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Chapter 2

EESA06H3 Chapter Notes - Chapter 2: Paleomagnetism, Magnetometer

Environmental Science
Course Code
Nick Eyles

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January 21, 2011
Maximum of 3 in a group for the poster assignment
Mounted in the meeting place
oPeople will walk around & ask questions
Usually there is a summary, intro, discussion & end
oWhat is the point of doing this assignment?
oWhat do you want people to learn out of it?
Graded on a couple of questions & presentation
2 Types of Crust :
oOceanic Crust is denser & wants to sink down, back into the plastic
rock underneath, thats why we have oceans. Ocean floors are
always/slowly sinking
oContinental Crust is thicker, but more buoyant like an iceberg as it
floats on the mantle (less dense)
Moho = Mohorovi ic discontinuity: base of crust
Asthenosphere: means weak spear, weak hot plastic
Plate movement: Crust + Asthenosphere moving together
Maximum depth drilled: 12km deep, expensive and difficult to drill deeper
cause its hot
Deepest mine is 4km down in South Africa, diamond mine
oAny deeper is not possible: too hot
Geophysics physical principles to the
Earth quakes pros:
oThey generate energy
oCan be used to locate the location
of plates.
Faults are no more than a crack in the
Focus is where the energy is released, where the earthquake is triggered,
always underground
oDetermines how much damage happens (the depth; the deeper, the less
damage; determines the effectiveness of the earthquakes)
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oYou can measure the earthquake from the focus
Epicenter: located directly above the focus
owhere you DONT want to be!
Fault Scarp: steep slopes that was the result of the blocks moving, like cliffs
or bluffs
Seismic Risk Assessment : process that can tell how much damage
earthquakes may do
oNot all faults are dangerous, some are always moving; no harm
oBut the ones that lock; builds energy & when it slip/moves, it becomes
a dangerous earthquake
Fault Plane - (a crack) the surface in which the plates move as one
oWhen it moves, it creates energy we feel it as an earthquake
Fault Traces are the straight lines
oRiver erosion is more common in fault traces
Seismic Waves - Same faults dont always create earthquakes, animals can
sense them and people used them as warnings. they’re just constantly
moving, abrupt movements, can be divided into several types:
oBody waves because they go down through the centre of the earths
interior and across the planet
oSurface waves goes around the globes surface
Primary waves (P. Waves) also known as compressional wave, moves
like a slinky; compressed, stretched, compressed stretched.
oThe quickest, and first to arrive, moving @ 7km/sec
oGoes through liquids, the entire planet, through the core
oWe used these to map the planet
Secondary waves (S. Waves) moves a little slower, like whipping a rope
back & forth
o@ 5km/sec, they cannot go through core because they cant go through
The further you are from the focus, the greater the time lag / separation
between the P&S waves
oUse of this information: to locate where the epicenter is, how far an
earthquake was from you
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