Building up earth s surface
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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.

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Building Up Earth’s Surface

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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.


Why is sediment deposited as the slope of a river bed levels out?

  • 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.


Himalaya Mountains


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.


How are chalk cliffs and coral reefs alike? How are they different?

  • 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.


REVIEW


Small islands can form during the constructive process called?

  • deposition


Landforms are found on the ______, which is Earth’s outer rocky layer.

  • crust


The End


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