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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 ________
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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!
Pangaea ___________ 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’.
Today’s Continents 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.
The crust and lithosphere are broken up into 25 ________ USGS
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
Materials 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. More Evidence:Mantle Convection
Mantle Convection 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 ______________
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
2 Ridge-Push 1 Mechanisms of Plate Tectonics: Mantle 3 drag convective flow of mantle
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. Sea Floor Spreading
Types of Boundaries • __________ • __________ • __________
A Divergent B Convergent C Sliding • 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 __________
A Divergent B Convergent C Sliding Continental crust ___________ Oceanic crust ___________________ 2 continental plates __________________ Plates move against each other Stress builds up Stress is released ____________ 2 oceanic plates or oceanic + continental _________
Sea floor spreading, leads to _________________ DIVERGENCE: Sea Floor Spreading *This hypothesis makes a number of testable predictions.*
Magnetic Reversals Interestingly, 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. We are apparently headed into a polarity reversal, to be complete in ~3000 yr. * Taking magnetic stratigraphy back in time is paleomagnetism. *
The _____________ as products of steady creation of ____ ocean crust over geologic time. Paleomagnetism and Sea Floor Spreading
The ridge is a ___________ Plate Margin and divergence takes place by __________________. New crust is added from upwelling __________ (molten rock) from the upper ___________. From http://www.uwsp.edu/geo/faculty/ritter/glossary/s_u/sea_flr_spread.html Older crust is pushed laterally away from the ridge axis – so that the sea floor spreads away from the ridge axis.
CONVERGENCE: Oceanic Crust – Continental Crust The __________ oceanic crust descends beneath lighter continental crust. __________________ develop due to compressive forces and volcanics (e.g., the Andes of South America). Magma material rises from descending slab and builds _____________ in the rising mountains.
CONVERGENCE: Oceanic Crust-Oceanic Crust The ________, _________ crust normally descends beneath the younger crust. ______________ develop at the surface of the over-riding crust (forming Island Arcs) - e.g ___________
CONVERGENCE: Continental Crust-Continental Crust Neither plate __________ (both too light). Compressive forces driving plates fold and thrust the continental margins forming an _______________________ belt (e.g., the Himalayan Mountains).
SLIDING: Slip-Strike Faults 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.
