“MECHANICAL WEATHERING” 
STUDENT ORGANIZER ANSWER KEY

1. What is the force behind weathering by exfoliation? (As surface layers of rock erode, pressure on the layers beneath is “unloaded,” and the lower levels expand upward and outward, resulting in the cracking and “peeling” of surface layers.)
1a. Where is it most likely to occur? (Mountain ranges.)
2. What is the force behind weathering by Thermal Expansion and Contraction? (Rock crystals crack during cycles of expansion and contraction corresponding to exteme heat and cold.)  
2a.Where is it most likely to occur? (Deserts.)
3. What is the force behind weathering by Crystal Growth? (Growth of salt crystals in spaces between rocks.)  
3a. Where is it most likely to occur? (Coastal areas and deserts.)
4. What is the force behind weathering by Tree Roots? (Tree roots grow into and expand cracks in the rocks.)
4a.Where is it most likely to occur? (Any rocky area able to support tree growth.)
5. What is the force behind weathering by Abrasion? (Particles of sediment wearing against rock.) 
5a. Where is it most likely to occur? (Anywhere, although most pronouncedly in harsh environments.)  
5b. What else do you think might abrade rock besides sediments? (Human and animal activity.)