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Follow a grain of rock: worn away, buried, cooked, melted and born again.
Rock Cycle lab · Last updated: 16 October 2026
You follow a single grain of rock on a very long journey: worn away from a mountain, carried and buried, cooked deep underground, melted and born again as new rock. It shows that rocks are not permanent, and it explains the three main types of rock found in every school field and riverbed.
What you'll discover
- Igneous rock forms when melted rock cools and hardens, either underground or after a volcanic eruption.
- Sedimentary rock forms from layers of worn-away grains that are buried and pressed together.
- Heat and pressure deep underground change any rock into metamorphic rock, and enough heat melts it again.
The science in plain words
Geologists sort rocks into three main types by how they formed. Igneous rocks form when molten rock, called magma underground or lava at the surface, cools and turns solid. Granite cools slowly underground and has large crystals, while basalt cools quickly from lava and has tiny ones.
At the surface, rain, ice, wind and plants slowly break rocks into grains. Rivers, waves and wind carry these grains away and drop them in layers, often on the floor of a lake or sea. As more layers pile on top, the grains are squeezed together and minerals in the water cement them into sedimentary rock, such as sandstone, shale or limestone. Sedimentary rocks often contain fossils.
When rock is buried deep or caught where tectonic plates collide, intense heat and pressure change its minerals and texture without melting it. This makes metamorphic rock: limestone becomes marble, and shale becomes slate. If the heat rises further, the rock melts into magma, which may later cool into new igneous rock. Any rock can follow many routes round this cycle, and a single grain may take millions of years to complete one loop. The cycle is driven by heat from inside the Earth and by energy from the Sun, which powers weather and erosion.
Where it fits
- India, NCERT: The rock cycle is not part of the NCERT science syllabus for classes 6 to 10; it is taught in NCERT geography.
- United States: Grades 6 to 8
- Next Generation Science Standards: MS-ESS2-1
Common questions
What are the three types of rocks?
The three main types are igneous rocks, formed from cooled molten rock, such as granite and basalt; sedimentary rocks, formed from layers of compressed grains, such as sandstone and limestone; and metamorphic rocks, changed by heat and pressure, such as marble and slate.
How long does the rock cycle take?
The rock cycle usually takes millions of years. Some steps can be fast: lava can cool into rock within days, and a landslide moves rock in seconds. But burying, squeezing and melting rock deep underground happens extremely slowly, so a full loop is very long.
Why do some rocks have fossils?
Fossils are usually found in sedimentary rocks. When a plant or animal dies and is quickly covered by mud or sand, its remains can be preserved as the sediment hardens into rock. Igneous rock forms from molten material, which would destroy any remains.
Related labs
- Volcanic Eruption: Why do some volcanoes pour out rivers of lava, and others explode?
- Erosion: Pour water on a slope of sand: where does the sand go?
- Plate Tectonics: The ground moves as fast as your fingernails grow. What does that do in a million years?
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Try it yourself
The Rock Cycle lab is one of the interactive 3D science labs inside Taz. Change one thing, predict what will happen, then run it and watch. Labs open after you sign in.