1. Forces That Shape the Earth

2. Earth’s Exterior-Spheres of the Earth

3. Earth’s Exterior & Interior-Layers of the Earth

4. Internal Forces That Shape the Earth-Plate Tectonics
Earth’s crust is made of plates that float on magma.
These plates were once together as the supercontinent “Pangaea”
They have since spread apart

5. Plate Boundaries Earth’s plates fit together like a puzzle
There are 3 types of plate boundaries
Oceanic-oceanic
Continental-continental
Oceanic-continental

6. Plate Movement
The plates that border each other move slightly as the float on the circulating magma
This circulation results from convection
Hot magma rises from the center of the earth towards the crust-as it moves away from the earth’s hot core, it cools down
When it cools it becomes heavier and denser and sinks back downward

8. Plate Movement

9. Plate Tectonics: Plate Movement
Four Types
Divergent
Convergent
Subduction
Collisional
Faulting/Transform

10. Plate Movement: Divergent Boundaries

11. Plate Movement: Convergent Subduction

12. Plate Movement: Convergent Collisional

13. Plate Movement: Faulting/Transform Boundary

14. Plate Tectonics in Action

15. The Exception- Hot Spots
plumes of stationary hot material
plate moves slowly above it.
spot melts through the plate like a blow torch creating a volcano above it.
As the plate moves, the spot melts through another spot producing a chain of volcanic islands
Hawaii is an example of a hot spot island chain.

16. External Forces That Shape the Earth-The Gradational Process
Gradational forces tear down and build up the earth’s surface. They include:
Weathering
Erosion
Deposition

17. Weathering is the process that changes the surface of exposed rocks
Breaks rocks up into smaller bits
2 primary types of weathering
Mechanical/Physical
Breaking things by force
Hitting, scratching, cracking (wedging)
Chemical
Chemical interactions

18. Mechanical Weathering
Something gets in & actually breaks it
wedging: something physically gets into the rock and expands breaking the rock
Roots/Plant wedging
Frost action
Exfoliation: rubbing from something strips layers off the rock

19. Mechanical Weathering: Plant/Root Wedging
Tiny root hairs seek out small cracks and pits in rock.
Once the root hairs find a place they grow and expand.
The expansion causes great pressure and cracks the rock.

20. Mechanical Weathering: Frost Action/Ice Wedging
Water seeps into small cracks in rocks.
When the water freezes it expands creating great pressure.
The crack widens and allows water to seep deeper into the rock.
The cycle continues over time

21. Mechanical Weathering: Exfoliation
This occurs with abrasion from sediment moved by:
Water
Wind
Rocks on rocks

22. Chemical Weathering
rock material is changed into another substance by chemical reaction.
Agents of chemical weathering
Oxidation
Hydration/Hydrolysis
Acid precipitation

23. Chemical Weathering: Oxidation
Chemical reaction between minerals and oxygen
Combination creates rust

24. Chemical Weathering: Hydration/Hydrolysis
Chemical reaction with water contact
Hydration
Water molecules are added to the composition of the material causing expansion and weakness that leads to breakage
Hydrolysis
Water dissolves and leaches out material that comes to the surface, turns to powder, and rubs off

25. Chemical Weathering: Dissolution
Minerals are dissolved usually by water with high acidity
CO2 emissions into the atmosphere create carbonic acid in precipitation and dew

26. What Factors Influence the Rate of Weathering?
Amount of surface area exposed
More surface= faster weathering
Mineral composition
Rock w/iron ore=oxidation
Shale is flaky so breaks up more easily
Climate
Cold and/or dry climates favor physical weathering.
Warm and wet climates favor chemical weathering.
Frost action works best in areas where the temperature fluctuates wildly.

27. Erosion The second part of the gradational process
Moves broken sediment through
Water
Wind
Glaciers
Gravity
This process works in conjunction with deposition, the final phase of the gradational process
In deposition eroded material is deposited creating new landforms

28. Erosion: Water

29. Erosion: Wind

30. Erosion: Glacial

31. Erosion: Gravity This is also known as mass movement or mass wasting
Results when angle can no longer sustain weight
a sudden release occurs
Ex: avalanche or mudslide

32. Mass Movement in Action

33. Deposition The “end” stage of the gradational process
It is where the weathered material is finally put down or deposited