Building Up Earth’s Surface

1. Building Up Earth’s Surface Unit C Chapter 6 Lesson 3 C24 – C29

2. 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.

3. Main Idea • Forces such as deposition and volcanic activity build up Earth’s surface features.

4. 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.

5. 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.

6. 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.

7. Alluvial Fans • Is a fan-shaped land mass that forms after a river rushes down a steep slope, then slows over a flat plain.

8. 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.

9. 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.

10. Flooding • Flooding of rivers on lowlands deposits sediment. • This sediment builds up the flood plain.

11. Why is sediment deposited as the slope of a river bed levels out? • Because the sediment slows down and settles out.

12. How are Earth’s surface features built up? • Through forces such as deposition and volcanic activity.

13. 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.

14. 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

15. 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

16. 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

17. 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.

18. 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.

19. 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.

20. Himalaya Mountains

21. 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.

22. 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.

23. What process created the Himalayas? • They formed when huge sections of Earth’s crust pushed into each other.

24. 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

25. 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.

26. 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.

27. 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 

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

29. REVIEW

30. Small islands can form during the constructive process called? • deposition

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

32. The End