chapter 4 layers of the earth continental drift plate tectonics deformation of earth’s crust
TRANSCRIPT
Chapter 4Chapter 4
Layers of the EarthLayers of the EarthContinental DriftContinental DriftPlate TectonicsPlate Tectonics
Deformation of Earth’s CrustDeformation of Earth’s Crust
Layers of the EarthLayers of the Earth
CrustCrust Thin, outermost layer of EarthThin, outermost layer of Earth uppermost part of lithosphereuppermost part of lithosphere
MantleMantle Layer of Earth between crust and coreLayer of Earth between crust and core
CoreCore Central, spherical part of Earth below the mantleCentral, spherical part of Earth below the mantle
CrustCrust 5 to 100 km thick5 to 100 km thick thinnest layer of Earththinnest layer of Earth
continental crustcontinental crust similar to granitesimilar to granite
oceanic crust oceanic crust similar to basaltsimilar to basalt
MantleMantle
between crust and corebetween crust and core contains most of Earth’s masscontains most of Earth’s mass
similar to olivinesimilar to olivine large amounts of iron and large amounts of iron and
magnesiummagnesium
Layers of the MantleLayers of the Mantle
LithosphereLithosphere Outermost, rigid layer of Earth Outermost, rigid layer of Earth consists of crust and rigid upper part of mantleconsists of crust and rigid upper part of mantle
AsthenosphereAsthenosphere Soft layer of mantle on which pieces of the lithosphere Soft layer of mantle on which pieces of the lithosphere
movemove
MesosphereMesosphere ““middle sphere”middle sphere” strong, lower part of mantle between asthenosphere and strong, lower part of mantle between asthenosphere and
outer coreouter core
CoreCore
extends from bottom of mantle to extends from bottom of mantle to center of Earthcenter of Earth
slightly larger than Marsslightly larger than Mars
mostly ironmostly iron small amounts of nickelsmall amounts of nickel possibly some sulfur and oxygenpossibly some sulfur and oxygen
Outer CoreOuter Core Inner CoreInner Core
liquid layer of liquid layer of Earth’s core Earth’s core
lies beneath lies beneath mantlemantle
surrounds inner surrounds inner corecore
solid, dense center solid, dense center of Earthof Earth
Tectonic PlateTectonic Plate
a piece of a piece of lithosphere lithosphere
moves around on moves around on top of thetop of the
asthenosphereasthenosphere
How do Scientists know How do Scientists know about the structure of the about the structure of the
inside of the Earth?inside of the Earth?
EarthquakesEarthquakes When an earthquake occurs, When an earthquake occurs,
seismographs measure the difference in seismographs measure the difference in arrival times of seismic waves and record arrival times of seismic waves and record them them
Seismologists use these measurements Seismologists use these measurements to calculate the density and thickness of to calculate the density and thickness of each layereach layer
Continental DriftContinental Drift
The theory that continents can drift The theory that continents can drift apart from one another and have apart from one another and have done so in the pastdone so in the past
PangeaPangea
““all earth”all earth” land mass that existed 245 million years land mass that existed 245 million years
ago made up of all of the continents put ago made up of all of the continents put togethertogether
LaurasiaLaurasia northern half of Pangea; formed 180 million years northern half of Pangea; formed 180 million years
ago when Pangea broke in halfago when Pangea broke in half GondwanaGondwana
southern half of Pangea; formed 180 million years southern half of Pangea; formed 180 million years ago when Pangea broke in halfago when Pangea broke in half
PangeaPangea
On the Sea Floor…On the Sea Floor…
Sea Floor SpreadingSea Floor Spreading The process by which The process by which
new oceanic lithosphere new oceanic lithosphere is created at mid-ocean is created at mid-ocean ridgesridges
older materials are older materials are pulled away from the pulled away from the ridgeridge
Mid-Ocean RidgeMid-Ocean Ridge a long mountain a long mountain
chain that forms on chain that forms on the ocean floor the ocean floor where tectonic where tectonic plates pull apartplates pull apart
usually extends usually extends along the center of along the center of ocean basinsocean basins
Magnetic ReversalsMagnetic Reversals
the process by the process by which the Earth’s which the Earth’s north and south north and south magnetic poles magnetic poles periodically change periodically change placesplaces
Wegener’s TheoryWegener’s Theory
What was Wegener’s theory of continental What was Wegener’s theory of continental drift?drift? The theory that continents can drift apart from The theory that continents can drift apart from
one another and have done so in the pastone another and have done so in the past
Why was Wegener’s theory not accepted Why was Wegener’s theory not accepted at first?at first? Scientists at that time did not understand what Scientists at that time did not understand what
force of nature could move continentsforce of nature could move continents
Sea Floor SpreadingSea Floor SpreadingMid-Ocean RidgesMid-Ocean Ridges
How does sea floor spreading provide a How does sea floor spreading provide a way for continents to move?way for continents to move? It forms new crust in between the places where It forms new crust in between the places where
the spreading takes placethe spreading takes place
How does new oceanic crust form at mid-How does new oceanic crust form at mid-ocean ridges?ocean ridges? As tectonic plates move away from each other, As tectonic plates move away from each other,
the sea floor spreads apart and magma rises to the sea floor spreads apart and magma rises to fill in the gap fill in the gap
This magma cools to form new crustThis magma cools to form new crust
How do magnetic reversals How do magnetic reversals provide evidence for sea-provide evidence for sea-
floor spreading?floor spreading?
The molten rock contains tiny grains of magnetic The molten rock contains tiny grains of magnetic materials which align themselves with Earth’s materials which align themselves with Earth’s current magnetic fieldcurrent magnetic field
They are “set in stone” as the molten rock cools They are “set in stone” as the molten rock cools and solidifiesand solidifies
As the sea-floor continues to spread, these rocks As the sea-floor continues to spread, these rocks are carried away from the spreading centerare carried away from the spreading center
The magnetic fields are found in bands along the The magnetic fields are found in bands along the oceanic crustoceanic crust
Plate TectonicsPlate Tectonics
The theory that states that Earth’s The theory that states that Earth’s lithosphere is divided into tectonic lithosphere is divided into tectonic plates that move around on top of plates that move around on top of the asthenospherethe asthenosphere
Convergent BoundariesConvergent Boundaries
Convergent Convergent BoundaryBoundary The boundary The boundary
between two between two colliding tectonic colliding tectonic platesplates
Subduction ZoneSubduction Zone The region where The region where
an oceanic plate an oceanic plate sinks down into the sinks down into the asthenosphere at a asthenosphere at a convergent convergent boundaryboundary
usually between usually between continental and continental and oceanic platesoceanic plates
Three Types of Three Types of Convergent BoundariesConvergent Boundaries
Continental/Continental CollisionsContinental/Continental Collisions
Continental/Oceanic CollisionsContinental/Oceanic Collisions
Oceanic/Oceanic CollisionsOceanic/Oceanic Collisions
Divergent BoundariesDivergent Boundaries
The boundary between two tectonic The boundary between two tectonic plates that are plates that are moving away moving away from from each othereach other
Transform BoundariesTransform Boundaries
The boundary between two tectonic The boundary between two tectonic plates that are plates that are sliding pastsliding past each each other other horizontallyhorizontally
What are the 3 forces What are the 3 forces thought to move tectonic thought to move tectonic
plates?plates? ConvectionConvection
Slab PullSlab Pull
Ridge PushRidge Push
ConvectionConvection
Hot material from deep with in Earth Hot material from deep with in Earth rises while cooler material near the rises while cooler material near the surface sinkssurface sinks
As warmer material cools, it becomes As warmer material cools, it becomes more dense and sinksmore dense and sinks
The motion drags tectonic plates The motion drags tectonic plates sidewayssideways
ConvectionConvection
Slab PullSlab Pull
oceanic lithosphere is denser than oceanic lithosphere is denser than the asthenospherethe asthenosphere
the edge of the oceanic plate sinks the edge of the oceanic plate sinks pulls the rest of the tectonic plate pulls the rest of the tectonic plate
with itwith it
Ridge PushRidge Push
An oceanic plate sides down the An oceanic plate sides down the lithosphere-asthenosphere boundarylithosphere-asthenosphere boundary
occurs where oceanic lithosphere is occurs where oceanic lithosphere is higherhigher than continental lithosphere than continental lithosphere
Measuring Plate Measuring Plate MovementMovement
using a network of satellites called using a network of satellites called the Global Positioning Systemthe Global Positioning System allows scientists to record the time it allows scientists to record the time it
takes for radio signals from a position on takes for radio signals from a position on Earth to reach the satelliteEarth to reach the satellite
by monitoring changes in this, scientists by monitoring changes in this, scientists can tell how much the plates have can tell how much the plates have movedmoved
StressStress
The amount of force per unit area The amount of force per unit area that is put on a given material that is put on a given material
DeformationDeformation the change in the shape of rock in response the change in the shape of rock in response
to stress appliedto stress applied
CompressionCompression TensionTension The type of stress The type of stress
that occurs when that occurs when an object is an object is squeezedsqueezed
The type of stress The type of stress that occurs when that occurs when forces act to forces act to stretchstretch an object an object
FaultFault
A break in the Earth’s crust along A break in the Earth’s crust along which blocks of the crust slide which blocks of the crust slide relative to one another due to relative to one another due to tectonic forcestectonic forces
Types of FaultsTypes of Faults
Normal FaultNormal Fault a fault in which the hanging wall moves down relative to a fault in which the hanging wall moves down relative to
the footwallthe footwall Reverse FaultReverse Fault
a fault in which the hanging wall moves up relative to a fault in which the hanging wall moves up relative to the footwallthe footwall
Strike-slip FaultStrike-slip Fault a fault in which the two fault blocks move past each a fault in which the two fault blocks move past each
other horizontallyother horizontally
Fault BlockFault Block The blocks of crust on each side of the faultThe blocks of crust on each side of the fault
FoldingFolding
The bending of rock layers due to The bending of rock layers due to stress in the Earth’s cruststress in the Earth’s crust
Types of MountainsTypes of Mountains
Folded Folded
Fault-BlockFault-Block
Volcanic MountainsVolcanic Mountains
Folded MountainsFolded Mountains
form when rock layers are squeezed form when rock layers are squeezed together and pushed upwardtogether and pushed upward
example: example: Appalachian MountainsAppalachian Mountains
Fault Block MountainsFault Block Mountains
where tectonic forces put enough tension where tectonic forces put enough tension on the Earth’s crust, a large number of on the Earth’s crust, a large number of normal faults can resultnormal faults can result
this faulting causes large blocks of Earth’s this faulting causes large blocks of Earth’s crust to drop down relative to other blockcrust to drop down relative to other block
example:example: The Tetons (in western Wyoming)The Tetons (in western Wyoming)
Volcanic MountainsVolcanic Mountains
when molten rock erupts onto the when molten rock erupts onto the Earth’s surfaceEarth’s surface
examples: examples: Ring of FireRing of Fire Mount St. Helen’sMount St. Helen’s