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

21

3

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