Experiment Physical Weathering

Download printable Experiment Sheet here.

Physical, or mechanical, weathering is the process by which rocks break apart due to their physical interaction between the rocks and their environment. Water, wind, ice and other rocks... even people... can weather rocks by mechanical actions. Physical weathering contains several processes - thermal expansion, frost wedging, exfoliation, abrasion, and salt crystal growth. Each of these results in the breakdown of rock into smaller sediments. 

In this experiment we will demonstrate the breakdown via abrasion. Rocks are constantly ground down by the effects of water, wind and ice rubbing rocks together. As this occurs with time, they break down through the constant action of the elements. Here, we will use chalk to simulate the break down of rocks by abrasion.

Materials:

Jar
Rock Salt
Colored Chalk

  1. Add rock salt to jar, and a piece of the chalk to a jar and put the lid on.
  2. Shake, shake, SHAKE!!!
  3. Pour out the contents and observe. They have broken into smaller pieces.
  4. Return the lid and repeat several times and view how the sediment sizes get finer grained each time.

Questions to consider:

  • How is the chalk different after shaking? The more you shake do grains get larger or smaller?
  • How is the salt different after shaking?
  • How do you think something similar would happen in nature?

 

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