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Weathering The breakdown do the materials of Earths crust into smaller pieces. Slide 2 Mechanical Weathering Slide 3 Photo A Photo B What has caused these stones to become smooth? Slide 4 Photo A Photo B Abrasion by water (a type of Mechanical weathering) Slide 5 Abrasion The grinding and wearing away of rock surfaces through the mechanical action of other rock or sand particles. Caused by wind, water, & gravity. Slide 6 http://geology.com/rock-tumbler/rock- tumbler-grit.shtml Slide 7 TUMBLING GRIT: Silicon Carbonate is harder than the rocks you are tumbling and will therefore smooth off the rough edges. This is used to smooth the rocks out. As these tiny rocks hit the larger rocks and are tumbled together, it makes the rocks smooth and round. Slide 8 http://geology.com/rock-tumbler/rock- tumbler-grit.shtml Rocks before they are tumbled.. And after they are tumbled. The Tumbling causing abrasion to happen. Slide 9 Sea glass Slide 10 Sea glass starts out as broken glass. Slide 11 Water causes abrasion of the sea glass as the water causes the sand and glass to tumble against each other. Slide 12 Sea glass: now the glass is smooth and round because of the abrasion of sand against the glass. Slide 13 How did the pebbles get this way? Why are they not sharp? Slide 14 Answer: Abrasion Slide 15 Flowing Water As rocks and pebbles roll along the bottom of flowing water, they bump and scrape against each other, causing these rocks to become rounded and smooth. Slide 16 2. Water River carries rocks and pebbles that bump and scrape against each other, eventually wearing them down. (This makes them smooth & rounded). Slide 17 National Geographic Photos A. What type of weathering causes this? B.What agent? Slide 18 National Geographic Photos A. Mechanical weathering B. Wind blowing sand against the rock, causing abrasion Slide 19 WIND wind blows sand and silt against exposed rock eventually wearing away the rocks surface. Slide 20 http://www.cbc.ca/news/canada/british-columbia/story/2008/07/30/bc-highway-rockslide-whistler.html A. What type of weathering causes this? B.What agent? Slide 21 http://www.cbc.ca/news/canada/british-columbia/story/2008/07/30/bc-highway-rockslide-whistler.html A. Mechanical weathering B. Gravity, which causes rocks to tumble Into each other as they fall, which breaks them apart more by abrasion Slide 22 http://www.cbc.ca/news/canada/british-columbia/story/2008/07/30/bc-highway-rockslide-whistler.html Slide 23 GRAVITY Rocks grind against each other during a rock slide, creating smaller and smaller rock fragments. Anytime one rock hits another rock, abrasion takes place. Slide 24 What type of weathering is this? What agent causes this? Slide 25 Mechanical weathering: ice wedging Slide 26 ICE Water seeps into cracks during warm weather. When the temperature drops, the water freezes and expands, causing the ice to push against the sides of the crack. * This causes the crack in the rock to widen. Slide 27 PLANTS The roots grow through existing cracks in rocks. The growth causes the root to expand, forcing the crack to widen. The force can eventually split the rock apart. Slide 28 6. Animals Burrowing animals loosen sediment & push it to the surface. This exposes it to other forces of weathering. Ex. Rabbits, worms, ants, coyotes, & mice Slide 29 Animals Animals that live in the soil (moles, prairie dogs, insects, worms, gophers), cause a lot of weathering. By burrowing in the ground, these living creatures brake up soil and loosen rocks to be exposed to further weathering Slide 30 Question Time 1. For each question, tell what type of mechanical weathering is happening. 2. Write on dry erase board the agent causing the weathering. 3. Discuss with your partner & explain how that agent caused what you see in the picture. Slide 31 What agent of mechanical weathering is at work here? Slide 32 Flowing Water As rocks and pebbles roll along the bottom of flowing water, they bump and scrape against each other, causing these rocks to become rounded and smooth. Slide 33 What agent of mechanical weathering is at work here? Slide 34 WIND wind blows sand and silt against exposed rock eventually wearing away the rocks surface. Slide 35 What agent of mechanical weathering is at work here? Slide 36 Slide 37 Slide 38 ICE Water seeps into cracks during warm weather. When the temperature drops, the water freezes and expands, causing the ice to push against the sides of the crack. This causes the crack in the rock to widen. Slide 39 Ice- Wedging Slide 40 What agent of mechanical weathering is at work here? Slide 41 Animals Animals that live in the soil (moles, prairie dogs, insects, worms, gophers), cause a lot of weathering. By burrowing in the ground, these living creatures brake up soil and loosen rocks to be exposed to further weathering Slide 42 Animals Slide 43 What agent is at work here? What type of weathering? Slide 44 Mechanical weathering Tree roots Slide 45 PLANTS The roots grow through existing cracks in rocks. The growth causes the root to expand, forcing the crack to widen. The force can eventually split the rock apart. Slide 46 Temperature Change Cold causes rock to contract (shrink). Heat causes rock to expand (grow slightly). Slide 47 CHEMICAL WEATHERING Process by which rocks break down as a result of chemical reactions. Slide 48 CHEMICAL WEATHERING chemical reactions Process by which rocks break down as a result of chemical reactions. Dissolve minerals in rocks or change them into different minerals. Slide 49 Agents of chemical weathering 1. Water 2. weak acids (acid precipitation, acids in ground water, acids in living things) 3. air. These agents weaken bonds between the mineral grains of rock. Slide 50 Water Can cause rock to be broken down and dissolve. Can take thousands of years to take place. Slide 51 1. Water Dissolves minerals from a rock over a long period of time (sometimes 1000s of years). Slide 52 2. Weak Acids Include 1.acid precipitation 2.acids in ground water 3.acids in living things Slide 53 2. Acid precipitation Where does acid rain come from? Rain, sleet, or snow, that contains a high concentration of acids. Small amounts of nitric or sulfuric acids from volcanoes. Air pollution from fossil fuels (coal & oil) give off gases & combines with water to form acid rain. Slide 54 Acid Precipitation ( weak acid) Rain, sleet, or snow that contains a high concentration of acid. Normal precipitation is acidic, acid precipitation contains more acid than normal. Slide 55 Acid Rain Compounds from burning coal, oil and gas react chemically with water forming acids. Acid rain causes very rapid chemical weathering Slide 56 3. Acids in Ground water Some groundwater contains weak acids like carbonic & sulfuric acid. These weak acids react with rocks, causing a chemical reaction. Ex. When groundwater touches limestone, it dissolves limestone to form caves over thousands of years. Slide 57 Acids in Groundwater (weak acid) Carbonic acid or sulfuric acid reacts with rocks in the ground, causing a chemical reaction, eating away at the rock. Slide 58 Karst Topography A type of landscape in rainy regions where there is limestone near the surface, characterized by caves, sinkholes, and disappearing streams. Created by chemical weathering of limestone Slide 59 Features of Karst: Sinkholes Slide 60 Features of Karst: Caves Slide 61 Features of Karst: Disappearing Streams Slide 62 National Geographic Photos What type of weathering are these lichens causing on the rock? What agent of weathering ? Slide 63 National Geographic Photos Mechanical weathering Agent: acids in living things (they dissolve the minerals in the rock) Slide 64 Acids in Living Things (weak acid) Lichens produce acids that slowly break down rock. Slide 65 4. Acids in Living things Lichens produce acids that slowly break down rock Roots and decaying plants release acids that dissolve minerals, thus weakening the rock. Slide 66 Slide 67 AIR The process of oxidation is a chemical reaction in which an element (iron) combines with oxygen, causing rust. Slide 68 5. Air oxidation Oxygen in the air reacts with iron, causing it to rust. This process is called oxidation. A chemical reaction in which an element (iron) combines with oxygen to cause rust. Causes aluminum cans, bikes, & cars to rust. Water speeds up this process. Slide 69 What type of weathering is happening here? What agent is at work ? Slide 70 Chemical Weathering Water dissolves the minerals in the rock Slide 71 Water Can cause rock to be broken down and dissolve. Can take thousands of years to take place. Slide 72 What type of weathering caused the changes to this statue? What agent is at work? Slide 73 Chemical weathering acid precipitation Slide 74 Acid Precipitation ( weak acid) Rain, sleet, or snow that contains a high concentration of acid. Normal precipitation is acidic, acid precipitation contains more acid than normal. Slide 75 What type of weathering is at work here? What agent created the cave? Slide 76 Chemical weathering Acids in groundwater Slide 77 Acids in Groundwater (weak acid) Carbonic acid or sulfuric acid reacts with rocks in the ground, causing a chemical reaction, eating away at the rock. Slide 78 What type of weathering caused this? What agent? Slide 79 Sinkholes caused by chemical weathering. Agent: acids in groundwater Slide 80 What type of weathering and what type of agent has caused the rust on these metal objects? Slide 81 Chemical weathering Agent: air. Oxygen in the air causes oxidation, which causes rust. Slide 82 What type of weathering caused this rock to split in half? What agent of weathering? Slide 83 Mechanical Weathering Agent: Ice wedging Water gets into the crack, freezes, and expands, pushing the rock apart. When the water thaws (melts) and then freezes and does this over and over again, it causes the rock to break apart. Slide 84 What type of weathering caused this statue to become worn down? What agent of weathering? Slide 85 Mechanical Weathering Wind Wind blows sand against the statue, causing abrasion. Remember, sand is just broken down rocks and minerals.