Chapter 9 and 10 The interior of the earth and its surface.

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