How Do Rocks Break?

Contributor: Hannah Brooks. Lesson ID: 12443

Have you ever played "rock, paper, scissors" to choose sides? Rock breaks scissors, but what breaks rock? Earth has different and surprising ways to break and change rocks throughout the "rock cycle"!


Earth Science

learning style
personality style
Grade Level
Intermediate (3-5), Middle School (6-8)
Lesson Type
Dig Deeper

Lesson Plan - Get It!


What do you think it would take to break this large boulder? What if you blow on it or spray it with a hose for, say, hundreds of years? Grow . . . bolder . . . in your knowledge of rocks and minerals!

Rocks of any size can be broken down into smaller pieces through different geologic processes.

If you missed, or would like a review on the first lesson in the Rocks and Minerals series, check it out in the right-hand sidebar under Related Lessons.

What do you think is the result of rocks being weathered and broken down? Weathering and breaking causes rocks to change into another type of rock through the rock cycle.


Rocks are broken into smaller pieces during the process of weathering. Weathering can occur because of physical, organic, or chemical causes. Take a sheet of paper and tear it in half. You just physically, or mechanically, "weathered" the piece of paper. You changed the appearance without changing the overall makeup of the paper.

Mechanical, or physical, weathering often involves water acting as an agent of change. Did you know that water expands when it freezes? Water moves into small cracks of rock and expands when it freezes. That pushes the rock apart, slowly breaking it down into smaller pieces.

crack in foundation

Water can also wear down the surface of the rock, pulling small pieces off over time.

rock in a river

Organisms can organically break down rocks by pushing roots downward through the soil. Roots push rocks apart and release chemicals that slowly dissolve the rock material. This is called organic weathering, because it involves living organisms.

root growing into brick

Chemical weathering involves materials actually changing the makeup of the rock. Take a spoonful of sugar and dissolve it into warm water. You just combined sugar and water into a solution. Water and other substances can dissolve chemicals from rocks, causing them to break down into smaller pieces.

weathered sandstone

Once the rock is broken down into smaller pieces, it is able to be moved to a new location. Rocks can be broken down through physical, organic, and chemical weathering processes. Physical weathering changes the appearance of rocks, while organic and chemical weathering can actually change the composition of the rock.

Write a short paragraph about the three types of weathering to summarize what you learned. Share your paragraph with a parent or teacher before moving to the Got It? section, where you will learn how weathering and erosion are different.

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