WATER S EFFECT EARTH S 10.4

Transcription

1 WATER S EFFECT ON SHAPING EARTH S SURFACE 10.4

2 OBJECTIVES Water is always on the move through the water cycle Explain that no matter what form water is in, it has the ability to reshape the surface of the earth List the different ways water can reshape the surface of the earth Describe the two main processes in which water breaks down Earth s landscape Describe what deposition is and how water builds up on features of the landscape

3 KEY TERMS Cave Delta Deposition Erosion Karst Landslide Rapids Striations Weathering (chemical, physical, biological)

4 INTRODUCTION It is hard to believe that snow falling down onto the surface of a rock can shape it. While one snowflake will not do this all by itself, many of them combined will over many centuries If there is enough buildup of snow and ice and they begin to melt and slide down the surface of a rock, they will scrape away, tear, crack, and carry away rock Imagine sandpaper over rock

5 INTRODUCTION While the formation of ice and snow as a glacier melting takes hundreds if not thousands of years, there are faster ways to shape the landscape with water in its liquid form For example, a flash flood or landslide can immediately change the shape of the Earth s surface Or another example over millions of years like the grand canyon

6 WEATHERING, EROSION, AND DEPOSITION Water helps in the weathering, erosion and deposition processes Solid as a rock expression always changing wind, volcanoes, earthquakes, water

7 WEATHERING Weathering is the process in which breaking down rock into smaller pieces or fragments There are two types of weathering Physical weathering (aka mechanical) is when rocks are broken down by force, but still remain as the same kind of rocks Chemical weathering where rocks are broken down by chemicals into different types of matter Rope Swing Vid

8 WEATHERING PHYSICAL Physical weathering is when the rock is scratched, scraped and broken into smaller pieces and the composition or what is it made up of does not change This is done by rocks being scraped by harder rocks and breaking down Occurs most quickly where the climate includes high levels of precipitation and large temperature changes (between night and day, and also from season to season) Ice wedging (aka frost wedging) weathers rocks due to the expansion of water as it freezes Most common in BC

9 WEATHERING - CHEMICAL Chemical weathering is a chemical reaction that causes rocks to break down, or decompose. When a chemical reaction occurs, the minerals in the rocks change their composition and the rock becomes weaker. Occurs most quickly where climate is warm, there is high levels of rainfall and pollution Water + oxygen = much chemical weathering, including rusting aka oxidation

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11 WEATHERING - CHEMICAL Chemical weathering also occurs underground Carbon dioxide is the gas released by living things through respiration. When rainwater mixes with CO2 in the atmosphere or carbon from organic materials on the ground, the water droplets become acidic, meaning they form a mild acid called carbonic acid Carbonic acid + Calcium carbonate baking soda and vinegar

12 WEATHERING - CHEMICAL Little by little as these small gaps are eaten away into rocks forming caves, sinkholes and karsts Much of our rock is made up of limestone which reacts well with the carbonic acid

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14 WEATHERING BIOLOGICAL Biological chemical weathering occurs if physical or chemical weathering has been caused by a plant or animal the process is sometimes referred to as biological weathering

15 EROSION BY WATER Erosion by water Moving water breaks down rock into sediment Sediment can be eroded far away and deposited V-shaped valleys are carved by flowing water Rapids create more weathering as water moves faster Ocean waves continually erode shoreline Gravity can cause landslides and avalanches

16 EROSION BY ICE Erosion by ice Glaciers once covered all of BC (2 km deep, years ago) leave striations (scratch marks) on rocks form U-shaped valleys can move large rocks long distances

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19 EROSION BY ICE After erosion, sediments are eventually deposited A delta forms where a river empties into a calm basin Glaciers deposit many different forms of sediment

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21 VIDEOS Grand Canyon Glaciers Glace Ciiers Largest Ice Body