Download Plate Boundaries

What Motions Occur at
Plate Boundaries?
WHAT ARE THE THREE MAJOR PLATE
BOUNDARIES?
DIVERGENT BOUNDARIES

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Plates move away from
each other as magma
rises in convection cells
Only occurs along midocean ridges
Seafloor spreading will
create new oceanic crust
Age of the rocks increase
as distance from the ridge
increases
Extreme Ecosystems –
Hydrothermal Vents
HYDROTHERMAL VENT COMMUNITIES
CONVERGENT BOUNDARIES
Two
plates Colliding where
convection cells are sinking.
What happens when the
plates collide is determined
by the types of crust that are
colliding
OCEANIC CRUST
CONTINENTAL CRUST
Density = 3.0 g/ml
 Basalt – mafic
/denser
 Thinner
 Younger


Density = 2.7 g/ml
 Granite – Felsic/less
dense
 Thicker – mountains
 Older
CONVERGENT: OCEANIC VS CONTINENTAL
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Oceanic Crust is Denser
(Basalt / Mafic) so it sinks
under the Less Dense
Continental Crust
(Granite/Felsic)
Subduction Zone with
deep focus earthquakes.
Trench forms –deepest
parts of the ocean
Mountains – form on the
surface as the continental
crust crumbles into the
oceanic crust
Yellowstone hotspot
X
X earthquake focus
X
X
X
Which one is Denser?
What do Denser Objects
Do?
EX: WEST COAST OF SOUTH AMERICA
Turn to pg 5 of the Handy
Dandy ESRT
 Feature
found
below the Surface
– Peru Chile
Trench
 Surface feature –
Andes Mountains
ANDES MOUNTAINS
CONVERGENT: CONTINENTAL VS CONTINENTAL
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Once all the oceanic crust has
been subducted the
continental crusts collide
Both crustal plates have the
same density and they
crumble into each other and
move up creating the tallest
mountains (neither is
subducted).
Earthquakes – due to friction
btn the continents ***Not as
deep as those on subduction
zones
Ex: Himalayans-Created by
India colliding into Asia
Himalayan formation 2
CONVERGENT: OCEANIC VS OCEANIC
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Deepest Trenches form
Ex: Mariana’s Trench –
Deepest section of the
ocean (Pacific Plate
Colliding into the
Phillippine Plate)
Tonga Trench Erupting
Video of Underwater
Eruption
TRANSFORM BOUNDARIES

Plates slide past each
other
small transform boundaries occur along
other types of boundaries.

San Andreas fault
(California) is the
longest transform
boundary
LET’S REVIEW
Lets review all the boundaries
Quiz challenge