1. Forces of Change
Day 3

2. Earth’s Structure Think of the Earth as a hardboiled egg
Core—center of earth, very hot and solid; inner core made of iron and nickel under extreme pressure
Mantle—located next to the outer core, thick layer of hot, dense rock
Crust—outer layer; rocky shell forming the earth’s surface
Underneath the continents and oceans is a CRUST, underneath the whole crust is a warmer layer called the mantle, underneath that is the hot inner core in the center
Think of the Earth as a hardboiled egg
Thin brittle shell  Crust that humans live on
White, soft inside  Deep hot magma beneath the surface
Yellow, yolk beneath  Core of the earth

3. Plate Movement 500 million years ago—Supercontinent Pangaea
Continental Drift—Continents have slowly drifted apart
Plate Tectonics
Plates moving have produced Earth’s largest features
Continents, mountains, and oceans
Plates are crashing and spreading (but veryyy slowly)
Crust is actually broken into pieces or PLATES, it’s not just one, there’s many pieces
Pieces and plates actually move

5. Remember: Think about the plates as a hard boiled egg shell
Notice anything similar about the arrows? What are different
Have them notice that some are pointing toward and some are pointing away
Remember: Think about the plates as a hard boiled egg shell

6. What happens when plates meet?
Two important types of plate movements
Divergent
Convergent
Which one do you think matches the images below?
Convergent
Divergent

7. Divergent Plate Movement
Movement of plates in opposite direction
Spreading Process (step by step)
Sea plates pull apart—most happen in the ocean
Results in a rift (deep crack)
Magma from within the earth comes up between the plates
Magma hardens and builds new oceanic crust

8. Examples: Mid Atlantic Ridge and East African Rift Valley (Divergent Plates)
Snorkling at Mid Atlantic Ridge--
Underwater gorges (valley between mountains) caused by the spreading process

9. Convergent Plate Movement
Two plates coming together
Subduction
Heavier sea plate dives under the lighter continental plate
Crust starts to melt, returns to surface as volcanoes
Example: Andes Mountain range in South America
******If new crust is created (through spreading), then it must be destroyed some where, otherwise the Earth would grow, which it cannot. Crust is consumed in subduction zones.
Two plates can be two oceanic plates coming together, two continental, or combination of both
Lithosphere—rigid outer part of the earth, consisting of the crust and upper mantel (it is two different plates)
Asthenosphere—upper mantle of the earth, layer of solid rock that has so much pressure and heat the rocks so they can flow like a liquid. This allows the tectonic plates in the lithosphere to move around on the earth’s surface by floating on the rocks that are slowing flowing like a liquid

10. How are volcanoes formed?
Subduction causes volcanoes
How a Volcano is formed: (step by step)
Two plates meet (convergent plate movement)
One plate dives underneath
Plate partially melts (in the upper mantle it is very hot)
Makes magma that drills up to the top

11. How are Earthquakes formed?
Violent movements of tectonic plates—pull, push, or slide
How Earthquake is formed: (step by step)
Two plates meet and create a fault line
Massive pressure here
Intense pressure causes the fault lines to give way
Plates move over, against, or apart from each other
Earthquake happens
Waves of escaping energy radiate outward from the fault line
Waves reach earth’s surface and shake the ground
Making science fun with crackers and cheese

12. Earthquake Diagrams

13. External Forces of Change
How the Earth’s surface changes—Weathering and Erosion
Step one: breaking down of rocks (weathering)
Step two: rocks are carried away (erosion)
Wind erosion—movement of dust, sand and soil from one place to another
Glacial—as they move, they pick up rocks and soil in their paths; change landscapes, destroy forests, carve out valleys, alter course of rivers, and wear down mountains
Glaciers, when they melt, leave behind large piles of rocks and debris that may sometimes form dams
Water Erosion--Leftover sediment acts as sandpaper and grinds the surface of the rock

14. Water Erosion—Case study
Grand Canyon
Shaped by the Colorado River and widened by side streams
For the past millions and millions of years!
Weathering—wears away exposed surfaces over time
Rocks will crumble if water seeps into cracks
Erosion
Water carries away the rocks fragments and shapes the canyon

15. Knowledge Check
Weathering: the _____________________ _______________ of rock on the Earth’s surface
Erosion: The ___________________ _________ of particles of sediment
Answers:
Weathering—breaking down
Erosion: carrying away