11 Questions
What is the thinnest layer of the Earth?
Crust
Which part of the Earth is an area of hot molten rock beneath the Earth's crust?
Mantle
What is the approximate temperature of the thinnest layer under deep oceans?
1,200 °C
Why is oceanic crust generally younger than continental crust?
Oceanic crust is continually being created by volcanic eruptions
What rocks make up the continental crust?
Rocks with high silica content like granite
What is the main cause of plate movement in the Earth's crust?
Convection currents in the mantle
Which part of the Earth is solid and composed of iron and nickel?
Inner core
Where are earthquakes and volcanoes most likely to occur?
On tectonic plate boundaries
What is the approximate thickness of the core central part of the Earth?
3,400 km
How do plates move when convection currents converge near the Earth's crust?
They collide and move towards each other
What is a notable feature of the outer core in terms of its physical state?
It is made of liquid iron and nickel
Study Notes
Structure of the Earth
- The Earth is a sphere with a diameter of approximately 12,700 km and a circumference of 40,075 km at the equator.
- The distance from the centre of the Earth to its surface is about 6,371 km.
The Crust
- The crust is the outer solid layer of the Earth, with a thickness of about 20 km.
- It is the thinnest layer, composed of hard rock, with temperatures of approximately 1,200°C.
- The crust is divided into two parts: the oceanic crust and the continental crust.
- The oceanic crust is the thinnest part, making up the oceans, and is composed of heavier rocks rich in magnesium and iron.
- The continental crust is the thickest part, making up the continents, and is composed of rocks rich in silica, such as granite.
The Mantle
- The mantle is a layer of hot, molten rock beneath the Earth's crust, with a thickness of about 2,900 km.
- The top layer of the mantle is made of hard rock, while the lower part is semi-molten rock.
- The temperatures of 5,000°C cause convection currents, which move rock in the mantle.
The Core
- The core is the central part of the Earth, with a thickness of about 3,400 km.
- The core is divided into two parts: the inner core and the outer core.
- The inner core is a solid part, made up of solid iron and nickel, with a thickness of about 1,400 km.
- The outer core is a liquid part, made up of liquid iron and nickel, with a thickness of about 2,000 km, and has a temperature of 5,000°C and a very high pressure.
Plate Tectonics
- The Earth's crust is divided into giant slabs or pieces called tectonic plates.
- Tectonic plates can be thousands of kilometres wide and can have whole continents on them.
- The central core of the Earth is very hot, causing convection currents in the rock, which move through the Earth's mantle and cause plate movement in the crust.
- The tectonic plates move very slowly along the edges, which are called plate margins or plate boundaries, at a speed of between one and ten centimeters a year.
- Earthquakes and volcanoes are the result of plate movements and are most likely to occur either on or near plate boundaries.
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