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Science 7.1
Weathering and Erosion
| Question | Answer |
|---|---|
| What causes potholes in roads? | Frost Wedging during winter months. |
| Define weathering. | Process by which rocks on or near earth surface break down and change |
| Define erosion. | Removal and transport of weathered material from one location to another |
| What are the two types of weathering? | Mechanical and Chemical. |
| What is mechanical weathering? | Process by which minerals break down into smaller pieces. Also called physical weathering. Does NOT change chemical composition of rock |
| What role does water play in mechanical weathering? | Freezes and expands, increasing in volume by 9%.Exerts pressure on rock and widens a crack. Water flows into crack, freezes, and widens it even more |
| What is frost wedging? | Repeating thawing and freezing of water in the cracks of rocks. |
| How does pressure affect mechanical weathering? | Bedrock is deep and under great pressure. When overlying rock is removed, bedrock is able to expand and form long curved cracks called joints that occur parallel to rock surface. |
| How do plants affect mechanical weathering? | They can wedge into the cracks of rocks, when root grow they extert pressure and widen/crack rock. |
| What is chemical weathering? | Process by which rocks and minerals undergo changes in their composition as the result of chemical reactions. With all else equal, rate of reactions double with each 10 degrees Celsius |
| What is exfoliation? | Process by which outer rock layers are stripped away (similar to onion being peeled) |
| What can reduced pressure in deep mines result in? | It can result in large pieces of rock exploding off of the mine walls. |
| What are two factors that affect chemical weathering? | 1. The composition of the rock 2. The environmental temperature |
| How does water affect chemical weathering? | Can dissolve many minerals and rocks, and serve for a medium for other reactions to occur |
| What is oxidation? | The chemical reaction of oxygen with other substances. |
| What minerals are often affected by oxidation? | Magnetite, Hornblende, Biotite, and Pyrite. |
| How does CO2 affect chemical weathering? | CO2 (produced by organisms during repiration) combines with water and forms weak carbonic acid that falls to Earths surface as precipitation (acid rain) |
| How does carbonic acid affect calcite and marble? | It dissolves limestone and marble |
| How does carbonic acid affect silica? | It forms clay when reacting with silicates |
| How does decaying organic matter and plant respiration affect the amount of carbonic acid? | Deaying matter and respiration form high CO2 levels with react with ground water to form high levels of carbonic acid |
| What is acid precipitation? | acid rain, snow, sleet, or hail |
| Give two ways acid precipitation can form. | 1. Sulfur dioxide from industrial fossil fuels conbine with water and from sulfuric acid 2. Nirogen oxides from motor vehicle exausts combine with water to form nitric acid |
| Describe the pH scale. | Shows how "Acidic " solution is. Runs from 0-14. Water is in the middle (pH 7). The lower the number, the stronger the acid. Anything above ph7 is called a "base" |
| When the pH of freshwater is not in the range of 6-8, what can occur? | This can adverselt affect fish, aquatic plants and ampibians. THe diversity of species can decrease. |
| With natural weathering, what is an average rate for limestone? | 2000 years to weather 1 cm of limestone |
| What four variables can affect the rate of weathering? | 1. Climate 2. Rock type and composition 3. Rock surface area 4. Topography |
| What climate conditions increase the rate of physical weathering? | COol and dry climates, especially high climates that promote frost weathering |
| What climate conditions are not favorable for chemical weathering? | Cool climates where water is is usually frozen all year |
| How does rock type and composition affect the rate of weathering? | Rocks that are harder and resistant to breaking are less affected by weathering. Sedimentary rocks are more easily weathered that igneous and metamorphic. |
| How does rock surface area affect the rate of weathering? | The greater the exposed surface area, the more easily it will be broken down |
| How does topography affect the rate of weathering? | Topography refers to elevation. Gravity will pull down weathered fragments easier on hilly areas as opposed to flat land. This will allow newly exposed surfaces to begin weathering. |
| How do organisms affect the rate of weathering? | Decaying organic matter and plant roots release CO2 which combines with water, produced carbonic acid, and increases weathering rate. |
| What climate conditions increase the rate of chemical weathering? | 1. Abundant rainfall 2. Warm temperatures 3. Lush vegetation. These factors allow rich organic matter and lots of water to form high carbonic acid levels. |
| List four agents of chemical weathering. | 1. Water 2. Oxygen 3. Carbon Dioxide 4. Acids |
| What is hydrolysis and when does it occur? | Reaction of water with other substances. Occurs in decomposition of silicate materials. (potassium feldspar decomposes into kaolinite) |
| How does oxygen affect chemical weathering? | Combines with other substances |
Created by:
nlomis
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