🪨 The Rock Cycle

What you’ll learn

1. Igneous RocksUnderstand that igneous rock forms when molten magma or lava cools and hardens, and that cooling speed controls crystal size.Igneous rock forms when molten magma or lava cools and turns solid. Granite cools slowly deep underground and grows large crystals, while basalt cools quickly at the surface and is dark and fine-grained. Cooling speed is the key to how big the crystals are.
2. Sedimentary RocksUnderstand that sedimentary rock forms from layers of sediment that are compacted and cemented, and often shows layers and fossils.Sedimentary rock forms when sediment, tiny pieces of rock, sand and shell, settles, is buried, and is compacted and cemented over a long time. Sandstone and limestone form this way. Because it builds up gently in layers, sedimentary rock often shows visible bands and can hold fossils.
3. Metamorphic Rocks and the CycleUnderstand that metamorphic rock is changed by heat and pressure, and how all three rock types link together in the rock cycle.Metamorphic rock is existing rock changed by great heat and pressure without melting, such as limestone into marble or mudstone into slate. The rock cycle links all three families: weathering and erosion make sediment for sedimentary rock, heat and pressure make metamorphic rock, and melting then cooling makes igneous rock, in a never-ending loop over millions of years.

Questions this course answers

Grounded in trusted sources

• USGS
• BBC Bitesize
• Britannica

Every Wunder lesson is built from real, reputable sources — never invented.

Related Science courses