Transcript Internal Forces that Shape the Earth (Plate Actions)

Internal Forces that Shape the
Earth (Plate Actions)
Plate Tectonics
• Continental Drift – plates move slowly
across upper mantle
• “Pangaea” – supercontinent existed 250
million years ago
Divergent Boundary
• Plates separate / spread apart
A. Mid ocean ridge
• Two ocean plates separate
B. Rift Valley
• Two land plates separate
Convergent Boundaries
• Plates collide
A. Mountains
• Two land plates collide
B. Island Chains
• Two ocean plates collide
C. Ocean Trench and Mountains
• Land and ocean plates collide
Transform Boundary
• Two plates slide against each other
A. Fault
V. Earthquakes and volcanoes
form along plate boundaries
External Forces that Shape the Earth
Weathering
• The breaking down of rock into sediment
Physical Weathering
Chemical Weathering
Erosion
• The carrying away
of sediment
A. Water is the greatest agent of erosion
B. Wind
C. Glaciers / Ice
Landforms
1. Created by tectonic processes
1. Mountains, valleys
2. Created by erosion
1. Plateau, plains
3. Created by sediment deposition
1. Sand dune, floodplain
Most regions have a
combination of all three types
Example:
Mountain range formed by tectonic activity.
Erosion forms deep valleys between the
mountains.
Sediment eroded from the mountains is
deposited at the mountains’ bases.
Creates an alluvial fan.
Alluvial fan: fan-shaped deposit of mud and
gravel often found at the base of mountains.
Stream erodes the sediment in the alluvial
fan and carries them to a river mouth.
Sediment moves into the ocean and sinks,
or it may accumulate and build a delta.