convergent boundaries - mr. schermer, crescent middle school · 2018-09-07 · symbols white arrows...
TRANSCRIPT
Mountains & valleys
Spreading center—Fast Spreading center—SlowDivergent boundaries occur mostly along spreading centers where the magma rises forming new crust. (Ex. East Pacific Rise, Mid Atlantic Ridge.)
Spreading zones (no graphic) on continents create parallel mountains and valleys as the crust pulls apart (ex: Basin & Range, U.S. and the Great Rift Valley, Africa. )
Divergent Boundaries & Spreading Zones
Lithosphere
Asthenosphere
Oceanic crust
Mantle
Partial meltAsthenosphere
Crust
MantleL ithosphere
Partial melt
Convergent Boundaries
Mo
un
tain
Ran
ge
Old oceanic crust
Cont inental crust
HighPlateau
Continental crust
L i thosphere Lithosphere
Asthenosphere
Trench
Oceanic crust
Cont inental c rust
L i thosphere Lithosphere
Asthenosphere
Asthenosphere
Isla
nd
arc
Oceanic crust
When two plates move toward each other, crust is destroyed as one plate dives (is subducted) beneath the other. The location where sinking of a plate occurs is called a subduction zone.
Ocean-Ocean—Ocean plate dives beneath another ocean plate; volcanic island chain forms above the zone (ex:. The Marianas)
Ocean-Continent: Ocean plate dives beneath a continental plate. Volcanic mountain chain forms inland. (ex:. Cascade Range, Sumatra, Japan)
Continent-Continent: Two thick continental plates collide and buckle into high mountains. (ex: Himalaya Mountain Range.)
Trench
Cont inental c rust
L i thosphere Lithosphere
Asthenosphere
Vo
lca
nic
a
rc
..
..
..
........
..
.. . .
Oceanic crust
Transform Boundaries
As surrounding plates are driven by deep forces to move apart or crunch together, the in-between areas are pushed around on the surface. This forces them to slide past each other horizontally.
Transform faults are where two plates are moving away from a spreading ridge and fracture zones develop (ex: ocean floor)
Asthenosphere
Crust
L i thosphere
Asthenosphere
Crust
Transform fault
L i thosphere
Spreading ridge
Partial melt
Spreading ridge
Strike slip faults result from two plates moving horizontally in opposite directions (ex: San Andreas Fault, California).
Page-size map on next page for World Tectonic Map Activity
The TOTLE Picture
Teac
hers on the Leading Edge
Earthquakes Volcanoes Tsunamis
. ..
SY
MB
OL
S
Wh
ite
arro
ws
sho
w p
late
mo
tio
n d
irec
tio
n
Volc
ano
es (g
ener
aliz
ed)
Ho
t sp
ot
(arr
ow
= d
irec
tio
n o
f pla
te m
oti
on
)
Gre
at e
arth
qu
akes
sin
ce 1
900;
bef
ore
190
0
Div
erge
nt m
argi
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Conv
erge
nt m
argi
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Tran
sfo
rm fa
ult
(arr
ow
s sh
ow
rela
tive
mo
tio
n)
PL
AT
E B
OU
ND
AR
IES
Mo
st o
f th
e w
orl
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eart
hq
uak
es a
nd
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are
fo
un
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r nea
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ary
bet
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on
ic
pla
tes.
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ctio
n b
etw
een
th
e p
late
s ke
eps
them
fro
m
slid
ing.
Wh
en t
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fric
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nal
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ain
is o
verc
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he
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ud
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ly s
nap
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g fa
ult
s an
d fr
actu
res
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asin
g e
ner
gy
as e
arth
qu
akes
. Vo
lcan
oes
occ
ur a
t di
verg
ent m
argi
ns (w
her
e m
agm
a ri
ses
and
eru
pts
); at
con
verg
ent m
argi
ns (w
her
e an
oce
anic
pla
te
div
es b
enea
th a
no
ther
pla
te; m
agm
a fo
rms
in t
he
con
tin
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l pla
te a
bov
e th
e d
ivin
g o
cean
ic p
late
), an
d le
ss c
om
mo
nly
as
hot s
pots
(w
her
e m
agm
a m
elts
th
rou
gh
a p
late
, su
ch a
s H
awai
`i).