WEATHERING
Chemical and/or Physical breakdown of rock Definition Chemical and/or Physical breakdown of rock
Physical Weathering breakdown of rock into smaller pieces (mechanical) Does not involve a chemical change in the rock
Frost Action/Wedging alternate freezing and thawing due to the expansion of water when freezes = potholes
b. Abrasion Rounding of rocks due to the rocks hitting each other
c. Root Action Roots wedge and grow in rocks
d. Exfoliation Large sheets of loosened rock peel away
Chemical Weathering Breakdown of rock due to a chemical change in the rock Often requires water The higher the temperature, the faster the chemical weathering
a. Oxidation Iron + Oxygen iron oxide, (commonly called rust)
b. Carbonation Carbon dioxide + water = carbonic acid (in rain) – a weak acid Slowly dissolves Limestone and Marble
Karst Topography Caves and Sinkholes
http://www.youtube.com/watch?v=tQvv8YFCGsY Karst and corvettes http://blog.hemmings.com/index.php/2014/02/12/breaking-news-eight-cars-damaged-by-sinkhole-at-the-national-corvette-museum/?refer=news
c. Hydration Water plus other minerals Ex. Feldspar + water will slowly change into clay
Factors that Affect Weathering
1. Particle Size/Surface Area exposed at Surface The more surface area exposed, the ________ the weathering quicker
Which will weather faster and why? Why will smaller particles weather faster? Surface Area and Weathering Which will weather faster and why? Pebbles Sand Silt Clay because it is the smallest
2. Mineral Composition The harder the rock, the longer it takes to break down b. Calcite/Limestone >> dissolves in acidic water
Which layer, X or Y is more resistant to weathering? Y, is hasn’t weathered as much
3. Climate Chemical Weathering Physical Weathering A. Warm, moist climate >>> B. Moist with temperature variations of freezing and thawing >>> Chemical Weathering Physical Weathering