Building Up Earth’s Surface

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# Building Up Earth’s Surface - PowerPoint PPT Presentation

Building Up Earth’s Surface. Unit C Chapter 6 Lesson 3 C24 – C29. Objectives. Recognize that constructive forces build up Earth’s surface features. Recognize deposition to be the dropping of sediments by water, wind, or ice.

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### Building Up Earth’s Surface

Unit C

Chapter 6 Lesson 3

C24 – C29

Objectives
• Recognize that constructive forces build up Earth’s surface features.
• Recognize deposition to be the dropping of sediments by water, wind, or ice.
• Understand that gravity is always the final process in sedimentation.
Main Idea
• Forces such as deposition and volcanic activity build up Earth’s surface features.
Review
• In the last lesson we discussed how the earth wears down.
• The process of weathering and erosion.
• Erosion carries away sediment, but what happens to it then?
• When it is dropped or released in a new area this is called deposition.
Deposition
• Deposition is a constructive force.
• This means it builds up the land.
• When the sediment is dropped in a new location, you are adding to the existing land there. You are building it up.
River Systems
• Recall that the source of a river is usually inland at some high elevation.
• The water picks up sediment as it flows downward.
• At the mouth of the river the water empties into a lake or ocean.
• The mouth is level, causing the water to lose energy and drop the sediment.
Alluvial Fans
• Is a fan-shaped land mass that forms after a river rushes down a steep slope, then slows over a flat plain.
Delta
• A low plain that forms where a river enters an ocean.
• If the river is large, so is the delta.
• The Mississippi River has a large delta that extends out into the Gulf of Mexico.
Meanders
• As a river flows across a flat plain, its course begins to wind in curves called meanders.
• They increase in size as water erodes the outside of each curve and deposits sediment on the inside.
Flooding
• Flooding of rivers on lowlands deposits sediment.
• This sediment builds up the flood plain.
• Because the sediment slows down and settles out.
How are Earth’s surface features built up?
• Through forces such as deposition and volcanic activity.
What is the difference between an alluvial fan and a delta?
• Both form when the flow of river water decreases quickly.
• An alluvial fan forms where a river flows down a steep slope onto a flat plain.
• A delta is a low plain, and forms where a river enters an ocean.
Pushing up Earth’s Surface
• Surface features can be pushed up from below.
• Below earth’s surface the temperature is so hot it melts rock.
• Melted rock below the Earth’s surface is called MAGMA
Magma
• Originates in a layer just below the crust.
• Pressure causes magma to push up Earth’s crust creating round, dome-shaped mountains.

Mount Olympus

Magma surfaces
• Magma can work its way through the crust.
• When it flows onto Earth’s surface it is called LAVA.
• As lava flows, it cools and hardens into rock.

Kilauea, Hawaii

Shield Cones
• Lava that has built up to form a huge deposit with gentle sloping sides.
• Often form on the ocean floor.
• The Hawaiian Islands are the tops of shield cones.
Hot Spots
• The Hawaiian Islands were formed due to a hot spot.
• As the Earth’s crust moves over the hot spot, new shield cones are formed.
Building Mountains
• The Himalaya Mountains in Central Asia were formed from a different constructive force than magma.
• As the Earth’s plates moved, they moved into each other.
• The pressure caused the crust to fold upward.
Remains
• The remains of living things can build up Earth’s surface.
• The chalk cliffs of Dover, England are made of shells of tiny sea animals.
• The shells eventually raise to the surface.
Coral Reefs
• Another type of formation produced from the remains of living things.
• In shallow tropical waters, tiny animals called corals gather in colonies.
• As they die, their skeletons build up into a bumpy ridge called a reef.
What process created the Himalayas?
• They formed when huge sections of Earth’s crust pushed into each other.
• Both are formed from remains of living things.
• Chalk cliffs are made of the shells of tiny sea animals that were deposited on the sea floor millions of years ago, then raised to the surface.
• Coral reefs are the skeletons of tiny animals called corals that build up in tropical waters
Glacial Deposits
• As we learned in Social Studies thousands of years ago there were large glaciers over Asia, Europe, and North America.
• The ice chunks were forces of erosion.
• Huge amounts of soil & rock were pushed ahead of the ice and carried along in the glacier’s bottom layers.
Glaciers
• The ice melts
• It had changed the landscape.
• Rock material deposited by a glacier is called till.
• Till is dragged along the icy base.
Glacier Moraines
• Moraines are deposits of till at the front or snout of a glacier.
• Long Island, NY is the terminal moraine left when the last ice sheet melted.

Exit Glacier in Kenai Fjords National Park near Seward, Alaska

Eskers
• Steams flowing through tunnels in melting glaciers deposit sand & gravel in ridges.
• These winding ridges are called eskers.
• deposition
• crust