Water Cycle and Erosion

Transcription

1 Water Cycle and Erosion Objectives: Define evaporation, transpiration, condensation, percolation, and precipitation Explain the water cycle Define the term erosion Demonstrate sand erosion and discuss its effects on the earth Missouri Curriculum Frameworks: 3-4: Strand I Scientific Inquiry (A. Processes of Scientific Inquiry) 7a. use simple equipment to observe more detail, measure more accurately, and obtain more information about the environment in order to develop more accurate explanations (1.4, 1.6) Strand VI. Earth Science (B. Processes of Systems) 7a. select and apply problem-solving strategies using prior knowledge and experiences to show how and where Earth s surface is continually changing (1.10, 3.2, 3.3) 5-8: Strand VI. Earth Systems (B. Processes of Systems) 1a. exchange information, questions, and ideas with others to discuss the effects of energy transfer on the water cycle (2.3) Materials: Large plastic cups labeled Ocean Medium plastic cups labeled Cloud Medium plastic cups labeled River or Lake Small plastic cups labeled Plant Small plastic cups labeled Land Water Observing Water Erosion Activity For every 1-4 students: Wax paper Eye dropper Sand *This activity can be done using a stream table Discussion: Tell the students that the two major components of the Earth are matter and energy. The energy that we use ultimately comes from the sun. Energy is used to provide food for plants, heat our homes, power the wind, and ultimately, create fossil fuels. Once energy is used, it must be replaced. All matter that is on or in the earth already exists here. That means that there is a certain amount of air, water, minerals, and rocks on this planet. In order for all the matter to keep being used, it must be recycled in nature. For example, the water cycle is a cycle in nature.

2 Explain to students that approximately ¾ or the Earth is covered with water. Of this water, approximately one percent is the fresh water on which we depend. The fresh water that we use and its continuous replacement is the result of the water cycle. Point out that water is unique because it is one of the few materials on the Earth that exists naturally as a solid, liquid, or gas. Changes in state are caused by changes in energy. Changes in this energy, which ultimately comes from the sun, are measured by changes in temperature. 1. Pass out cups half full with water to the students. 2. Tell the students that when we think of the water cycle, we often think of bodies of water on the surface of the Earth, such as lakes, oceans, rivers, and streams. Water from these surfaces enters the water cycle upon evaporation. Evaporation occurs when the water is changed into a gas called water vapor. When the water vapor cools, it condenses to form clouds. 3. Have the Oceans and Rivers pour their water into the Cloud cups. 4. Tell students that plants also release water into the air in the form of water vapor by transpiration. Explain that plants collect water through their roots and lose it as it evaporates into the atmosphere through small openings on the undersides of their leaves. 5. Have the Plants pour their water into the Cloud cups. 6. Explain to the students that as water vapor cools into clouds, many things can happen, depending on the temperature. If the clouds stay relatively warm, the water vapor will collect into large drops until it is too heavy to stay up, creating rain. This is called precipitation. Precipitation returns water from the atmosphere back to the surface of the Earth. If the clouds are cold enough, precipitation could be in the form of snow or hail. 7. Instruct the Clouds to pour their water into the River, Land, and Ocean cups. 8. Inform the students that when water returns to the Earth, it can be absorbed into the soil. This process is called percolation. This is how the plants get their water supply. 9. Instruct those with Land cups to pour some of their water into the Plant cups. 10. Inform the students that the water that stays above the rock level and saturates the soil is called ground water. Some of this water can run off into rivers and some of the ground water is absorbed into lower levels of the Earth, which travels into lakes and ponds. 11. Have the students with Land cups pour some of their water into the Lake and River cups. 12. Tell the students that some of the water from rivers runs off into the ocean. 13. Let the students with River cups pour a little of their water into the ocean. 14. Explain to the students that precipitation that falls to the ground or the surface of bodies of water can once again evaporate, starting the water cycle over again. Discussion: Tell the students that when water is not absorbed into the ground, it can create surface runoff. Runoff water travels over the surface of the ground and causes erosion. Every year, water moves tons of soil, sand, and rocks. Erosion changes the Earth s crust. Tell the students that they are going to do an experiment that demonstrates sand erosion.

3 Sand Erosion Activity 1. Give each student or group of students a small amount of sand on a piece of wax paper, a small cup of water, and an eyedropper. 2. Instruct the students to fill their dropper with water and let one drop of water fall on the sand. Ask the students to explain what happened. (The mound did not change much.) 3. Have students squirt all the water from their droppers into one place on the sand. Have them refill the dropper several times. Squirt all the water in the same place. Ask, What happened when you let the water fall quickly on the sand in the same place? (Water quickly flowed down the mound and left a dug-out path.) 4. Ask students to apply what they just learned by asking how a heavy rainfall or flood might change the Earth s surface. (For example, the rain could wear down the soil on hillsides.) Ask, What are some things that can be done to prevent erosion?

4 Water Cycle and Erosion Lab Write Up Name Date Please answer the following questions in complete sentences. 1. What is evaporation? 2. What is transpiration? 3. What is condensation? 4. What is percolation? 5. What is precipitation? Sand Erosion Activity 6. What happened when you let one drop of water fall on the sand? 7. What happened when you let the water fall quickly on the sand in the same place?

5 8. How might a heavy rainfall or flood change the Earth s surface? 9. What are some things that can be done to prevent erosion? 438 St. Louis Street * Springfield, MO * Phone: * Fax: