Weathering

Weathering –breaking down and changing the rocks on Earth’s surface 2 main types

1) Mechanical weathering rocks and minerals breaking down without changing their chemical composition

Factors of Mechanical Weathering A. Temperature When water freezes it expands by 9% If water collects in spaces in rocks and freezes it can cause them to split This is called frost wedging

B. Pressure Buried rocks have a lot of pressure on them As rocks get closer to the surface, there is less pressure With less pressure, rocks can expand and crack

2) Chemical weathering rocks and minerals undergo changes due to chemical reactions

Agents of Chemical Weathering A. Water Water can dissolve many minerals and rocks

B. Carbon Dioxide Carbon dioxide reacts with water to form carbonic acid Carbonic acid can dissolve rock

C. Oxygen Oxygen will react with many substances These reactions are called oxidation Ex. Iron oxidation – rust formation

Caused by human activities (pollution) D. Acid precipitation Caused by human activities (pollution) Sulfuric acid – burning coal Nitric acids – car exhaust cause other problems as well

What affects rates of weathering? Climate High chemical weathering in warm, moist climates High mechanical in cool, dry climates

Rock type and composition Igneous resist weathering Sedimentary would be most vulnerable Surface area More rock above ground = more rock exposed to weathering Topography Level areas weather less than slopes