LECTURE                      THE STRUCTURE OF THE EARTH

In this lecture you will:

Earthquakes were used to determine the layers by REFRACTION due to DENSITY

-- seismic waves generated during earthquakes provide info about  the interior of the earth

they reflect and change direction at boundaries between layers (like light changes direction in glass)

-- some regions don't carry waves because they are liquid.
 

http://www.thetech.org/exhibits_events/online/quakes/inside/core.html

CORE 

inner .... almost pure iron. .. solid due to pressure
outer .... liquid iron containing nickel and other impurities.
http://www.solarviews.com/eng/earthint.htm

How the earths core acts as magnet. Not as simple as "its iron"
http://www.sciencenews.org/sn_arc99/11_13_99/fob5.htm

MANTLE

-- the upper part of the mantle is composed of  viscoelastic material.  It acts like a solid when hit with seismic waves,  but it will flow under forces maintained for a long time.
heat moves up thru the mantle by convection
--  It is not uniform
-- The crust rides on this slow flowing material.

CRUST

-- thin about 5 miles under the oceans and 10 to 30 miles under the continents.
floating on the upper mantle much as an iceberg floating on water.
-- Where the crust rises high in mountains, it must also extend deeper to maintain equilibrium, just like an iceberg.
it is not uniform
-- During the ice ages the weight of the glaciers pushed the crust down, and when the ice melted the crust started rising and still is today

REVIEW QUESTIONS:

Why does the crust of Earth "ride" or float on top of the mantle?
CORE
MANTLE
CRUST

Which part of the Earth's structure is responsible for its
magnetic properties?
Which part of the Earth's structure is essential for plate
tectonics to occur? Why do the plates move?
Is the crust the same depth everywhere