Plate TectonicsWhat evidence do scientists have to support the fact that the Earth’s crust
is continuously moving?
Plate Tectonics
• The theory that describes how tectonic plates move and shape Earth’s surface
• Tectonic plates are huge pieces of crust that fit together at their edges to cover Earth’s surface.
About 12 plates exist on Earth
Earth’s Interior• Crust – Rigid outer shell
of Earth– Oceanic and Continental
Crust
• Mantle
– Upper mantle is partially molten
– Lower mantle is rigid (solid)
Earth’s Interior
• Core– Outer core is
molten iron, source of Earth’s magnetic field
– Inner core is solid, Iron and Nickel
Plate Boundaries
Divergent Boundary
Convergent Boundary
Transform Boundary
Divergent Boundary
• Two tectonic plates move apart from each other
• Rift valleys – long narrow depressions
• Rift valley in East Africa
Convergent Boundary
• Two tectonic plates move towards each other (come together)
• Oceanic Plates are more dense
• Continental Plates are less dense
Subduction• Process when one tectonic plate slips
beneath another plate
• Oceanic – Oceanic
– Subduction Occurs
– Deep Sea Trenches (Marianas Trench)
• Oceanic – Continental
– Subduction Occurs
– Trench and Volcanic Arch (Peru – Chile Trench)
• Continental – Continental
– Mountain Building
– Himalayas
– Aleutian Islands
Transform Boundary
• Region where two plates slide past each other
• Earthquakes occur at transform boundaries
• San Andreas Fault in San Francisco