Break a Rock!
In-Class Activity 1_Weathering and Soils
Julia Kahmann-Robinson PhD and Marjorie Chan PhD, University of Utah Department of Geology & Geophysics
Determine how the physical breakdown of rocks leads to increased rates of weathering and erosion.
Depending on class size the following is needed for each student or team of students:
- Rock hammers
- Rocks (Geodes would be nice! Otherwise, a rock with a weathering rind is good).
- Hand lens if possible, but not necessary
Use the rock hammer and rock provided by your instructor. Break the rock in such a manner that you can see "the middle" of the rock
ExploreHave students make a sketch in each circle below of the outside vs. inside of the rock (respectively). Students should note color changes, sizes of crystals, any mottling etc., and be as observant as possible. Also, they should provide some sort of scale to understand the relative sizes of your sketches.
Mechanical vs. Chemical Weathering
Consider the sketches, do students see evidence for mechanical weathering and/or chemical weathering? Please list them.
- The rates of weathering depend on a number of factors, from climate to grain size of the weathered lithology. Help students to recognize these different factors and perhaps what is most influential
- Have students try to recognize weathered vs. non-weathered material and how it appears in hand sample. Use a hand lens is possible.
- Are there different rates or rock responses to weathering in the picture below? What parts are resistant to weathering and why? Note the scale in the caption.
- Have students find an internet image of the weathered accumulations of these "blueberries" from other Opportunity explorations and explain what that that means about how an outcrop would erode over time.
Ask students to list the most important factors in the rate of weathering (name 3 factors).