Transcript Tectonic Plate Boundaries and Their Effects Divergent Boundaries: Examples are East African Rift and Mid-Atlantic Ridge.

Tectonic Plate Boundaries and
Their Effects
Divergent Boundaries: Examples are East African
Rift and Mid-Atlantic Ridge
Divergent Boundaries
• Due to convection cells in
Mantle.
• Two plates move away
from each other.
• Results in volcanoes, rift
valleys, mid-ocean ridges.
• Youngest rock at
spreading ridge.
• Normally Basalt is
erupted to make new
oceanic crust.
Convergent Boundaries: Example:
Japan
Oceanic-Continental Convergent
• More dense oceanic crust
SUBDUCTS under less
dense continental crust.
• Called Subduction Zones.
• Forms volcanoes and
mountains from melting
of overlying continental
crust. Also earthquakes.
• Examples: Cascade
Mountains in Washington
and Andes Mountains in
South America.
Oceanic-Oceanic Convergent
• When older, more
dense oceanic crust
subducts under younger
oceanic crust.
• Results in deep
trenches (Marianas
Trench) and Island Arcs
of Volcanoes (Ex.
Japan). Also
earthquakes.
Continent-Continent Convergence
• When two continents
collide.
• Forms mountains and
deforms crust (folding
and faulting).
• Metamorphism also a
result
• Example: Himalayas and
ancient Appalachians.
Transform Boundaries
Transform Boundaries
• Plates slide past each
other.
• Results in shear,
bending, breaking, and
earthquakes.
• Offset: How much a
plate has moved over
time.
• Example: San Andreas
Fault in Calfornia.
Causes of Plate Movement
• Convection Cells
• Ridge Push
• Slab Pull
Convection Cells
• Hot magma rises in the mantle, heated by
earth’s core.
• The magma cools at it moves toward the the
crust and sinks.
• Opposing convection cells create friction on
the lithosphere that breaks it apart.
Ridge Push
• As the newer, warmer
rock cools and becomes
denser, it begins to slide
down the slope
between the
lithosphere and the
asthenosphere.