Structure of the Earth
The structure of the Earth
- The Earth is composed of a number of layers
- Inner core: About 1400km in diameter, a solid and dense layer composed of iron and nickel with temperatures of about 5000 - 6000°C
- Outer core: About 2100km thick, a semi-molten metal layer with temperatures between about 4000-6000°C
- Mantle: About 2900km thick, a semi-molten layer which is less dense than the outer core this is split into two parts
- Asthenosphere
- Lower mantle
- Lithosphere: The thickness varies, and is made up of two types of crust together with the rigid upper part of the mantle.
- The two types of crust are:
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- Oceanic
- Continental
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Structure of the Earth
Crust
- There are two types of crust and they are part of the lithosphere:
- The oceanic crust is thinner (5-10km) but heavier, denser and is composed mainly of basalt
- The Continental crust is thicker (25-100km) but is older, denser and is composed mainly of granite
- Oceanic crust is continually being created and destroyed as a result of plate movement where it is denser and so subducts under the continental crust
Mantle
- The mantle is composed of the:
- Upper mantle which has two layers
- The rigid upper layer which is part of the lithosphere
- The Asthenosphere which is partially molten plastic type layer which moves under high pressure and is between 35-250km
- Lower mantle which is solid and the largest of the Earth's layers (2900km)
Worked example
Study Figure 1,
Identify which one of the following describes the outer core.
(1 mark)
A. a liquid layer of 2 200km in thickness | |
B. a solid layer with temperature 5000oC | |
C. a layer of molten and partly solid rock | |
D. a solid layer of 1 300km in thickness |
Answer:
- A - a liquid layer of 2200km in thickness