Grade 5 Hands on Science Weathering, Erosion and Deposition

Transcription

1 Grade 5 Hands on Science Weathering, Erosion and Deposition Objective: To demonstrate and investigate the effect of weathering, water and wind erosion and the subsequent deposition into landforms. Background: The Earth's surface is constantly being shaped and reshaped by natural processes. Some of these process are rapid and dramatic like earthquakes and volcanoes, while others are slower and more subtle like those processes involving wind, water and ice. The types of landforms that are produced in a given area depends on a variety of factors: structure (what materials the landforms is made of rock? soil? sand?): rock: igneous rock (formed from the cooling and solidification of magma or lava, very hard and therefore more resistant to weathering and erosion) metamorphic rock (formed from heat and pressure that result in physical and chemical changes in rocks) sedimentary rock (formed from the deposition and cementing together of sediment particles over time, more sensitive to weathering and erosion) soil/sand: landforms made of soil/sand/silt/gravel etc. are more prone to changes then rock gravel and sand (especially when dry) are more likely to be affected soil and humus are moderately likely to be affected clay and silt are the least likely to be affected as compared to other soil/sand landforms process of formation (the forces that are involved in the formation of the landforms: weather, water, wind, moving sheets of ice, temperature, tree roots etc) slope (how steep the landforms is) drainage (how quickly water drains away from a landform) Examples of Landforms: mountain ranges (very tall landforms, much higher than a hill) valleys (a low place between mountains) plateaus (a large, flat area of land that is higher than the surrounding land) plains (flat lands that have only small changes in elevation) peninsula (a body of land that is surrounded by water on three sides) isthmus (a narrow strip of land with sea on either side, forming a link between two larger areas of land) island (a piece of land that is surrounded by water) canyons (a deep valley with very steep sides - often carved through the Earth by a river) Mountains form from movement of the Earth's tectonic plates (and the subsequent earthquakes and volcanoes), and other landforms are the result of weathering (the process where rocks are worn away or broken down into smaller pieces), erosion (the process of moving sediment from one place to another) and deposition (the process of dropping off or depositing sediment in a new location). Erosion can be caused by a variety of things, for example: Gravity can cause landslides.

2 Wind can result in the formation and ever changing nature of sand dunes. Glacier movement causes the formation of U-shaped valleys. Flowing water can form canyons, sink holes. and waterfalls. Activities of people and animals (such as building dams for example) can also affect landforms. Deposition result in the formation of a variety of landforms, for example: beaches - movement of water deltas - movement of wind sand dunes - movement of ice/glaciers stalactites/stalagmites - accumulation of mineral deposits built from dripping water In summary: Weathering results in the production of sediment as a particular landform is broken down. This sediment is moved to a new location through the process of erosion and it is set down or distributed in this new location in a process known as deposition. As a result, landforms on earth are constantly changing. Part 1: Weathering Objective: to demonstrate the process of mechanical and chemical weathering. You will be provided with: a cup with sugar cubes, vinegar, a eye dropper and a graham cracker Background: Weathering, the process where rock is dissolved, worn away or broken down into smaller and smaller pieces. Weathering can occur due to mechanical, chemical or organic weathering processes. Mechanical weathering - a process that causes a physical disintegration of exposed rock without any change in the chemical composition of the rock. example: Water flows into a crack in a rock. As it freezes it expands and widens the crack. Eventually the rock will break. Organic weathering - example: Tree roots grow into a crack in a rock. As the root grows it exerts pressure on the rock and widens the crack. Eventually the rock will break. Chemical weathering - a process that causes the rock to undergo a chemical reaction that allows the rock to become a different kind of rock, often one that is soluble in water. example: Acid rain washes over a stature. Over many years layers of the statue dissolves and washes away. Take 1 sugar cube. Apply weight to the sugar cube until it breaks. Continue breaking the cube into sediment. This is an example of mechanical weathering. Take the cup with the remainder of the sugar cubes. Place the graham cracker over top of the sugar cubes. The cracker represents the soil overlying a limestone (sugar cube) foundation. Using the eyedropper, slowly drop by drop, add vinegar to the cracker. Try to keep the drops on the cracker. Continue until the cracker is soggy and almost falling apart. Remove the cracker and observe what the sugar cubes now look like.

3 What do you observe? (You will see an empty pocket where the vinegar has dissolved the sugar cubes under our cracker.) This is an example of chemical weathering. This represents the way that caverns and sinkhole form. Part 2: Wind Erosion Objective: to demonstrate and investigate the effect of wind on landforms. You will be provided with: a straw for each student, aluminum pans filled with dry sand, rocks, stream table filled with wet sand, coffee stir stick "trees", a small potted plant In the aluminum trays filled with dry sand: GENTLY blow on the dry sand in the aluminum pans. See if you can make a hill or a valley using wind. Mound the sand into a hill and a valley with your hand or a spoon. Blow onto these to see how they are affected by wind. Put a rock in the sand. Can you blow the sand away from the rock? Place several stir stick "trees" in the sand. Try to blow sand away from the "roots" of your "trees". Record your observations. In the stream tables filled with wet sand: Blow on the wet sand in the stream tables. See if you can make a hill or a valley using wind. Mound the sand into a hill and a valley with your hand. or a spoon Blow onto these to see how they are affected by wind. Put a rock in the soil. Can you blow the soil away from the rock? Place several stir stick "trees" in the sand. Try to blow sand away from the :roots" of your "trees". Record your observations. Take the small potted plant and attempt to blow dirt away from the roots of the plant. Were you successful? Why is this important in regards to erosion in the environment? Throw away the used straws. Discussion: ask: Was it easier to blow the wet or dry sand? (Dry) ask: What was the effect of adding rocks or trees on your ability to move the sand? (The presence of these items interfered with the movement of the sand). ask: Why is soil erosion a problem? (farmers lose top soil, streams and rivers get clogged, wildlife lose habitats, particles in the air cause respiratory issues) ask: Why is sand erosion a problem? (expensive beaches wash away, sand is abrasive to windows and automobiles, sand can clog streams and rivers)

4 ask: What can people do the prevent or slow erosion? (Growing plants because plant roots hold onto the soil, keeping the soil wet in dry climates, building fences or planting rows of trees to block the wind).

5 Part 3: Water Erosion Objective: to demonstrate and investigate the effect of water on landforms. What you will be provided with: stream tray filled with wet sand, shells, rock. coffee stir stick "trees", water, plastic cups with holes on the bottom, plastic spoons, funnel BE SURE THAT THE RUBBER DRAIN IS OVER THE BUCKET! DO NOT REMOVE THE FILTER PAPER FROM THE BOTTOM OF THE TRAY! Set up the sand in your stream table to slope like the side of a mountain. Use the rocks, shells and stir sticks to represent trees, buildings, and boulders. Draw the setup of your mountain in the student handout. Have one student slowly and carefully, pour water on the top of the stream table through the plastic cups (resting on the wooden platform) to simulate rain. Draw how your mountainside has changed in the student handout. Have each student place a grain of rice on the top of their mountain. Repeat the previous step and have the students watch the movement of the grain of rice as a result of the flow of water. ask" What does the movement of the rice tell you about the movement of sediment during water erosion and deposition?" Using a plastic spoon, create a trench starting at the top of the mound and going all the way to the bottom to simulate a river bend. It can curve and branch. Hold a small funnel over the top of the river at the highest point and gently pour water so it flows into the river bed. See how the river flows to the bottom of the tray. Now pour the water a little faster/heavier to see how the water and soil is DEPOSITED at the bottom. Place some "houses", "rocks" and "trees" (using various items to simulate these) along the riverbed. ask: How do the trees help? (they help divert the water and prevent items from getting washed away ask: What happens to the houses if the river floods? (The houses can be washed away with the water). Part 4: Gravity Erosion Objective: to determine the effect of gravity on erosion and deposition. Gradually lift the back end of the blue tray (where the soil is mounded) and place it on the wooden supports - BE SURE THAT THE TRAY IS STILL DRAINING INTO THE BUCKET. ask: What does raising one side of the table model? (land/mudslide) Add more water and create a mudslide/landslide.

6 Part 5: Find evidence of erosion and deposition in the real world. Have the students look at the posters provided to find pictures that show where wind blowing sediment, water flowing, or gravity has caused erosion and have them record the picture number and the landform on the chart. Have the students look at the posters provided to find pictures that show where deposition has occured. Part 6: Extending your thinking ask: What would happen if large quantities of water were poured on the entire stream table, rather than just one area? What is this modeling? (floods, hurricanes, heavy downpours) Have the students record their thoughts. ask: What things do humans put in place to protect soil and structures from this types of water damage and erosion? ask: What are some other features of wind or water erosion that could be modeled in the stream table? Try to make a "flood" to test these ideas.

7

8

9