Download Plate Boundaries and Interactions

Plate Boundaries and
Interactions
(ICS Pages 80-85)
• As you know, extremely hot magma near
the Earth’s center becomes less dense
and rises towards the surface where it
pushes upon the lithospheric plates.
• Today we will discuss the effects this has
upon the lithospheric plates, and how
lithospheric plates can affect each other.
• There are 3 main types of interactions
plates can have at their boundaries.
1) Divergent Plate Boundaries
= 2 tectonic plates are pushed apart
I I
– Also called a “spreading ridge”
– Can happen between 2 oceanic plates or
between 2 continental plates
A) Oceanic-Oceanic Divergence
– Less dense magma rises, creating undersea
volcanoes and creates new oceanic crust.
– Also called the “mid-ocean ridge” or “sea-floor
spreading”.
B) Continental-Continental Divergence
• 2 Continental plates push
apart.
– Magma pushes the crust
up. As it bulges and
cracks, it can collapse to
create a rift valley.
Continental-Continental Divergence
Continued
• If the land falls below
sea level the ocean
may invade the rift as
it widens, splitting the
land and creating a
new sea.
2) Convergent Plate Boundaries
• Two plates move
toward each
other.
I I
A) Oceanic – Continent Convergence
• The more dense oceanic plate subducts (is
pushed underneath) towards the mantle. A
volcanic arc is created on the continental crust as
the subducting oceanic plate melts.
B) 2 oceanic plates
• The more dense oceanic plate subducts. As
magma rises, a volcanic island chain is formed.
C) 2 continental plates
• Continental crust isn’t dense enough to subduct,
so mountains are created.
• 1 moves under the other, pushing the land up into
mountains, and locking it together at the “suture
zone” into a single continent.
3) Transform Plate Boundaries
• Plates slide past each other. The surface
of the plates that rubs together = a
transform fault.
I I
• Ex. San Andreas Fault