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Plate Tectonics
What 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