chapter 9 and 10 the interior of the earth and its surface
TRANSCRIPT
Chapter 9 and 10
The interior of the earth
and it’s surface
The Interior of the EarthWe can’t go thereUse the shock waves an earthquake
makes to investigate it.Called seismic wavesTwo types
– S waves (sheer waves)– P waves (pressure waves)
Measured with a seismograph
Seismograph
Heavy object
Drum
Seismograph
As ground shakesthe base movesbut the weight stays still
Seismic wavesPenetrate earth and return to surface.Speed and direction changeS waves can’t go through liquidsP waves can, but they slow down.As the waves go through the earth at
2900 km down, the S waves stop and the P waves slow down
At 5105 Km down the P waves speed upWhat does this tell us?
The Earth’s CoreThe center of the earthTwo layers Inner core
– Iron and Nickel– 5000º C– Pressure keeps it solid– Responsible for magnetic field?
The Earth’s CoreThe outer core
– Iron and Nickel– 2200º C to 5000º C– Not as much pressure so it is liquid
How do they knowP waves are pressure waves
– Will go through liquidS waves are sheer waves
– won’t go through liquids
S waves
Liquid
P waves
TotalShadow
No waves
The MantleAbove the outer core80% of the earth’s volume68% of the earth’s volumeStudied rocks from volcanoesHave studied rocks from the ocean floor
– Silicon, oxygen, iron, magnesiumDensity increases with depthBecause there’s more ironMeasured by speed of the seismic waves
The MantleTemperature increases with depthHas plasticityWhat is plasticity?A solid that can flow like a liquidSilly putty870º C -2200º C
The Moho the thin boundary layer between the
mantle and the crust32-64 kmDiscovered by Andrija MohorvičićFound seismic waves changed speed at
this levelEither different composition or density.
The crustThin outer layer we live on If the earth were the size of an apple, the
crust would be thinner than the peel8-32 km Two kinds
– Oceanic– Less than 10 km– all basalt- dense
The crustContinental crust
– Thicker- averages 32 km, up to 70 km– Top layer granite- less dense, on top of
dense basaltEarth’s crust also called lithosphereLithosphere broken into large plates
(called tectonic plates)
Inner Core
Outer Core
Mantle
Moho
Crust
6500km
5150 km
2900 km
32 km
0 km
Mantle
Basalt
Granite
ContinentOcean
Chapter 10
How the crust moves
Crust Continental –
– Thicker– Granite and basalt
Oceanic – Thinner– All Basalt
Stress- the pushes and pulls on the crust causes changes in the rock
– Shape– Volume
Compresses or expands Deformation- breaking, tilting, and folding of of rocks
StressThree typesCompression- pushed together
Three typesCompression- pushed togetherMoves land higher up and deeper
Stress
StressTensionPulled apartStretches like taffyThinner in the middle
TensionPulled apartStretches like taffyThinner in the middle
Stress
StressShearing- pushes in two opposite
horizontal directionsRocks are torn apart or bent
StressShearing- pushes in two opposite
horizontal directionsRocks are torn apart or bent
Stress changesShapeVolumeDensityCan cause cracks - fractureFracture along smooth surface is called a
jointJoints are parallel
FaultsA break or crack where rocks moveWhere earthquakes happenHanging wall- above the faultFoot wall- below the faultThree types of fault tension causes normal fault Compression causes reverse fault and
thrust fault
Normal faultTension pulls apartHanging wall moves down
Hanging wallFoot wall
Normal faultTension pulls apartHanging wall moves down
Reverse faultCompression pushes together the hanging wall up
Hanging wallFoot wall
Reverse faultCompression pushes together the hanging wall up
Thrust FaultCompression continues The hanging wall is pushed over the foot
wallend up with layers of rock repeatedOlder rock on top of younger rock
Thrust fault
Oldest Rock
Youngest Rock
Lateral FaultCaused by shear stressBlocks move sideways
Lateral FaultCaused by shear stressBlocks move sideways
Faulted Mountains and Valleys
A series of normal faults will cause mountains to be uplifted.
Called Fault-block mountainsSierrasValleys will also be formedCalled rift valleysDeath Valley
Fault Block Mountain
Fault Block Mountain
Rift valleys
Rift valleys
FoldingSome times rock doesn’t break It forms folds- like wrinklesUpward fold- anticlineDownward fold- synclineVary in size, from microscopic to
mountain forming
AnticlineSyncline
Why FoldWhy don’t they breakTemperature- hot rock is easier to bendPressure- higher pressure more likely to
foldType of rock- some are more brittle,
some are more malleableGradual force bends, sudden force
breaks
PlateauFlat area made of layers of flat-topped
rocks high above sea levelCan be formed like fault block mountainsOr by lava flows (lava plateau)Colorado plateau- West of the Rocky
mountains formed Grand canyonRivers cut large plateau into several
smaller ones
DomesMagma forms a bubble underneath the
crust, without eruptingHalf sphere surrounded by flat land If worn into separate peaks they are
called dome mountains
The Crust FloatsOn the mantleBecause it is less denseThe floating crust pushes downThe crust pushes up.Balance of forces called isostasyMore material floats lower
Isostasy
Mantle
Crust
Ice
Isostasy
Mantle
Crust
Ice
Isostasy
Mantle
Crust
Isostasy
Mantle
Crust
Over time depression will rise back up.
Isostasy
Continental crust
Mantle
Sediments wash offcontinents
Isostasy
Continental crust
Mantle
Sediments pile upon ocean floor
Isostasy
Continental crust
Mantle
Pushes ocean floor down