Geology Reference
In-Depth Information
◗
Figure 2.18
Three Types of Convergent Plate Boundaries
Oceanic-oceanic plate
boundary. An oceanic trench
forms where one oceanic plate
is subducted beneath another.
On the nonsubducted plate, a
volcanic island arc forms from
the rising magma generated
from the subducting plate. The
Japanese Islands are a volcanic
island arc resulting from the
subduction of one oceanic plate
beneath another oceanic plate.
M
ar
gin
a
l s
ea
(b
a
ck
a
rc
)
Volcanic
island arc
Central
ocean
a
Continent
Back arc spreading
U
p
p
e
r
m
a
n
t
l
e
l
A
s
t
h
e
n
o
s
p
h
e
r
e
Mantle upwelling
associated with
nearby subduction
c
Japan
Partial
melting
Subducting
oceanic crust
Panama
Amazon
River
Oceanic-continental plate
boundary. When an oceanic
plate is subducted beneath a
continental plate, an andesitic
volcanic mountain range is
formed on the continental plate
as a result of rising magma.
The Andes Mountains in Peru
are one of the best examples
of continuing mountain building
at an oceanic-continental plate
boundary.
b
N
Continental
interior
Pacific
Ocean
Vocanic arc
mountain range
C
o
nt
in
e
nt
a
l
cr
us
t
Subduction
complex
0
1000
Km
Partial
melting
Subducting
oceanic crust
Secondary rifting
caused by collision
India
N
Mountain range
Indian
Ocean
Rift
faulting,
Tibetan
plateau
Co
nt
ine
nt
al
c
rus
t
0
1000
Km
Co
nt
ine
nt
al
c
rus
t
Continental-continental plate boundary. When two
continental plates converge, neither is subducted because
of their great thickness and low and equal densities. As the
two continental plates collide, a mountain range is formed
in the interior of a new and larger continent. The Himalayas
in central Asia resulted from the collision between India and
Asia approximately 40 to 50 million years ago.
c
T
hru
st
zo
ne
Oceanic
crust
Little or no
partial melting
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