Big idea
The Earth is built of layers, its surface is made of moving plates, and rocks constantly recycle through the rock cycle.
01Earth's layers
The Earth has four main layers.
- Crust — thin, solid outer layer we live on
- Mantle — thick, mostly solid but able to flow slowly over long times
- Outer core — liquid, mostly iron and nickel
- Inner core — solid, extremely hot and under huge pressure
02Plate tectonics
The crust and top of the mantle are broken into huge pieces called tectonic plates, which float on the slowly flowing mantle below and move a few centimetres per year.
Where plates meet, they can collide, pull apart, or slide past each other — causing earthquakes, volcanoes, and mountain building.
03The rock cycle
Rocks are continually transformed between three types through heat, pressure, weathering and time.
- Igneous rock — forms when molten rock (magma or lava) cools and hardens
- Sedimentary rock — forms when layers of sediment are compressed over time
- Metamorphic rock — forms when existing rock is changed by heat and pressure without melting
04Earthquakes and volcanoes
Earthquakes happen when built-up stress at plate boundaries is suddenly released, sending out shock waves.
Volcanoes form where magma rises up through the crust, often at plate boundaries or over 'hot spots'.
| Term | 한국어 | Meaning |
|---|---|---|
| crust | 지각 | Earth's thin outer solid layer |
| mantle | 맨틀 | Thick layer beneath the crust that flows slowly |
| core | 핵 | Earth's centre, made of iron and nickel |
| tectonic plate | 지각판 | A huge moving piece of Earth's crust and upper mantle |
| igneous rock | 화성암 | Rock formed from cooled magma or lava |
| sedimentary rock | 퇴적암 | Rock formed from compressed sediment layers |
| metamorphic rock | 변성암 | Rock changed by heat and pressure without melting |
Quick check — tap a question to reveal the answer
List Earth's four layers from the surface down.
Crust, mantle, outer core, inner core.
What causes earthquakes?
The sudden release of stress built up at tectonic plate boundaries.
Which rock type forms when magma cools and hardens?
Igneous rock.