1. Chapter 4, Section 1 Landforms (part 2)
Focus Questions… (continued from part 1)
2. What physical processes on Earth’s surface wear down the land?
3. How do these physical processes interact to create landforms?

2. Weathering breaks rocks into smaller particles of gravel, sand, and mud
The first step in the formation of soil; it happens very slowly

3. Two kinds of weathering
Chemical weathering – water slowly dissolves certain rocks

4. Physical weathering – some forces cause rocks to crack, other forces pry rocks apart; also called mechanical weathering

5. Erosion wears away the rocks and transports them downhill
Water -
is the most
powerful
force of
erosion

6. Wind
Has its greatest effect where there are few plants, usually due to a dry climate
Why?
Wears down hard rocks by blowing particles of sand against them (like sandblasting)

7. Ice Glaciers Gravity pulls them downhill
Are large accumulations of snow and ice that move slowly over the land
Gravity pulls them downhill
Have the power to remove anything in their path

8. Glaciers around the world are melting – why is this happening?

9. Once the rocks are broken down and carried away, it’s time for the third step in the process: Deposition
These particles of sand, mud, and silt eventually find their way to the bottom of the ocean and become sedimentary rocks.

10. Landforms
We can classify landforms based on how they were formed.

11. 1. Landforms made by tectonic processes
Created by volcanoes, folding and faulting
Himalayas – highest mountains on earth
Death Valley – deep basin, below sea level
Mariana Trench – deepest part of the ocean

12. More Tectonic Landforms

13. 2. Landforms made by erosion
These are made of rock, with a thin layer of weathered sediments and soil at the surface
Surface is being slowly worn down by erosion
Harder rocks wear away more slowly
Examples - valleys, plains, plateaus

15. 3. Landforms made of sediments deposited by wind, water, or ice
Deposited by wind – sand dunes
Deposited by water – flood plain
Deposited by ice – glacial moraine

17. Weathering and Erosion
Weathering Erosion
Physical Processes
• Heating and cooling
• Freezing and thawing
• Tree roots
Chemical Processes
• Substances in air and water
Water
• Rainfall
• Rivers
• Waves
Wind
• Abrasion
• Move from one place to another
Ice
• Glaciers