Transcript Plate Tectonics - Mrs. DiLorenzo Earth Science

Plate Tectonics
The Plate Tectonic Theory
• Earth’s lithosphere is
broken into pieces called
plates, and their
movement creates major
changes in Earth’s
surface.
At least 3 times in
the past, most of
the large
landmasses have
come together,
forming
supercontinents.
Plate Boundaries
Plate
Boundaries
Movement
Divergent
AWAY from
each other
Convergent
TOWARDS
each other
Transform
SIDEWAYS
Arrows
on Map
Type: Divergent Plate Boundary
Key Characteristics: New crust is made
Example: Mid-Atlantic Ridge
Type: Oceanic-Continental Convergent
Key Characteristics: subduction, trenches,
volcanoes, deep earthquakes
Example: Peru-Chile Trench
Mariana’s Trench = deepest point on Earth (35,
feet deep)
Aleutian Trench
Type: Continental-Continental Convergent
Key Characteristics: Mountain Building
Example: Himalayas
Type: Transform Fault
Key Characteristics:
• Slide past one
another
• Shallow
Earthquakes
Example: San Andreas
Fault
What DRIVES Plate Tectonics?
• The current accepted theory
about what makes the
plates move:
– CONVECTION CURRENTS in
the mantle pushes plates
apart or towards each other.
Divergence
Convergence
Convergence
Subduction
Hot, ____________ dense material formed deep within
Earth’s mantle rises. When this material cools near the
surface, it becomes ______________dense and sinks. The
resulting convective flow of this material in the mantle
___________________ lithospheric plates across the surface
of the Earth.
Hot Spots
• Hot Spots: major regions of volcanic activity in the
interior parts of plates
• EX:
Animation
Kauai
4 my old
Molokai
Oahu
2.5 my old 1.5 my old
Hawaii
Maui
1.2 my old 0 my old
Effects of Plate Tectonics
1. Appearance of Continents: the outlines of
present-day continents appear to fit together like
puzzle pieces.
Effects of Plate Tectonics
2. Similar landmass features: minerals, rocks, fossils, age,
and mountain ranges are found at places where
continents have joined together in the past.
The reptile Mesosaurus swam in the freshwaters of
Pangaea 260 million years ago. Today, its fossils are
only found in Africa and South America.
Effects of Plate Tectonics
3. Age and Heat Patterns of Oceanic Rocks: as you move
further away from a mid-ocean ridge, the crust gets older
and cooler.
Effects of Plate Tectonics
4. Magnetic Stripes: the ocean floor shows a pattern of
magnetized “stripes”, recording reversals in Earth’s
magnetic field.
Video Clip
Animation
Paleomagnetism
The Earth's magnetic field
produces invisible lines of force
that extend from one pole to the
other.
A compass needle aligns itself
with these lines of force — points
toward the magnetic poles.
When igneous rocks containing
magnetic minerals crystallize, the
crystals align themselves with
the Earth's magnetic field.
The magnetic field of the rock
then points toward the magnetic
pole that existed when the rock
formed. If the rock is moved, its
magnetic field will act as a "fossil
compass."
demo