--- title: "Types of rocks" description: "Use vocabulary for Earth's geological processes and rock types — igneous, sedimentary, metamorphic, erosion, weathering, deposition, fossil, sediment, strata, permeable, impermeable — and apply these " canonical: https://lightmysky.com/learn/science/types-of-rocks-mt_bqL8DD1SbV source: https://lightmysky.com/learn/science/types-of-rocks-mt_bqL8DD1SbV.md retrieved: 2026-10-19 --- > **Agent view.** This is the Markdown twin of the page, for tools and assistants. > When to use this site, and the call that answers each job: https://lightmysky.com/agent-instructions.md > API description (OpenAPI 3.1): https://lightmysky.com/openapi.json · Authentication: https://lightmysky.com/auth.md > Pricing: https://lightmysky.com/pricing.md · Catalog: https://lightmysky.com/llms.txt · Full catalog: https://lightmysky.com/llms-full.txt > Every machine-readable file on this domain: https://lightmysky.com/.well-known/ai-catalog.json > Ask for Markdown with `Accept: text/markdown`, a `.md` address, or `?mode=agent`. # Types of rocks Use vocabulary for Earth's geological processes and rock types — igneous, sedimentary, metamorphic, erosion, weathering, deposition, fossil, sediment, strata, permeable, impermeable — and apply these when explaining how rocks form and how landscapes change over time Subject: Science · Area: Earth's Systems · Ages 9 to 11 Page: https://lightmysky.com/learn/science/types-of-rocks-mt_bqL8DD1SbV ## Ready when they can - Correctly classify igneous, sedimentary, and metamorphic rocks and explain in one sentence how each type forms - Use 'erosion', 'weathering', and 'deposition' correctly as three distinct stages in a sequence - Explain how fossils form using 'sediment' and 'sedimentary rock' correctly ## Lesson: Types of rocks Every rock on Earth is one of three types: igneous, sedimentary, or metamorphic. The type tells you the story of how that rock was made. Igneous rock forms when melted rock, called magma, cools and hardens into solid stone. If the magma cools slowly underground, the rock grows big crystals. If lava cools fast on the surface, the crystals stay too small to see. Sedimentary rock forms differently. Wind and water carry tiny bits of rock and sand, called sediment, and drop them in layers called strata. Over thousands of years, new layers press down on the old ones until the sediment squeezes into solid rock. Some sedimentary rock, like sandstone, is permeable, which means water can soak through it. Other rock is impermeable, which means water cannot pass through. *(drawing: Weathering breaks the rock apart where it sits. Erosion carries the broken pieces away. Deposition drops them in a new place.)* **Example.** A fish dies and sinks to the bottom of a lake. Sediment slowly covers its body, and more sediment keeps piling on top for thousands of years. The sediment turns into sedimentary rock, and the shape of the fish stays pressed inside it. That is a fossil. **Tip.** Metamorphic rock forms when heat and pressure inside the Earth squeeze an existing rock without melting it, changing it into a new kind of rock. Remember: weathering breaks rock apart, erosion moves the pieces away, and deposition drops them somewhere new. Three different jobs, three different words. **Recap.** Igneous, sedimentary, and metamorphic rocks form in different ways, and weathering, erosion, and deposition are three separate steps, not one blurry process. ## Practice 8 questions on this page, each with its working shown. ## Opens up - [Finding patterns in data](https://lightmysky.com/learn/science/finding-patterns-in-data-mt_-G6erQvLig) - [Rock layers and Earth's history](https://lightmysky.com/learn/science/rock-layers-and-earths-history-mt_0_K-GrKQpd) - [Rock layers as evidence of change](https://lightmysky.com/learn/science/rock-layers-as-evidence-of-change-mt_GheLsWvrJ4) - [How Earth systems interact](https://lightmysky.com/learn/science/how-earth-systems-interact-mt_LKagN9GJPX) - [Erosion and weathering](https://lightmysky.com/learn/science/erosion-and-weathering-mt_vAP_A986IQ)