---
title: "How Rocks Change Over Time"
description: "Understand the rock cycle: rocks slowly change from one type to another over millions of years — igneous rock weathers into sediment, sediment becomes sedimentary rock, heat and pressure create metamo"
canonical: https://lightmysky.com/learn/science/how-rocks-change-over-time-mt_z7AJZapsJj
source: https://lightmysky.com/learn/science/how-rocks-change-over-time-mt_z7AJZapsJj.md
retrieved: 2026-09-02
---

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# How Rocks Change Over Time

Understand the rock cycle: rocks slowly change from one type to another over millions of years — igneous rock weathers into sediment, sediment becomes sedimentary rock, heat and pressure create metamorphic rock, and melting starts the cycle again

Subject: Science · Area: Volcanoes & Earthquakes · Ages 9 to 11
Page: https://lightmysky.com/learn/science/how-rocks-change-over-time-mt_z7AJZapsJj

## Ready when they can

- Describe the rock cycle as a continuous process with no beginning or end
- Trace at least one complete path through the cycle from igneous to sedimentary to metamorphic and back
- Explain that the rock cycle operates over millions of years through weathering, pressure, heat, and melting

## Lesson: How Rocks Change Over Time

Rocks are always changing, just very slowly. Over millions of years, one type of rock can turn into another, and then into another. This never stops, and it has no true beginning and no true end, so scientists call it the rock cycle.

*(drawing: Follow the loop: igneous rock weathers into sediment, sediment becomes sedimentary rock, heat and pressure make metamorphic rock, and melting starts it all again.)*

**Example.** Picture a granite mountain, an igneous rock. Wind and rain slowly break it into tiny grains of sand. The sand piles up in a riverbed and presses together into sandstone, a sedimentary rock. Later, that sandstone gets buried deep underground, where heat and pressure squeeze it into quartzite, a metamorphic rock. If the quartzite ever melts, it becomes magma again, ready to cool into new igneous rock. Limestone takes the same road: heat and pressure turn it into marble.

**Tip.** This whole trip, from igneous rock to sediment to sedimentary rock to metamorphic rock and back to melted rock, usually takes millions of years. You will never see it happen, but it is happening under your feet right now.

**Recap.** Rock never stops changing: it weathers, presses, heats, and melts its way around the rock cycle, forever.

## Practice

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

## Needs first

- [Earth's Layers](https://lightmysky.com/learn/science/earths-layers-mt_jwElFY7Syd)
- [Types of Rock](https://lightmysky.com/learn/science/types-of-rock-mt_NYA50DFcOO)
- [Erosion and weathering](https://lightmysky.com/learn/science/erosion-and-weathering-mt_vAP_A986IQ)

## Opens up

- [Volcanoes & Mass Extinctions](https://lightmysky.com/learn/science/volcanoes-and-mass-extinctions-mt_QwWo6an9N1)
- [The Rock Cycle](https://lightmysky.com/learn/science/the-rock-cycle-mt_NckKLZ3uCE)