Download Theory of plate tect

The Theory of
Plate Tectonics
Canadian scientist, J. Tuzo Wilson noticed
the continental crusts had cracks similar to
oceanic crust
Lithosphere is broken into sections
called plates
• Plate tectonicsgeologic theory
stating that pieces
of Earth’s
lithosphere are in
constant, slow
motion, driven by
convection
currents in the
mantle
The theory of plate tectonics explains
the formation, movement, & subduction
of Earth’s plates
• Plates meet at plate boundaries extending deep
in the lithosphere
• Faults- breaks in Earth’s crust where rocks slip
past each other form along boundaries
3 Types of Plate Boundaries
• Divergent
• Convergent
• Transform
Transform Boundary
• Crust is neither
created nor destroyed
• 2 plates slip past
each other moving in
opposite directions
• Earthquakes occur
frequently here
Divergent Boundary
• Place where 2 plates move apart
• Most found along mid-ocean ridge where
oceanic crust diverges
Divergent boundaries also occur
on land
• Rift valleys form when continental crust
diverges
• Rift may eventually split a continent
Convergent Boundary
• Place where 2 plates come together,
converge
• Collisions may occur between 2 oceanic
plates, 2 continental plates, or an oceanic
& continental plate
Oceanic-Oceanic Convergence
• Oceanic crust becomes cooler & denser
as it spreads away from the mid-ocean
ridge
• 2 oceanic crusts meet at a trench & the
more dense plate subducts under the
other plate & returns to the mantle
• Oceanic convergence creates island arcs
Oceanic-Continental Convergence
• Oceanic crust, made
of basalt, is denser
than continental crust,
made mostly of
granite
• Oceanic plate sinks
beneath the
continental crust
Continental-Continental
Convergence
• Subudction does NOT
occur when 2 pieces
of continental crust
collide
• Neither plate is dense
enough to sink
• Crust is squeezed
into mountain ranges
Continent’s Slow Dance
• Plates move at an extremely slow rate, 110 cm/year
• North American & European plate are
moving apart at about the same rate as
your finger nails grow
Tracking Tectonic Plate Motion
• Scientists use data
from a system of
satellites called
Global Positioning
System (GPS) to
measure the rate of
motion of tectonic
plates.
Review what you know…
• 1. Define plate tectonics.
• 2. Describe the three boundaries of plate
movement.
• 3. How do scientists measure the rate of
tectonic plate movement?