๐ Planet Earth ๐ Rocks and minerals
Rocks
๐ In short
Rocks are the solid part of the Earth. Under the soil, sand and seas there are layers of rock. They're not all the same: every rock has a story of how it formed and where it came from. Scientists sort them into three kinds.
๐คฉ Did you know?
- Underground, magma is between 750 and 1250 degrees.
- Volcanic bombs can be more than 30 centimeters across.
- Pumice is a volcanic rock full of bubbles that floats on water!
- The pyramids were built of limestone and granite.
๐ Find out more
๐ Igneous rocks
Igneous rocks form when very hot melted rock cools and hardens, either underground, like coarse-grained granite, or on the surface after coming out of volcanoes, like basalt.
๐ Sedimentary rocks
Sedimentary rocks form from layers of sand, mud and shells that pile up on the floor of seas and lakes, then get squeezed and harden over time, like sandstone and limestone. These rocks are where we find fossils.
๐ก Metamorphic rocks
When rocks are put under great heat and pressure deep in the Earth, they change into new rocks, like marble, which forms from limestone.
๐ฏ The rock cycle
Rocks don't stay the same: they crumble, melt and change from one kind to another very slowly over millions of years, in a never-ending cycle.
๐ธ More pictures
๐งฉ Test yourself
1 How do igneous rocks form?
2 Which rock forms when limestone changes?
3 Volcanic bombs can be more than ?? centimeters across.
4 Which picture shows โRocksโ?
๐ Discover more
๐ท Picture sources: Wikimedia Commons
- Yogendra Joshi ยท CC BY 2.0
- Kotivalo ยท CC BY-SA 4.0
- DirkvdM ยท CC BY-SA 3.0
