1. Weathering, Erosion and Natural Catastrophes

2. Weathering
Weathering is the process that breaks down rock and other substances at Earth’s surface.

3. Erosion
Erosion is the movement of rock particles by wind, water, ice, or gravity.

4. Working together
Weathering and erosion work together continuously to wear down and carry away the rocks at Earth’s surface. Weathering breaks rock down and erosion carries it away.

5. 2 Types of Weathering There are 2 types of weathering:
Mechanical and Chemical

6. Working together
As mechanical weathering breaks rock into pieces, more surface area becomes exposed to chemical weathering. So, they also work together.

7. Mechanical Weathering
The type of weathering in which rock is physically broken into smaller pieces is called mechanical weathering.

8. Agents of mechanical weathering
Freezing and thawing
Release of pressure
Action of animals
Growth of plants
Abrasion - rock particles carried by wind, water, ice and gravity.
Water expands when it freezes, and acts as a wedge.
This process is called ice wedging.

9. Mechanical weathering

10. Ice Wedging

11. Chemical Weathering
Chemical weathering is the process that breaks down rock through chemical changes.

12. Agents of chemical weathering
The agents of chemical weathering include:
water
Oxygen (oxidation is a reaction w/ O2)
carbon dioxide ( carbonic acid)
living organisms( plant roots produce weak acids)
acid rain

13. Weathering from acid rain

14. Rates of weathering
The most important factors that determine the rate at which weathering occurs are the type of rock and climate.
Ex: Some rock weathers easily because it is permeable, which means that it is full of air spaces that water gets through.

15. Chemical weathering
Water is the most important agent of chemical weathering.
Water weathers rock by dissolving it.
The oxygen in air is an important cause of chemical weathering.
Plant roots produce weak acids that slowly dissolve any rock around the roots.
Lichens also produce a weak acid that weathers rock.
Acid rain causes very rapid chemical weathering.

16. Erosion The material moved by erosion is sediment.
When the agents of erosion lay down sediment, deposition occurs.
Deposition changes the shape of the land.

17. Erosion

18. More erosion

19. Cycle of erosion
Weathering, erosion, and deposition act together in a cycle that wears down and builds up Earth’s surface.
Erosion and deposition are at work everywhere on Earth. Sometimes, they work slowly. At other times, they work more quickly.

20. Agents of Erosion

21. Water
The major agent of erosion
Shapes Earth’s land surface

22. Runoff Erosion
Gully
Rill

23. Wave Erosion

24. River and Stream Erosion

25. Glacial Erosion
Caused by gravity pulling glacier down

26. Wind Erosion Wind itself is the weakest cause of erosion.
Greatest impact is on an area that has few plants to hold dry soil in place

27. Gravity is the force that moves rock and other materials downhill.
Gravity causes mass movement, any one of several processes that move sediment downhill.
Mass movement can be rapid or slow.

28. Mass Movements The different types of mass movement include:
Landslides – rock and soil slide quickly down a steep slope.
Mudslides -the rapid movement of a mixture of water, rock, and soil.
Slump – a mass of rock and soil suddenly slips down a slope in one large mass.
Creep – very slow downhill movement of rock and soil.

29. Landslides

30. Mudslide

31. Slump

32. Creep

33. Natural catastrophes
A natural catastrophe/hazard is an event that results from Earth processes and that can cause damage and endanger human life.

34. And the natural catastrophes are…
droughts
wildfires
floods
the different types of mass movement
tsunamis
hurricanes
tornadoes
earthquakes
volcanoes
other storms

35. Volcano

36. Earthquake

37. Tornado

38. Hurricane

39. Catastrophic events can affect Earth in several ways.
Catastrophic events that result from surface processes may speed up erosion and deposition.
Catastrophic events resulting from processes inside Earth change the crust itself (volcanoes).

40. People, People, People
Where people locate their activities can increase the damaging effects of natural hazards.
How people use land also alters Earth systems in ways that may cause catastrophic events.