Upload
prosper-ryan
View
218
Download
1
Tags:
Embed Size (px)
Citation preview
Plate TectonicsPlate Tectonics
DefinitionDefinition
Plate: Tectonic:
Rigid, rocky outer surface of the Earth
To build or destroy
The processes by which the rocky plates of the planet move
and interact with each other
Internal Structure of the EarthInternal Structure of the Earth
lithosphere
mantle
inner core
outer core
plates
solid iron
hot dense rock
liquid iron
Lithospheric PlatesLithospheric PlatesOceanic:
thin, heavy, mostly lava flows
Continental:
thick, light, mostly granite
Asthenosphere
Weak, plastic upper mantle
Lithospheric PlatesLithospheric Plates
Diverging Plate BoundariesDiverging Plate BoundariesWhere plates pull apart from each other
Stretching & thinning
High heat flow
(New Crust Created)
Diverging Plate BoundariesDiverging Plate BoundariesKey landform: mid-oceanic ridges
volcanic mt. ranges
1000’s miles long
1-2 miles tall
axial valley
Converging Plate BoundariesConverging Plate Boundaries
Where plates collide
Subduction zone: collision between oceanic and continental lithosphere
(Crust Destroyed)
Subduction zonesSubduction zonesKey landforms:
trenches & volcanic arcs
Transform Plate BoundariesTransform Plate Boundaries
Where plates slide side by side
Key landform: faults
(Crust neither destroyed or created)
Driving ForceDriving Forcethermal convection / convection currents
hot rock
plates spread away
cold rock
pushes up at ridges
plate sinks and subducts
Volcanism: C, D
Earthquakes: C, D, T
Rock Deformation: C, D, T
Geologic activity at plate marginsGeologic activity at plate margins
Evidence: shape of continentsEvidence: shape of continents
SouthAmerica
Africa
The margins of some continents
look like they could fit together
First proposed by Alfred Wegner
Fossil EvidenceFossil Evidence
Evidence: volcanoesEvidence: volcanoes
Nonrandom occurrence of volcanic activity
Evidence: earthquakesEvidence: earthquakes
x xx
x xx
xx x
x
Nonrandom occurrence of earthquakes
deep at converging margins
Shallow at diverging margins
Evidence: hot spotsEvidence: hot spotsStationary upwellings of heat away
from plate margins
Evidence: hot spotsEvidence: hot spots
As plates move, the volcanoes are carried away from the hot spot
Can determine direction and speed of the plate motion
Only volcanoes near the hot spot are are active
Evidence: age of seafloor rocksEvidence: age of seafloor rocks
Youngest rocks are found at the mid oceanic ridges
Oldest rock are found farthest from the ridge
Evidence: paleomagnetismEvidence: paleomagnetism
Earth has a strong magnetic field
Iron rich volcanic rocks record Earth’s magnetic field at the time
they form
seafloor paleomagnetic recordseafloor paleomagnetic record
Bands of alternating polarity
Symmetrical about the mid oceanic ridges
seafloor paleomagnetic recordseafloor paleomagnetic record
lava forming at the ridges picks up the current magnetism, then gets pushed out
of the way as newer lava forms
Records of the growth and spreading of the
seafloor
seafloor paleomagnetic recordseafloor paleomagnetic record
The alternating polarity represents complete reversals of Earth’s
magnetic field
The location of magnetic poles on The location of magnetic poles on separate continents appear to wander separate continents appear to wander
with timewith time
continental paleomagnetic recordcontinental paleomagnetic record
If the poles haven’t moved significantly, then the continents
didUse overlapping poles to reconstruct the past positions of the continents
Plate Tectonics in the PNWPlate Tectonics in the PNW
0 20 0
k m
M t M e a g e r
M t C ay le y
M t G ar ib al d i
M t B ak er
G la cie r P ea k
M t R ai n ier
M t A d a m sM t S t H e l e n s
M t H o o d
M t J e f fe rs o n
T h r e eS is te r s
C ra ter L a ke
M t M c L o u g h in
M t S h as ta
L as s e n P e ak
Sa n
And
reasFa ul t
Juan
deFu
caNorth American
Pacific
Cascadia subduction
zone
Plate Tectonics in the PNWPlate Tectonics in the PNW
HighCascadesvolcanoes Western
CascadesWillamette valley
CoastRange
Deschutes basin
ocean
subducting oceanic plate
partialmelting
60 miles
150 milesWest East
Pacific
Cross section of the Cascadia Subduction zone
Cascades volcanic arc
Plate Tectonics in the PNWPlate Tectonics in the PNW
0 20 0
k m
M t M e a g e r
M t C ay le y
M t G ar ib al d i
M t B ak er
G la cie r P ea k
M t R ai n ier
M t A d a m sM t S t H e l e n s
M t H o o d
M t J e f fe rs o n
T h r e eS is te r s
C ra ter L a ke
M t M c L o u g h in
M t S h as ta
L as s e n P e ak
Sa n
And reas
Fa ul t
Juan
deFu
caNorth American
Pacific
Juan de Fuca & Gorda mid ocean
ridges
Plate Tectonics in the PNWPlate Tectonics in the PNW
0 20 0
k m
M t M e a g e r
M t C ay le y
M t G ar ib al d i
M t B ak er
G la cie r P ea k
M t R ai n ier
M t A d a m sM t S t H e l e n s
M t H o o d
M t J e f fe rs o n
T h r e eS is te r s
C ra ter L a ke
M t M c L o u g h in
M t S h as ta
L as s e n P e ak
Sa n
An
d reasFa ul t
Juan
deFuca
North American
Pacific
Blanco & Medocino
fracture zones
Plate Tectonics in the PNWPlate Tectonics in the PNW
“exotic terranes
islands carried by the plates
Attached to the North America continent
seafloor paleomagnetic recordseafloor paleomagnetic record
Bands of alternating polarity
Symmetrical about the mid oceanic ridges
Evidence: paleo-environmentsEvidence: paleo-environments
deserts
glacial
coral reefs
deserts
glacial
desert
desert
glacial
tropics
Evidence: distribution of mountainsEvidence: distribution of mountains
Importance of Plate TectonicsImportance of Plate Tectonics