Lesson 9 — Changing Earth's Surface: Weathering 1 / 5

Earth's surface is always changing — usually so slowly we cannot see it happening. Today we find out how rocks get broken down. 🪨

Step 1: Weathering is when rock is broken into smaller pieces where it is. There are three types.

Today we will meet all three: mechanical, chemical and biological.

Step 2: Mechanical weathering physically breaks the rock — without changing what it is made of.

ice freezes and widens the crack

The best example is freeze and thaw: water gets into a crack, freezes, and pushes the crack wider. Over and over, until the rock splits.

Step 3: Two more types of weathering.

🧪 Chemical weathering
A chemical reaction breaks the rock down — like acid rain slowly dissolving limestone.

🌱 Biological weathering
Living things break the rock — like tree roots cracking a path, or people mining.

Your turn to be a weathering detective! 🔎

  1. Do the vocabulary match-up in your group.
  2. Go on the weathering hunt around school and find examples.
  3. Complete the Weathering Detectives worksheet.

Remember: mechanical = broken by force; chemical = broken by a reaction; biological = broken by living things.