WEATHERING AND EROSION WEATHERING AND EROSION Questions: What is meant by weathering? How does weathering happen? What areas tend to have more weather occurring in the United States?

Weathering occurs when rocks are exposed to: 1. Atmosphere2. Hydrosphere3. Living things 1. What is weathering? Weathering- is the process that breaks down rock and other substances at Earth’s surface. 2. What contributes to weathering? Heat, cold, water and ice all contribute to weathering.

3. What is erosion? Erosion is the removal of rock particles by wind, water, ice or gravity. 4. What does weathering and erosion do? Weathering and erosion work together continuously to wear down and carry away the rocks at Earth’s surface. 5. What is Uniformitarianism? Uniformitarianism states that the same process that operate today operated in the past. 6. What are the two kinds of weathering? The two kinds of weathering are mechanical weathering and chemical weathering.

6. There are two kinds of weathering: lThe two kinds of weathering are: mechanical weathering and chemical weathering.

7. What is mechanical weathering ? EXAMPLES: Mechanical weathering is the type of weathering in which rock is physically broken into smaller pieces. a) Plant Growth/Root Action: Plant roots grow through cracks and break the rock.

b)Freezing and Thawing/ Frost Action water freezes and expands in cracks. As this happens over and over again the rock breaks. c) Release of Pressure/Exfoliation: Changes in temperature cause the rock to expand and contract.

d) Abrasion: When rocks or sediments rub against another rock ex: sandblasting

e. Animal Actions Animal actions that burrow in the ground including moles, gophers, prairie dogs, and some insects – loosen and break apart rocks in the soil.

Mechanical or Physical Weathering

EXAMPLES: 9. What is chemical weathering? Chemical – is the process that breaks down rock through chemical changes. a ) Oxidation - When elements in the rock react with O 2 (oxygen) Fe (iron) + O 2 (oxygen) = | Fe 2 O 2 (iron oxide or rust) 10. What causes chemical weathering? The causes of chemical weathering include the action of water, oxygen, carbon dioxide, living organisms and acid rain.

b) HYDRATION- When elements in the rock react with H 2 O (water- the “ universal dissolver ” ) Feldspar (common mineral) + H 2 O = Clay Clay = fine particles that are usually wet

c) CARBONATION- When elements are dissolved by acid rain. Carbon Dioxide + Water = Carbonic Acid or Sulfur Dioxide + Water = Sulfuric acid Example: Marble grave stone dissolved by acid rain

d. Living Organisms – as the plant’s roots grow, they produce weak acids that slowly dissolve rock around the roots. Lichens-plantlike organisms that grow on rocks-also produce weak acids that chemically weather rock. e. Acid Rain – burning large amounts of coal, oil, and gas for energy. Burning these fuels can pollute the air with sulfur, carbon, and nitrogen compounds. Such compounds react chemically with the water vapor in clouds, forming acids. These acids mix with raindrops and fall as acid rain.

Chemical Weathering

FACTORS AFFECTING THE RATE AND TYPE OF WEATHERING 1. EXPOSURE- more exposure to air, water and living things the faster the weathering Therefore, rocks near the surface are weathered and rocks deep under ground are not DEPTH RATE OF WEATHERING RATE OF WEATHERING

2. PARTICLE SIZE- The smaller the particle size, the greater the total surface area that is exposed to weathering. SAME OVER ALL VOLUME MORE EXPOSED AREA PARTICLE SIZE RATE OF WEATHERING RATE OF WEATHERING

3. Mineral Composition - Different minerals have different resistances to weathering. EXAMPLES: Quartz is hard, takes a long time to weather. Talc is soft, takes a short time to weather. MINERAL HARDNESS MINERAL HARDNESS RATE OF WEATHERING RATE OF WEATHERING

Cold climates frost action most effective form of weathering. 4. Climate - In warm, moist climates chemical weathering is dominant. In dry climates very little weathering happens. A lot of freezing and thawing - frost action is the most effective form of weathering TEMPERATURE RATE OF PHYSICAL WEATHERING RATE OF PHYSICAL WEATHERING TEMP. AND MOISTURE TEMP. AND MOISTURE RATE OF CHEMICAL WEATHERING RATE OF CHEMICAL WEATHERING

PRODUCTS OF WEATHERING 3. Ions - Particles dissolved in water (salty oceans) Weathering results in four types of sediment: 1. Solid sediment - sand and pebbles. 2. Colloids clay sized particles (small sediment) 4. Soil - a mixture of sediment and organic matter