1. Forces that Change the Earth’s Surface

2. Earth’s Systems Lithosphere(troposphere) – rocks and land
Atmosphere - gases
Hydrosphere – water on the ground and in the atmosphere

3. External Forces
Weathering – The breakdown of rocks into smaller pieces.
Physical Weathering – changes size and shape
Ex. Frost Action
Chemical Weathering – changes chemical composition
Ex.Acid Rain and rusting
Erosion – Transporting material from its original location
Ex. Water, Wind, Gravity, Glaciers

4. Landforms Mountains – Formed by folding and faulting.
Also by volcanic lava cooling.
Plains – broad flat regions at low elevations
Plateaus – layers of rock at higher elevations
Built similar to mountains.

5. Earthquakes Earthquakes are the sudden sliding movement along a fault.
The vibrations travel in waves
Primary (p-waves), secondary (s-waves), and longitudinal (l-waves)
P – waves travel all through the earth
S – waves cannot travel through liquids like the outer core.
L –waves travel on the surface

7. Structure of the Earth Crust – outer layer made of rock, 5-50km thick.
Mantle – 2900 km thick, dense iron and magnesium rock
Outer Core – 2300 km thick made of liquid iron and nickel
Inner Core – 1200 km thick, made of solid iron and nickel

8. Plate Tectonics and Continental Drift
The Earth’s crust is broken up into 12 large plates and many smaller ones.
These plates slowly move and interact……mountains, earthquakes etc.
A theory was proposed that they are separating. At one time they were all together as one big continent called Pangea.
Evidence – ancient mountain ranges line up
Continents fit like puzzles.
Fossils

9. Pangea
Plates

10. Sea Floor Spreading New rock is made at the center of the ocean
Old rock is destroyed near the continents
Ex. Mid Atlantic Ridge