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. 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 What Are Surface Features?

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

17. What Do You Think?

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