Constructive and Destructive Forces

1. Constructive and Destructive Forces Processes That Act Upon Earth�s Surface Features

2. What are Constructive and Destructive Forces? Constructive Force A constructive force is a process that raises or builds up the surface features of the Earth. Destructive Force A destructive force is a process that lowers or tears down the surface features of the Earth.

3. What Are Surface Features? Surface features are landforms and bodies of water that cover the Earth�s surface such as: mountains valleys canyons gorges beaches sand dunes barrier Islands flood-plains moraines and drumlins volcanoes oceans lakes rivers

4. How Can a Surface Feature be Changed by a Constructive Force? Natural forces such as wind, water, ice, through the process of deposition. Deposition is the process of dumping sediment, dirt, rocks, or particles in one place. The movement of the Earth�s crust through Plate Tectonics

5. Constructive ForceExamples of Deposition

6. Other Constructive Forces

7. How Can a Surface Feature be Changed by a Destructive Force? Physical or Chemical Weathering Weathering is the breaking down of rock into sediment. Natural forces such as wind, water, ice, through the process of erosion. Erosion is the movement of sediment from one place to another.

8. Changing the Earth�s Surface by a Destructive ForceExamples of Weathering Mechanical / Physical Weathering Temperature Change-Freezing and thawing of Rock Ice Wedging-Water freezing and expanding in cracks of rock Impact of organisms Root Pry Animals burrowing Chemical Weathering Oxidation / rusting Carbonic Acid / acid rain Caverns Impact of organisms Secretion of acid from Lichen

9. Destructive ForceExamples of Erosion

10. Other Destructive Forces Volcanic Activity Movement of Earths Crust (Plate tectonics) Reshaping of Mountains Earthquakes Movement of Earths Crust (Plate tectonics) Trenches cracks in the Earth Curst

11. Visit these sites Land Formation

12. Controlling Constructive and Destructive Forces How can constructive and destructive forces be controlled through the use of technology? How does technology affect constructive and destructive forces? What are examples of technology used to control constructive and destructive forces?

13. Effects on the Control of Constructive Forces Dam � a structure built across a river to control its flow Positive Effect Flood Control Hydroelectric Power Negative Effect Holds back sediment Prevents deposition of flood plains, deltas, and beaches

14. Effects on the Control of Destructive Forces Prevention of beach erosion Groin � a structure built perpendicular to the beach. Positive Effect Traps sand that moves along the shore and causing the beach to build up. Negative Effect Beach Erosion down stream is worse. Seawall � a structure built parallel to the shore Positive Effect Protects land behind if from ocean the ocean waves Negative Effect Ocean side beach will erode Beach Nourishment � sand from ocean or nearby rivers are pumped onto the beach

15. Effects on the Control of Destructive Forces Prevention of soil erosion Contour Plowing � method in which farmers plow across the sided of hill instead of down Terracing � the planting of corps on terraces (steps) built into steep hillsides. Windbreaks � rows of plants or fences. Slow down wind and limit the distance it can carry soil. Vegetation � used to hold soil in place Storm drain management � a system of drains Prevents flooding and soil erosion

16. Can Volcanoes and Earthquakes be Controlled? Volcanoes and Earthquakes can not be controlled; However scientist have ways to determine when and where these they might occur. Volcanoes � instruments are used to detect changes in volcanoes Earthquakes � Detailed maps show major faults Safety Education No new buildings on or near faults Building codes to resists earthquakes Seismographs � measures earthquakes on a rector scale

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18. Deposition is a process that� Dissolves sediment Breaks down rock to form sediment Removes sediment from landforms Drops sediment to form landforms

19. Where do deltas form? In desert areas At river mouths On the banks of rivers In valleys formed by glaciers

20. Long shore currents help create� Beaches Dunes Rivers Drumlins

21. Volcanoes can create new land when they release� Lava Water Faults Mud

22. What forms moraines and drumlins? Wind Rivers Glaciers Volcanoes

23. What landform forms from deposition at the mouths of rivers? a delta a floodplain a sand dune a moraine

24. What is weathering? A type of climate The transport of sediment The breakdown of rock The aging of rock

25. Which of these is caused by chemical weathering? desert pavement formation of U-shaped valleys formation of rust ice expanding in cracks in rock at is weathering?

26. How do earthquakes change the land? They transport sediment. They form cracks in the surface. They release ash and lava. They cause chemical weathering.

27. A river can form � Sea arches. U-shaped valleys. V-shaped valleys. Desert pavement.

28. Deposition forms these features on coasts. drumlins floodplains barrier islands U-shaped valleys

29. What causes V-shaped valleys to form? deposition at river mouths erosion by rivers weathering by wind erosion by glaciers

30. A dam across a river can cause� the formation of a delta. the carving of a valley. the erosion of a beach. the formation of a sea stack.

31. Which of these helps prevent the harmful effects of erosion? dams volcanoes Long-shore currents contour plowing

32. In which type of climate are you most likely to find a sand dune that is not on the coast? dry humid icy hot

33. What does erosion do? breaks down rock physically moves broken pieces of rock changes rock chemically change sediment into rock

34. Beaches that have eroded are reclaimed through� weathering. building of seawalls. beach nourishment. building of terraces.

35. Which of these is not a way to prevent soil erosion? planting vegetation contour plowing building windbreaks building dams

36. Scientists know where earthquakes will occur because they know the locations of � faults volcanoes mountains long-shore currents.

37. Which of these do scientists use to predict when a volcano is likely to erupt? the age of the volcano earthquakes beneath the volcano temperature of nearby rivers the hardness of rock near the volcano