Layers of the Earth
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Transcript of Layers of the Earth
Layers of the Earth
CRUST/LITHOSPHERE
• _________ layer- is cool and ________- between ______ km thick
• __________ on mantle• Oceanic Crust: ________ thick• Continental Crust ~ ________ thick
Mantle/Athenosphere
• average thickness is about _________km• solid but ________• behaves like ________, flowing and
circulating slowly without breaking
Core
• radius ~ ________ km• half of the Earth’s diameter • metallic - made of _____ and ________• outer core - ________• inner core -________
Supercontinent
Pangea – _______• Similar _____ and ______
• _____ forests• _____ deposits
Tens of Millions of years ago!
___________ revived the early idea of _____________, contending that all of the present-day continents were connected,
side-by-side, as long ago as the Carboniferous (~300 Myr).
He called the supercontinental mass ___________, Greek for ‘all lands’.
Pangaea
As soon as maps of the globe became available, people wondered about the arrangement of the continents and oceans. Hundreds of years later, valid explanations were constructed.
Today’s Continents
USGS
The crust and lithosphere are broken up into 25 ________
Movement of the Plates:_________________
• Evidence• How it works
Continental Drift: Fossil Evidence
Mesosaurus: _________________Glossopteris: _______________________________________
Continental Drift: Rock Ages
Rock ages showed strong correlation across the ___________, as did mountain ranges of similar age.
Continental Drift: Geometry evidence
• shape of the continents• eg. the shape of the west coast of
_________ and the east coast of ______________ are remarkably similar and were perhaps once joined
More Evidence:Mantle ConvectionMaterials that can flow
tend to lose
_____________ by the
convection process. This
explains circulation in a pot
of water that is being
heated from below in the
same way it describes the
________________ in the
Earth’s mantle.
Giant convection cells within the upper mantle drag the plates along laterally.
Where convection rises ________________ takes place.
Where the convection cells descend they drag crust down, causing ______________
Mantle Convection
How does it work?_________ – pieces of the lithosphere
Plates fit closely together along cracks called
_______________
Convection Currents ______________
Here is another version of the Rock Cycle
http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Metrocks/Metrocks2.html
Mechanisms of Plate Tectonics:
Mechanisms of Plate Tectonics:
Ridge-Push
Mantledrag
convective flow of mantle
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Sea Floor Spreading
Hot material rose at the ______________, thus explaining the
high heat flow and volcanic activity, and why the ocean floor is
bulged up at the ridges.
The logical next step is that where continent and ocean meet, at
the __________, ocean crust is being returned to the mantle at
the same rate it is being generated at the ridges.
Types of Boundaries
• __________
• __________
• __________
To summarize……
CSliding
BConvergent
ADivergent
• plates are __________
• new crust is created
• ______ is coming to the surface
• plates are ___________
• crust is returning to the __________
• plates are __________ each other
• crust is not ________ or __________
Plates move against each other
Stress builds up
Stress is released ____________
2 continental plates __________________
Continental crust ___________
Oceanic crust ___________________
CSliding
BConvergent
ADivergent
2 oceanic plates oroceanic + continental _________
DIVERGENCE: Sea Floor SpreadingSea floor spreading, leads to _________________
*This hypothesis makes a number of
testable predictions.*
Magnetic ReversalsInterestingly, the polarity of the magnetic field shifts every 0.5 - 1.0 Myr. That means rocks formed over time will record either ‘_________’ magnetic orientation (like today), or ‘_________’. This leads to alternating bands of normal and reversed magnetism.
* Taking magnetic stratigraphy back in time is paleomagnetism. *
We are apparently headed into a
polarity reversal, to be complete in
~3000 yr.
The _____________ as products of
steady creation of ____ ocean crust
over geologic time.
Paleomagnetism and
Sea Floor Spreading
Oceanic Ridges
The ridge is a ___________ Plate Margin and divergence takes place by __________________.
From http://www.uwsp.edu/geo/faculty/ritter/glossary/s_u/sea_flr_spread.html
New crust is added from upwelling __________ (molten rock) from the upper ___________.
Older crust is pushed laterally away from the ridge axis – so that the sea floor spreads away from the ridge axis.
Magma material rises from descending slab and builds _____________ in the rising mountains.
__________________ develop due to compressive forces and volcanics (e.g., the Andes of South America).
CONVERGENCE: Oceanic Crust – Continental CrustThe __________ oceanic crust descends beneath lighter continental crust.
CONVERGENCE: Oceanic Crust-Oceanic Crust
______________ develop at the surface of the over-riding crust (forming Island Arcs) - e.g ___________
The ________, _________ crust normally descends beneath the younger crust.
CONVERGENCE: Continental Crust-Continental Crust
Compressive forces driving plates fold and thrust the continental margins forming an _______________________ belt (e.g., the Himalayan Mountains).
Neither plate __________ (both too light).
Plate __________ along which the plates slip by each other. Termed: Slip-Strike Faults/Transform Faults
On either side of a fault plate motions are in __________ directions.
SLIDING: Slip-Strike Faults
The Big Picture