---
title: "The Rock Cycle"
description: "Explain the rock cycle: how igneous rocks form from magma, sedimentary rocks from compressed sediment, and metamorphic rocks from heat and pressure, and how all rock types can transform into one anoth"
canonical: https://lightmysky.com/learn/science/the-rock-cycle-mt_NckKLZ3uCE
source: https://lightmysky.com/learn/science/the-rock-cycle-mt_NckKLZ3uCE.md
retrieved: 2026-10-19
---

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# The Rock Cycle

Explain the rock cycle: how igneous rocks form from magma, sedimentary rocks from compressed sediment, and metamorphic rocks from heat and pressure, and how all rock types can transform into one another over geological time

Subject: Science · Area: Matter & Materials · Ages 12 to 14
Page: https://lightmysky.com/learn/science/the-rock-cycle-mt_NckKLZ3uCE

## Ready when they can

- Describes how each rock type (igneous, sedimentary, metamorphic) is formed
- Gives an example of each rock type and its formation (e.g. granite, limestone, marble)
- Traces a rock sample through possible transitions in the rock cycle
- Explains what geological time means and why rock cycle changes are slow

## Lesson: The Rock Cycle

Every rock on Earth belongs to one of three families: igneous, sedimentary, or metamorphic. What decides the family isn't what a rock looks like, it's how the rock formed. And here's the surprising part: given enough time, any rock can leave one family and join another.

*(drawing: Follow the loop: magma cools into igneous rock, weathers into sediment, gets pressed into sedimentary rock, then heat and pressure turn it metamorphic, which can melt again into magma.)*

Igneous rocks form when magma, melted rock from deep underground, cools and hardens. Cool it slowly underground and the crystals have time to grow large, like in granite. Cool it fast at the surface, as lava, and the crystals stay too small to see.

**Example.** Limestone tells the sedimentary story. Tiny shells, sand, and mud settle on an ocean floor and pile up in layers. New layers keep adding weight on top, and over millions of years that pressure squeezes the loose sediment into solid rock.

**Tip.** Push that same limestone deep underground, where heat and pressure squeeze it hard without melting it, and its minerals rearrange into marble, a metamorphic rock. Metamorphic means changed form, and marble never turned to liquid to get there.

**Recap.** Rocks form by cooling from magma, by squeezing sediment, or by heat and pressure underground, and over geological time, every rock type can turn into another.

## Practice

8 questions on this page, each with its working shown.

## Needs first

- [How Tectonic Plates Move](https://lightmysky.com/learn/science/how-tectonic-plates-move-mt_gv_uoHkdjR)
- [Properties of rocks](https://lightmysky.com/learn/science/properties-of-rocks-mt_R6YoRXkRxS)
- [Rocks and soil](https://lightmysky.com/learn/science/rocks-and-soil-mt_yhhprm7dZK)
- [How Rocks Change Over Time](https://lightmysky.com/learn/science/how-rocks-change-over-time-mt_z7AJZapsJj)

## Opens up

- [Minerals and the Three Rock Families](https://lightmysky.com/learn/science/minerals-and-the-three-rock-families-mt_S0edEKh084)