Types of Rock
Know the three main types of rock — igneous (formed when lava or magma cools), sedimentary (formed from layers pressed together), and metamorphic — and that fossils are found in sedimentary rock
What a learner can do afterwards
- Name the three main rock types: igneous, sedimentary, metamorphic
- Explain that igneous rock forms when lava or magma cools and hardens
- State that fossils are preserved in sedimentary rock because it forms in layers
The lesson
Look down at the ground you are standing on. It is made of rock, but rocks are not all the same. Scientists sort every rock into one of three types, based on how it formed. The three types are igneous, sedimentary, and metamorphic.
Ben watches a volcano video. He sees bright red lava flow down the mountain, then slowly cool until it turns into hard, dark rock. That rock is igneous rock. Melted rock underground is called magma, and melted rock that reaches the surface is called lava. When magma or lava cools and hardens, it becomes igneous rock.
Metamorphic rock is the third type. It forms when heat and heavy pressing squeeze another rock, deep underground, into something new. Only sedimentary rock forms slowly in layers, so that is the only place you will find fossils.
Igneous cools from melted rock, sedimentary presses together in layers and can hold fossils, and metamorphic gets squeezed and heated into something new.
Watch it
Where it sits
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.