences are listed below.
OCEANIC CRUST
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CONTINENTAL CRUST
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Oceanic and Continental Crust
Shifting Continents and Convection Currents
225 million years ago all the continents are believed to have been joined together in one supercontinent called Pangaea. Over millions of years, convection currents started moving the continents apart until there were two continents; Laurasia and Gondwanaland. Today the continents have moved even further apart, creating the land masses that we know today. The continents have not stopped moving so in the future the world will look different again, for example Europe and North America are actually moving apart at up to 10cm a year, but North America and Asia are moving closer together.
The tectonic plates are being moved by convection currents found within the mantle of the earth. Below is a summary of how convection currents work:
225 million years ago all the continents are believed to have been joined together in one supercontinent called Pangaea. Over millions of years, convection currents started moving the continents apart until there were two continents; Laurasia and Gondwanaland. Today the continents have moved even further apart, creating the land masses that we know today. The continents have not stopped moving so in the future the world will look different again, for example Europe and North America are actually moving apart at up to 10cm a year, but North America and Asia are moving closer together.
The tectonic plates are being moved by convection currents found within the mantle of the earth. Below is a summary of how convection currents work:
- Magma (semi-molten rock) near the outer core is heated.
- As the magma warms it expands and becomes less dense.
- The less dense magma then starts to rise towards the crust
- As the magma nears the crust it begins to cool.
- The cooling magma becomes denser and begins to sink
- The rising and falling magma creates circular currents with the mantle
- It are these currents that create friction with the crust above and causes it to move.
- The process is known as convection currents
Plate Boundaries (earthquakes and volcanoes)
Where two plates join, it is called a plate boundary. Plates may move towards each other at a boundary, away from each other or alongside each other. If you look at a map showing plate boundaries and earthquakes and volcanic activity there is a very strong relationship. Below we will look at plate boundaries and learn why there are earthquakes and volcanoes found at plate boundaries.
Where two plates join, it is called a plate boundary. Plates may move towards each other at a boundary, away from each other or alongside each other. If you look at a map showing plate boundaries and earthquakes and volcanic activity there is a very strong relationship. Below we will look at plate boundaries and learn why there are earthquakes and volcanoes found at plate boundaries.