Constructive and Destructive Forces Processes That Act Upon

Constructive and Destructive Forces Processes That Act Upon Earth’s Surface Features

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.

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

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

Constructive Force Examples of Deposition Constructive Process Deposition Surface Feature Deltas Floodplains Beaches and Barrier Islands Sand dunes Moraines and drumlins Force/Agent water / river water / ocean long-shore current wind Ice / glacier

Other Constructive Forces Constructive Surface Process Feature Folding Mountains Faulting Mountains Earthquake Trench Fault Mountains Islands Volcanic Activity Force Plate tectonics

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.

Changing the Earth’s Surface by a Destructive Force Examples 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

Destructive Force Examples of Erosion Destructive Process Erosion Surface Feature Force/Agent Canyons, Gorges, VShaped Valleys Water Sea Arches, Sea Stacks Buttes, Desert U-Shaped Valleys Mudslide, Sinkholes Water Wind Ice Gravity

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

Visit these sites • Land Formation

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?

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

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

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

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

What Do You Think?

Deposition is a process that… A. B. C. D. Dissolves sediment Breaks down rock to form sediment Removes sediment from landforms Drops sediment to form landforms

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

Long shore currents help create… A. B. C. D. Beaches Dunes Rivers Drumlins

Volcanoes can create new land when they release… A. B. C. D. Lava Water Faults Mud

What forms moraines and drumlins? A. B. C. D. Wind Rivers Glaciers Volcanoes

What landforms from deposition at the mouths of rivers? A. a delta B. a floodplain C. a sand dune D. a moraine

What is weathering? A. A type of climate B. The transport of sediment C. The breakdown of rock D. The aging of rock

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

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

A river can form … A. Sea arches. B. U-shaped valleys. C. V-shaped valleys. D. Desert pavement.

Deposition forms these features on coasts. A. drumlins B. floodplains C. barrier islands D. U-shaped valleys

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

A dam across a river can cause… A. the formation of a delta. B. the carving of a valley. C. the erosion of a beach. D. the formation of a sea stack.

Which of these helps prevent the harmful effects of erosion? A. dams B. volcanoes C. Long-shore currents D. contour plowing

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

What does erosion do? A. breaks down rock physically B. moves broken pieces of rock C. changes rock chemically D. change sediment into rock

Beaches that have eroded are reclaimed through… A. weathering. B. building of seawalls. C. beach nourishment. D. building of terraces.

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

Scientists know where earthquakes will occur because they know the locations of … A. faults B. volcanoes C. mountains D. long-shore currents.

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