Unit III Dynamic Crust Powerpoint

Unit III: The Dynamic Unit III: The Dynamic Crust, Earthquakes and Crust, Earthquakes and

the Earth’s Interiorthe Earth’s InteriorReview Book pp.47-65Review Book pp.47-65

Taken from http://vschsd.org/schools/central/sciencecentral/finellis_web/m1.jpgon 8/15/06

Objective #1Objective #1 Why is the Earth’s crust described as Why is the Earth’s crust described as

being dynamic?being dynamic?Animationshttp://www.pbs.org/wnet/savageearth/animations/index.html

Crust- solid rock outer zone of Crust- solid rock outer zone of EarthEarth

The crust is part of the The crust is part of the lithospherelithosphere.. The Earth’s crust is dynamic which means The Earth’s crust is dynamic which means

constantly changing.constantly changing.

Some of these changes can be directly observed such as the results of:

Taken from http://www.physicalgeography.net/fundamentals/10h.html on 8/18/06

EarthquakesEarthquakes

Taken from http://cse.ssl.berkeley.edu/img/earthquakes/Railroad.gif on 8/15/06

An apartment building in San Francisco’s Marina District shows heavy damage from a 1989 earthquake.

Taken from http://www.nationalgeographic.com/eye/earthquakes/ images/earthquakes_intro_image.gif on 8/15/06

VolcanoesVolcanoes

Mount St. Helens shortly after the eruption of May 18, 1980

Taken from http://en.wikipedia.org/wiki/Volcano on 8/15/06Taken from http://library.advanced.org/17457/volcanoesdb/images/240/v5p42x240.jpg on 8/15/06

Eruption of Mt. Arenal, Costa Rica

Crustal movements along fault Crustal movements along fault zoneszones

Both images taken from http://library.thinkquest.org/C003603/english/earthquakes/multimedia.shtml on 8/15/06

Other evidence indicates that Other evidence indicates that parts of the Earth’s crust have parts of the Earth’s crust have

been moving to different locations been moving to different locations for for billionsbillions of years. of years.

Objective #2Objective #2

Describe 7 pieces of evidence that Describe 7 pieces of evidence that suggest minor changes in the Earth’s suggest minor changes in the Earth’s crust.crust.

a) Displaced & Deformed Rock a) Displaced & Deformed Rock Strata and FossilsStrata and Fossils

Sedimentary rocks Sedimentary rocks appear to form in appear to form in horizontalhorizontal layers. layers. However, However, observations of the observations of the Earth’s surface Earth’s surface indicate that the indicate that the original formations original formations of rock have of rock have changed changed through through past movements.past movements.

TiltingTilting

Earth movement Earth movement resulting in a resulting in a change in the change in the position of rock position of rock layers,layers,

“ “rocks at an rocks at an angle”angle”

Folded StrataFolded Strata Bend in the rock layers produced during Bend in the rock layers produced during

the mountain building processthe mountain building process

FaultingFaulting Movement of rock along a crack (fault) in Movement of rock along a crack (fault) in

the crustthe crust

b) Displaced Fossilsb) Displaced Fossils Displaced means Displaced means

“moved.”“moved.” Marine fossils- Marine fossils-

remains or imprints remains or imprints of once living of once living ocean organisms ocean organisms such as coral, fish, such as coral, fish, etc. found in etc. found in sedimentary rocksedimentary rock

? Where would you expect to find marine fossils?

Taken from http://orerockon.com/coal_ck5.jpgon 8/18/06

Marine fossils found in layers of Marine fossils found in layers of sedimentarysedimentary rock in mountains, often rock in mountains, often thousands of feet above thousands of feet above sea levelsea level. .

These marine fossils found at high These marine fossils found at high elevation suggest elevation suggest past uplift of rock strata.past uplift of rock strata.

Marine Fossils on Top of the Andes Mountains. More than 500 giant fossilized oysters were found 3000 meters (about 2 miles) above sea level in Peru in 2001

Taken from http://antiquity.ac.uk/ProjGall/jeck/images/fig1.jpg on 8/18/06

c) Subsidencec) Subsidence Sinking or settling Sinking or settling

of rock strataof rock strata

Taken from http://geochange.er.usgs.gov/sw/changes/anthropogenic/subside/fig0.jpg on 8/18/06

Example: finding Example: finding fossils of shallow fossils of shallow water organisms in water organisms in rocks found deep in rocks found deep in ocean floor.ocean floor.

Early in the 20th Century, land near the Alviso Marina in Santa Clara, CA, top, sank nearly 13 feet due to overpumping of local groundwater, below

Taken from http://www.valleywater.org/media/Alviso_subsidence.jpg on 8/18/06

d) Displaced Stratad) Displaced Strata Rock layers that have been moved.Rock layers that have been moved.

Horizontal Displacement Horizontal Displacement (Faulting)(Faulting)

Earth shifts Earth shifts sideways along a sideways along a transform fault in transform fault in the crustthe crust

The fence was offset 2.6 m by the magnitude 8.2 earthquake of April 18, 1906, San Francisco, California, a section of the San

Andreas fault.

Both images taken from http://www.ngdc.noaa.gov/seg/hazard/slideset/10/10_slides.shtml on 8/15/06

Offset of a cement-lined ditch by the Motagua fault resulting from the earthquake of February 4, 1976, in Guatemala.

Vertical Displacement Vertical Displacement (Faulting)(Faulting)

Portion of Earth’s Portion of Earth’s surface is either surface is either uplifted or subsides uplifted or subsides along a fault or along a fault or crack.crack.

Taken from http://www.rcep.dpri.kyoto-u.ac.jp/~sato/taiwan/twpics/tw/tw004.JPG on 8/18/06

Collapsed bridge and waterfall created by vertical faulting on river northeast of Fengyuen in Taiwan

BenchmarkBenchmark

Permanent cement or brass marker in Permanent cement or brass marker in ground indicating a measured elevation.ground indicating a measured elevation.

Taken from http://www.adirondackjourney.com/images/Great_Range/Benchmark%20on%20Gothics.jpg on 8/18/06

Brass benchmark: Summit of Gothics Mountain in Adirondacks

e) Isostasye) Isostasy Condition of balance Condition of balance

or equilibrium in or equilibrium in Earth’s crust.Earth’s crust.

Since the upper Since the upper mantle acts like a mantle acts like a very dense fluid, the very dense fluid, the crustal plates crustal plates floatfloat on top of it.on top of it.

Any change in one part Any change in one part of the crust is offset by of the crust is offset by a corresponding a corresponding changechange in another part of the in another part of the crust.crust.

Photo of baby on waterbed taken from http://thepeacock.com/Spiritual/Photo_of_Baby_Jennifer_on_Waterbed_for_Why_were_we_Born.jpg on 8/18/06

Taken from http://www.platetectonics.com/book /images/Convection.gif on 8/18/06

Example of IsostasyExample of Isostasy If a piece of crust If a piece of crust

loses some of its loses some of its material due to material due to erosion, it becomes erosion, it becomes lighterlighter and floats and floats higherhigher in the in the mantle. When the mantle. When the eroded material eroded material gets deposited, the gets deposited, the crust is weighted crust is weighted down causing that down causing that area to area to sinksink lower lower into the mantle.into the mantle.

Taken from http://tlacaelel.igeofcu.unam.mx/~GeoD/isostasy/figs/isost4.jpg on 8/18/06

Another isostatic example.Another isostatic example. Occurred in NYS and Occurred in NYS and

created seismic created seismic activity. The deposition activity. The deposition of 2 miles thick ice on of 2 miles thick ice on NY during a glacial ice NY during a glacial ice age caused the area to age caused the area to subsidesubside slightly. This slightly. This forced other areas to forced other areas to rise rise higherhigher in response in response to the settling under to the settling under the ice. Later after the the ice. Later after the ice receded or melted, ice receded or melted, the region responded the region responded with gradual with gradual upliftuplift causing minor seismic causing minor seismic activity or activity or earthquakes.earthquakes.


Give examples of crustal activity and Give examples of crustal activity and explain where the zones of crustal explain where the zones of crustal activity are located. (ESRT p.5)activity are located. (ESRT p.5)

II. Areas of Crustal ActivityII. Areas of Crustal Activity Crustal activities such as Crustal activities such as earthquakesearthquakes and and

volcanoes volcanoes occur for the most part in specific occur for the most part in specific zones or regions of the Earth.zones or regions of the Earth.

These regions are usually along the borders These regions are usually along the borders of of continentscontinents and and oceansoceans. These zones . These zones mark boundaries or edges of large pieces of mark boundaries or edges of large pieces of the Earth’s crust called the Earth’s crust called crustal boundaries.crustal boundaries.

ESRT p.5ESRT p.5


What is an earthquake? Explain the What is an earthquake? Explain the difference between an epicenter and difference between an epicenter and a focus of an earthquake.a focus of an earthquake.

Objective #5Objective #5Describe properties of the 3 types of Describe properties of the 3 types of earthquake waves and tell the earthquake waves and tell the difference between a seismograph difference between a seismograph and a seismogram.and a seismogram.

I. EarthquakesI. Earthquakes

Sudden trembling Sudden trembling or shaking of or shaking of ground usually ground usually caused by caused by movement along a movement along a break or a fault break or a fault releasing built up releasing built up stressstress

When an earthquake When an earthquake occurs, occurs, seismicseismic waves waves are created and move are created and move out in all directions out in all directions from the from the focusfocus or point or point of origin.of origin.

The earthquake’s focus The earthquake’s focus or or point of originpoint of origin is is usually deep below the usually deep below the Earth’sEarth’s surface. surface.

The point on the The point on the Earth’s surface directly Earth’s surface directly above the focus is above the focus is called the called the epicenter.epicenter.


Describe properties of the 3 types of Describe properties of the 3 types of earthquake waves and tell the earthquake waves and tell the difference between a seismograph difference between a seismograph and a seismogram.and a seismogram.

II. Earthquake WavesII. Earthquake Waves Seismograph: Seismograph:

Instrument that Instrument that detects and detects and records seismic records seismic waves.waves.

Earthquakes Earthquakes generate several generate several kinds of kinds of seismicseismic waves that can waves that can be detected by a be detected by a seismograph.seismograph.

3 types of 3 types of seismic waves seismic waves are are pp, , ss, & , & ll waves.waves.

L wavesL waves

Long wavesLong waves Do not pass through the Earth.Do not pass through the Earth. Ripple along the Ripple along the surfacesurface of the Earth of the Earth Create the damage associated with Create the damage associated with

earthquakesearthquakes

P wavesP waves

PrimaryPrimary waves waves Also called Also called compressionalcompressional because because they cause the they cause the

material through which they pass to vibrate back and material through which they pass to vibrate back and forth (compress) in the same direction as the wave is forth (compress) in the same direction as the wave is traveling.traveling.

Called primary because they move quickly through Called primary because they move quickly through the Earth with a greater the Earth with a greater velocityvelocity than secondary than secondary waves and therefore are the first waves to reach a waves and therefore are the first waves to reach a distant location.distant location.

Taken from http://www.lamit.ro/images/earthquake-p-waves-passage.jpg on 8/18/06

S wavesS waves

SecondarySecondary waves waves Also called Also called shearshear waves because waves because they they

cause the material through which they pass cause the material through which they pass to vibrate at right angles (up & down) to to vibrate at right angles (up & down) to the direction in which the wave is travelingthe direction in which the wave is traveling

Taken from http://www.lamit.ro/images/earthquake-s-waves-passage.jpg on 8/18/06

http://www.thetech.org/exhibits_events/online/quakes/waves/p&s_waves.html

III. Velocities of WavesIII. Velocities of Waves When traveling in the same material, When traveling in the same material,

primary waves travel at a greater primary waves travel at a greater velocityvelocity than than secondarysecondary waves. So a seismograph waves. So a seismograph will read the will read the primaryprimary waves before the waves before the secondarysecondary waves arrive. waves arrive.

Waves rock house animation

A single seismogram showing the arrival times A single seismogram showing the arrival times of p & s waves may be used to determine the of p & s waves may be used to determine the distancedistance to the earthquake and its time of to the earthquake and its time of originorigin..

The greater the difference in arrival times of The greater the difference in arrival times of the primary and secondary waves, the the primary and secondary waves, the greatergreater the distance to the earthquake the distance to the earthquake epicenterepicenter..

Eureka, CA seismogram of earthquake

Elko, NV seismogram of earthquake

Both seismograms taken from http://www.sciencecourseware.org/VirtualEarthquake/php/Seismograms.php on 8/18/06

Animation showing waves arriving at seismograph


From a seismogram, be able to find From a seismogram, be able to find the distance to epicenter, origin time the distance to epicenter, origin time and epicenter location by using ESRT and epicenter location by using ESRT p.11.p.11.

a) Finding the Distance to an a) Finding the Distance to an Earthquake’s EpicenterEarthquake’s Epicenter

To find out how far an epicenter was away To find out how far an epicenter was away from a location, a seismograph reading or from a location, a seismograph reading or seismogram seismogram is necessary that shows the is necessary that shows the arrival of both arrival of both pp and and ss waves. waves.

Then follow 4 steps using the Earthquake Then follow 4 steps using the Earthquake Graph in the ESRT on page Graph in the ESRT on page 1111..

Taken from http://upload.wikimedia.org/wikipedia/id/a/a6/Seismogram.gif on 8/18/06

4 Steps for Finding Epicenter 4 Steps for Finding Epicenter DistanceDistance

1)1) Calculate the difference between p Calculate the difference between p and s arrival times.and s arrival times.

2)2) Using the y-axis of the graph, mark Using the y-axis of the graph, mark the time difference between p and s the time difference between p and s waves on a scrap edge of paper.waves on a scrap edge of paper.

3)3) Take the scrap edge and find the gap Take the scrap edge and find the gap between the p and s waves on graph between the p and s waves on graph that equals the time difference.that equals the time difference.

4)4) Follow the scrap edge from gap Follow the scrap edge from gap straight down to the epicenter straight down to the epicenter distance.distance.

Let’s Do an Example following the 4 Let’s Do an Example following the 4 stepssteps ESRT p.11ESRT p.11

b) Calculating the Origin Time of an b) Calculating the Origin Time of an EarthquakeEarthquake

Use ESRT p.11Use ESRT p.11

1)1) Find the epicenter distance on the x-axis Find the epicenter distance on the x-axis & go straight up to the p wave graph & go straight up to the p wave graph line.line.

2)2) Take that point on the p graph line & go Take that point on the p graph line & go straight across to the time it takes a p straight across to the time it takes a p wave to go that distance (y-axis).wave to go that distance (y-axis).

3)3) Take the p travel time you just found & Take the p travel time you just found & subtract it from the time the p wave subtract it from the time the p wave arrived to get the origin time.arrived to get the origin time.

Let’s Do an Example following the 3 Let’s Do an Example following the 3 stepssteps ESRT p.11ESRT p.11

c) Determining the Exact c) Determining the Exact Location of an Earthquake’s Location of an Earthquake’s

EpicenterEpicenter Epicenter location is Epicenter location is

found by the found by the comparison of comparison of differences in travel differences in travel time of time of pp & & ss seismic seismic waves. waves.

Knowing the separation Knowing the separation time between arrival of time between arrival of both p & s waves gives both p & s waves gives the distance to the the distance to the point on the Earth’s point on the Earth’s surface directly above surface directly above the earthquake called the earthquake called the the epicenter.epicenter.

Taken from http://www.stkc.go.th/LOEarthScience/OFFLINE/LO504/1_en.htm on 8/18/06

Taken from http://www.worsleyschool.net/science/files/earthquake/epicentre.html on 8/18/06

Since only the Since only the distancedistance to epicenter and not to epicenter and not direction is known, a direction is known, a circle is drawn with the circle is drawn with the radius equal to the radius equal to the distance.distance.

The epicenter is on the The epicenter is on the circle.circle.

To find the actual To find the actual location of the location of the epicenterepicenter you must you must find the distance from find the distance from 33 different different seismograph stations. seismograph stations. Why not 2?Why not 2?

Images taken from http://www.worsleyschool.net/science/files/earthquake/epicentre.html on 8/18/06

Draw Draw 33 circles around circles around the the 3 3 seismograph seismograph stations and where stations and where they intersect is the they intersect is the earthquake’s earthquake’s epicenter.epicenter.

The earthquake The earthquake occurred at a point occurred at a point somewhere below the somewhere below the epicenter and that epicenter and that internal point is called internal point is called the the focus.focus.

Scientists wanting to Scientists wanting to improve accuracy of improve accuracy of finding the true finding the true epicenter will find the epicenter will find the distance from distance from moremore than 3 seismograph than 3 seismograph stations.stations.

Try these exercises on the computer with Virtual Earthquake!

Review animation


Compare and contrast the 2 scales Compare and contrast the 2 scales for determining the strength of an for determining the strength of an earthquake.earthquake.

a) The Modified Mercalli Scalea) The Modified Mercalli Scale

Based upon the Based upon the damage inflicted damage inflicted by an earthquake.by an earthquake.

This This intensityintensity scale scale ranges from I to XII ranges from I to XII with I being felt by with I being felt by few peoplefew people to XII to XII resulting in resulting in total total devastationdevastation..

Taken from http://data.gns.cri.nz/geoatlas/images/mercalli.jpg on 8/18/06

Modified Mercalli Scale Modified Mercalli Scale ContinuedContinued

Although this scale Although this scale is still used, it is not is still used, it is not very precise. Why?very precise. Why?

Damage inflicted by Damage inflicted by earthquakes earthquakes depends on many depends on many factors besides the factors besides the strength of the strength of the earthquake such as earthquake such as location, type of location, type of land, building land, building design & structure, design & structure, etc.etc.

Taken from http://www.ericandsylvia.com/pictures/2000/11-25-2000/cvt/img_4538.jpg on 8/18/06

The building that has straps on it is supposed to be very earthquake proof, because the straps hold the building suspended on a central cement column.

Alaskan tundra in fall foliage

Taken from http://www.galleryone.com/images/cook/cook_-_alaska_tundra_in_autumn_glory_denali_highway_central_alaska.jpg on 8/18/06

b) The Richter Scaleb) The Richter Scale A A MagnitudeMagnitude scale scale

used to describe the used to describe the amount of amount of energyenergy released by an released by an earthquake. earthquake.

Richter scale Richter scale magnitudes range magnitudes range from from 0 0 to to 9.9.

Each number step up Each number step up the scale indicates a the scale indicates a release of release of 3232 times times more energy than the more energy than the previous step.previous step.

Richter Approximate TNT for Example

Magnitude Seismic Energy Yield

0.5 5.6 kg (12.4 lb) Hand grenade

1 32 kg (70 lb) Construction site blast

1.5 178 kg (392 lb) WWII conventional bombs

2 1 metric ton late WWII conventional bombs

2.5 5.6 metric tons WWII blockbuster bomb

3 32 metric tons Massive Ordnance Air Blast bomb

3.5 178 metric tons Chernobyl nuclear disaster, 1986

4 1 kiloton Small atomic bomb

4.5 5.6 kilotons Average tornado (total energy)

5 32 kiloton Nagasaki atomic bomb

5.5 178 kilotons Little Skull Mtn., NV Quake, 1992

6 1 megaton Double Spring Flat, NV Quake, 1994

6.5 5.6 megatons Northridge quake, 1994

7 32 megatons Largest thermonuclear weapon

7.5 178 megatons Landers, CA Quake, 1992

8 1 gigaton San Francisco, CA Quake, 1906

8.5 5.6 gigatons Anchorage, AK Quake, 1964

9 32 gigatons 2004 Indian Ocean earthquake

10 1 teraton estimate for a 10 km rocky bolide impacting at 25 km/s

Taken from http://en.wikipedia.org/wiki/Richter_scale on 8/18/06

Earthquakes that are less than Earthquakes that are less than 2.52.5 are not are not usually felt by people.usually felt by people.

Approximately 20 major earthquakes in Approximately 20 major earthquakes in the magnitude 7.0-7.9 occur every the magnitude 7.0-7.9 occur every yearyear and each and each 5-105-10 years an earthquake of 8.0 years an earthquake of 8.0 or more will devastate a portion of Earth.or more will devastate a portion of Earth.

Location Date Magnitude1. Chile May 22, 1960 9.5

2. Prince William Sound, Alaska March 28, 19643 9.2

3. Andreanof Islands, Aleutian Islands March 9, 1957 9.1

4. Kamchatka Nov. 4, 1952 9.0

5. Off western coast of Sumatra, Indonesia Dec. 26, 2004 9.0

6. Off the coast of Ecuador Jan. 31, 1906 8.8

7. Rat Islands, Aleutian Islands Feb. 4, 1965 8.7

8. Northern Sumatra, Indonesia March 28, 2005 8.7

9. India-China border Aug. 15, 1950 8.6

10.

Kamchatka Feb. 3, 1923 8.5

Table taken from http://www.factmonster.com/ipka/A0763403.html on 8/18/06


Give examples of dangers to humans Give examples of dangers to humans from volcanic and earthquake from volcanic and earthquake activity.activity.

VI. Dangers to Humans from VI. Dangers to Humans from Earthquakes and VolcanoesEarthquakes and Volcanoes

Tell at least 4 of these hazards.Tell at least 4 of these hazards.

1)1) Fires (Ruptured gas or power lines)Fires (Ruptured gas or power lines)

2)2) Collapsing buildings/Falling DebrisCollapsing buildings/Falling Debris

3)3) Broken bridges and roadsBroken bridges and roads

4)4) Tsunamis (Seismic Sea Waves)Tsunamis (Seismic Sea Waves)

5)5) Lava flows melt and burnLava flows melt and burn

6)6) Volcanic ash & poisonous gases Volcanic ash & poisonous gases make it difficult to breathemake it difficult to breathe

Large submarine (under Large submarine (under waterwater) ) earthquakes or those that occur along earthquakes or those that occur along a coastline may result in tsunamis or a coastline may result in tsunamis or seismic sea waves.seismic sea waves.


Describe differences between p and s Describe differences between p and s wave transmission through the Earth wave transmission through the Earth and how it creates a shadow zone.and how it creates a shadow zone.

VII. Transmission of VII. Transmission of Earthquake WavesEarthquake Waves

The velocity of an The velocity of an earthquake wave earthquake wave varies according to varies according to densitydensity of the of the material through material through which it is traveling.which it is traveling.

The greater the The greater the density of the density of the material, the material, the greatergreater the velocity. the velocity.

Taken from http://www.earthscrust.org/earthscrust/science/historic/img/moho.gif on 8/18/06

As seismic waves travel As seismic waves travel through materials of through materials of different densities, the different densities, the velocityvelocity of the seismic of the seismic waves will change.waves will change.

This change in velocity This change in velocity of the wave causes the of the wave causes the wave to be bent or wave to be bent or refracted.refracted.

Since the density of the Since the density of the Earth gradually Earth gradually increasesincreases with depth, with depth, seismic waves tend to seismic waves tend to increaseincrease in their in their velocity and continually velocity and continually refract (bend)refract (bend) as they as they travel down into the travel down into the Earth.Earth.

Difference in P and S Wave Difference in P and S Wave TransmissionTransmission

Compressional or Compressional or p p waves are waves are transmitted transmitted through all phases through all phases of matter; of matter; solid, solid, liquid or gas.liquid or gas.

However, shear or However, shear or ss waves are only waves are only transmitted transmitted through through solidssolids..

This difference This difference provides valuable provides valuable information for information for scientists about the scientists about the compositioncomposition and and interior interior structurestructure of of the Earth.the Earth.

S waves that S waves that penetrate the penetrate the Earth Earth to the depth of the to the depth of the outerouter core core disappear.disappear.

Since these waves Since these waves are not transmitted are not transmitted by the outer core, by the outer core, the material of the the material of the outer coreouter core is is assumed to be assumed to be liquidliquid..

Taken from http://www.geo.cornell.edu/geology/classes/ Geo101/graphics/seismic_interior.jpgon 8/18/06

Earthquakes generate Earthquakes generate p p & & ss waves that move waves that move out from the out from the earthquake through earthquake through the Earth in all the Earth in all directions.directions.

Seismographs that are Seismographs that are located within located within 102102 degrees from the degrees from the epicenter record epicenter record both both p & s waves.p & s waves.

Those Those seismograph seismograph stations that are stations that are farther away than farther away than 102102oo do not record any do not record any ss waves because they waves because they are not transmitted are not transmitted through the through the core.core.

Taken from http://www.astronomynotes.com/solarsys/seismicb.gif on 8/18/06

A band that runs approximately 102A band that runs approximately 102oo to to 143143oo away away from the epicenter records from the epicenter records neitherneither p nor s waves. p nor s waves.

This is This is because p because p waves get waves get refractedrefracted out of out of that region.that region.This region is This region is called the called the shadow zoneshadow zone..


Describe a model of the Earth’s crust Describe a model of the Earth’s crust and interior. Be able to use ESRT and interior. Be able to use ESRT p.10 to describe characteristics of p.10 to describe characteristics of both the crust and interior.both the crust and interior.

C. Crust & Interior C. Crust & Interior PropertiesProperties

There are There are 44 major major Earth zones, three Earth zones, three solidsolid ones and one ones and one liquid.liquid.

The 3 solid zones The 3 solid zones are the are the crust, crust, mantle and inner mantle and inner corecore..

The only liquid zone The only liquid zone is the is the outer coreouter core..

See ESRT p.See ESRT p.1010

I. Crustal ThicknessI. Crustal Thickness The crust of the Earth compared to other The crust of the Earth compared to other

zones is relatively zones is relatively thinthin, only a few, only a few kilometerskilometers in average depth. in average depth.

The average thickness of the continental The average thickness of the continental crust is crust is greatergreater than the average thickness than the average thickness of the oceanic crust.of the oceanic crust.

Taken from http://www.deafhoosiers.com/sci/SOARHIGH/lithosphere/lithosphere.jpg on 8/18/06

II. Crustal CompositionII. Crustal Composition

The continental The continental crust is composed crust is composed mainly of felsic mainly of felsic igneous rock like igneous rock like granitegranite that is that is lowlow in in density.density.

The oceanic crust is The oceanic crust is composed mainly of composed mainly of mafic igneous rock mafic igneous rock like like basaltbasalt that is that is highhigh in density. in density.

Black sand beach of Hawaii

Taken from http://ruby.colorado.edu/~smyth/ Research/Images/Volcanix/Blacksand.jpg on 8/18/06

Granitic beach of Lake Ontario

Taken from http://www.dec.state.ny.us/website/ environmentdec/2006a/greatlakesagreement20106.jpg on 8/18/06

Interior StructureInterior Structure Crust sits on top of Crust sits on top of

mantle.mantle. Mantle accounts for the Mantle accounts for the

greatest part of the greatest part of the volume of the Earth.volume of the Earth.

The crust-mantle The crust-mantle boundary is called the boundary is called the Mohorovicic Mohorovicic Discontinuity or the Discontinuity or the Moho.Moho.

Below the mantle is the Below the mantle is the liquid liquid outerouter core and core and the solid the solid innerinner core. core.Taken from http://earthnet-geonet.ca/images/glossary/mantle.jpgon

8/18/06

Interior CompositionInterior Composition

Evidence from the behavior of Evidence from the behavior of seismic seismic waveswaves and metallic and metallic meteoritesmeteorites suggests suggests that the inner portion of the Earth is a high that the inner portion of the Earth is a high density combination of the metallic density combination of the metallic elements elements iron (Fe)iron (Fe) and and nickel (Ni).nickel (Ni).

Taken from http://buhlplanetarium3.tripod.com/CSC-Meteorite.JPG on 8/18/06

III. Characteristics of Earth’s InteriorIII. Characteristics of Earth’s Interior

The density, The density, temperature and temperature and pressure of the Earth’s pressure of the Earth’s interior interior increasesincreases with with depth. (ESRT p.depth. (ESRT p.1010). ). The density ranges The density ranges from from 2.7g/cm2.7g/cm33 for the for the continental crust and continental crust and 3.0g/cm3.0g/cm33 for the for the oceanic crust to oceanic crust to 12.7 12.7 g/cmg/cm33-13.0g/cm-13.0g/cm33 for for the inner core.the inner core.


Compare theories of continental drift Compare theories of continental drift and plate tectonics. Give evidence and plate tectonics. Give evidence that support the idea that continents that support the idea that continents have moved.have moved.

I. Plate Tectonics TheoryI. Plate Tectonics Theory Theory that Earth’s lithosphere is made of Theory that Earth’s lithosphere is made of

a number of solid plates that move in a number of solid plates that move in relation to each other.relation to each other.

ESRT p.5ESRT p.5

Continental DriftContinental Drift Theory that continents are now, as Theory that continents are now, as

well as in the past, shifting positions.well as in the past, shifting positions.

Although plate tectonics is a recent idea, it incorporates the earlier idea of Continental Drift put forth by Alfred Wegener in 1915.

Photo taken from http://www.uni-marburg.de/profil/Geschichte/wegner on 8/18/06

Wegener noted Wegener noted that the present that the present continentscontinents appear appear to fit together as to fit together as fragments of an fragments of an originally larger originally larger landmass, much landmass, much the same way the the same way the pieces of a pieces of a jigsaw jigsaw puzzlepuzzle fit together. fit together.

This is especially true if the edges of This is especially true if the edges of the the continental shelvescontinental shelves are used as are used as the boundaries.the boundaries.

However, over the years new evidence has been However, over the years new evidence has been collected that indicates that approximately collected that indicates that approximately 200 200 million years ago, the major continents were million years ago, the major continents were connectedconnected and since that time the continents have and since that time the continents have been moving generally been moving generally apart.apart.

The following diagrams show the Inferred Positions The following diagrams show the Inferred Positions of the Continents over the last 458 million years. of the Continents over the last 458 million years.

Label the Geologic Period for each diagram. Label the Geologic Period for each diagram. Diagrams found in ESRT on page Diagrams found in ESRT on page 99..

II. Evidence to Support Idea II. Evidence to Support Idea that Continents Have Movedthat Continents Have Moved

a)a) Many rock layers and Many rock layers and fossils can be fossils can be correlatedcorrelated across across ocean basins. Rock ocean basins. Rock types along with types along with mineral mineral compositioncomposition and the fossils found in and the fossils found in those rocks match up. those rocks match up.

A good example of this A good example of this are rocks and fossils are rocks and fossils found on the found on the easteast coast coast of South America of South America match those found match those found along the along the westwest coastline of Africa.coastline of Africa.

Diamonds found in Diamonds found in eastern Brazil are very eastern Brazil are very similar to those found similar to those found in western Africa.in western Africa.

More Evidence for Continental More Evidence for Continental MovementMovement

b)b) Some mountain Some mountain chains appear to chains appear to be be continuouscontinuous from continent to from continent to continent.continent.

Example: Example: Appalachians and Appalachians and CaledonianCaledonian


c)c) Rock and fossil evidence indicates ancient Rock and fossil evidence indicates ancient climates much climates much differentdifferent from those of from those of today.today.

Examples: Examples: glacial deposits in tropical glacial deposits in tropical regions or coal deposits in Arcticregions or coal deposits in Arctic


d)d) Rocks of the ocean basins are much Rocks of the ocean basins are much youngeryounger than continental rocks. than continental rocks.

The most conclusive evidence comes The most conclusive evidence comes from the ocean from the ocean basins.basins.


Explain evidence for sea floor Explain evidence for sea floor spreading from both spreading from both igneous ocean igneous ocean rocksrocks and the and the reversal of magnetic reversal of magnetic polaritypolarity..

III. Evidence to Suggest Sea III. Evidence to Suggest Sea Floor SpreadingFloor Spreading

There is much evidence to indicate that the There is much evidence to indicate that the ocean floors are ocean floors are spreadingspreading out from the mid- out from the mid-ocean ocean ridgesridges. The two major pieces of . The two major pieces of evidence are related to the age of evidence are related to the age of igneous igneous ocean materialsocean materials and the and the reversalreversal of of magneticmagnetic polarity.polarity.

Taken from http://www2.nature.nps.gov/geology/usgsnps/animate/A48.gif on 8/18/06

a) Igneous Ocean Rocksa) Igneous Ocean Rocks

The ocean crust is made up mainly of The ocean crust is made up mainly of basaltbasalt that is that is formed when formed when magmamagma (molten rock) rises, cools, (molten rock) rises, cools, solidifiessolidifies and and crystallizescrystallizes into igneous rocks of the into igneous rocks of the mid-ocean ridges.mid-ocean ridges.

Evidence shows that igneous rocks along the Evidence shows that igneous rocks along the center center of the of the mid-oceanmid-ocean ridge is ridge is youngeryounger (more (more recently formed) than the igneous rock found recently formed) than the igneous rock found fartherfarther from the mid-ocean ridge. from the mid-ocean ridge.

The age of igneous rock has been accurately The age of igneous rock has been accurately determined using determined using radioactiveradioactive dating techniques. dating techniques.

This suggests that as new This suggests that as new oceanocean crust is generated crust is generated at at mid-oceanmid-ocean ridges, the ocean floor widens. ridges, the ocean floor widens.

Taken from http://www.physicalgeography.net/fundamentals/images/seafloor_spreading.gif on 8/18/06

b) Reversal of Magnetic b) Reversal of Magnetic PolarityPolarity

The strips of The strips of basalticbasaltic rock that lie parallel to the mid- rock that lie parallel to the mid-ocean ocean ridgeridge show matched patterns of show matched patterns of magnetic magnetic reversals. reversals. Check out this animation!Check out this animation!

Over thousands of years, the magnetic poles of Earth Over thousands of years, the magnetic poles of Earth reversereverse their their polaritiespolarities. The magnetic north pole . The magnetic north pole changes to the magnetic changes to the magnetic southsouth pole and vice versa. pole and vice versa.

When the basaltic magma flows up in the middle of the When the basaltic magma flows up in the middle of the ridge and begins to ridge and begins to coolcool, crystals of magnetic , crystals of magnetic mineralsminerals align themselves with the Earth’s align themselves with the Earth’s magneticmagnetic field. This field. This alignment of minerals in the rock leaves a recording of alignment of minerals in the rock leaves a recording of magnetic magnetic polaritypolarity for the Earth at the time of rock for the Earth at the time of rock formation. formation.

When the Earth’s magnetic When the Earth’s magnetic fieldfield is reversed, the new is reversed, the new igneousigneous rocks formed during the reversed polarity period rocks formed during the reversed polarity period have their minerals aligned in an have their minerals aligned in an oppositeopposite direction from direction from the previously formed rocks. the previously formed rocks.

These changes in magnetic orientation are found in rock These changes in magnetic orientation are found in rock on both sides of the on both sides of the mid-oceanmid-ocean ridge, indicating that the ridge, indicating that the development of the ocean floor is form the development of the ocean floor is form the centercenter of the of the mid-ocean ridges outward.mid-ocean ridges outward.

Check out this animation!


Describe the 3 types of plate motion. Describe the 3 types of plate motion. Use ESRT p.5 to identify plate Use ESRT p.5 to identify plate boundaries.boundaries.

IV. Lithospheric Plates and IV. Lithospheric Plates and Plate BoundariesPlate Boundaries

Three kinds of plate motion are associated with plate Three kinds of plate motion are associated with plate boundaries; boundaries; convergent, divergent and transformconvergent, divergent and transform..

Taken from http://www.3villagecsd.k12.ny.us/Murphy/medina/eqs.html on 8/18/06

a) Convergent Plate a) Convergent Plate BoundariesBoundaries

Convergent Plate Boundaries- Convergent Plate Boundaries- plates plates collide with each othercollide with each other

Ocean Plate Meets Continental Ocean Plate Meets Continental PlatePlate1)1) If an oceanic plate collides If an oceanic plate collides

with a continental plate, the with a continental plate, the denser denser oceanocean plate made of plate made of basaltbasalt dives down dives down (subducts) into the mantle (subducts) into the mantle forming a forming a subduction zonesubduction zone with an ocean trench formed with an ocean trench formed at the surface.at the surface.

At the subduction zone, old At the subduction zone, old crust is consumed by the crust is consumed by the mantle to create more mantle to create more molten material. The molten material. The overriding overriding continentalcontinental plate plate made of made of granitegranite forms forms mountains. An example is mountains. An example is the the Andes of South America.Andes of South America.

Ocean Plate Meets Ocean Ocean Plate Meets Ocean PlatePlate

2)2) If two oceanic plates If two oceanic plates converge, the older, converge, the older, denserdenser plate will plate will subduct also forming a subduct also forming a trenchtrench on the surface on the surface along with a chain of along with a chain of islands called an islands called an island arcisland arc..

An example of this An example of this convergent subduction convergent subduction zone is the zone is the Northern Northern and Western and Western boundaries of the boundaries of the Pacific OceanPacific Ocean..

Continental Plate Meets Continental Continental Plate Meets Continental PlatePlate

3)3) If a continental If a continental plate collides with plate collides with another continental another continental plate, the edge of plate, the edge of both plates are both plates are crumpled up crumpled up forming forming folded folded mountainsmountains..

An example of this An example of this type of convergent type of convergent boundary is the boundary is the Himalayas of India.Himalayas of India.

Now look at the two diagrams of convergent boundaries in your note packet. Which one shows a subduction zone? Label the subduction zone in that diagram.

b) Divergent Plate b) Divergent Plate BoundariesBoundaries

Divergent Plate Divergent Plate Boundaries- Boundaries- plates plates move apartmove apart

A divergent boundary A divergent boundary allows allows heatheat and and magma magma to flow up to flow up from below forming from below forming parallel ridges made parallel ridges made of new crustal of new crustal material.material.

An example of a An example of a divergent plate divergent plate boundary like this is boundary like this is any any mid-ocean ridge.mid-ocean ridge.

In your note packet, label the parallel ridges formed from the upwelling magma in the divergent boundary diagram.

c) Transform Plate Boundaryc) Transform Plate Boundary Transform Plate Transform Plate

Boundary- Boundary- plates grind plates grind slowly past each otherslowly past each other

At this type of At this type of boundary, crust is boundary, crust is neither neither formedformed nor nor consumed.consumed.

An example is An example is San San Andreas Fault in Andreas Fault in California.California.

Shallow focus Shallow focus earthquakesearthquakes are very are very common at transform common at transform boundaries.boundaries.

In your note packet, label the shallow focus earthquakes in the transform diagram. Also place large arrows on each plate to show the direction of plate motion.

Taken from http://observe.arc.nasa.gov/nasa/ earth/tectonics/Tectonics3.html 0n 8/18/06

Plate Tectonic Map (ESRT p.Plate Tectonic Map (ESRT p.55))

Although plate motion is only a few Although plate motion is only a few centimeterscentimeters a year, a year, the interactions of the boundaries result in the interactions of the boundaries result in earthquakes, earthquakes, volcanoes volcanoes andand mountain building mountain building on a grand scale on a grand scale showing that the Earth is a showing that the Earth is a dynamicdynamic system. system.


Explain how mantle convection cells Explain how mantle convection cells are thought to be the method for are thought to be the method for moving crustal plates.moving crustal plates.

V. Mantle Convection CellsV. Mantle Convection Cells Although forces exist Although forces exist

within the Earth that within the Earth that are powerful enough to are powerful enough to move the lithospheric move the lithospheric plates, the scientific plates, the scientific community is not in community is not in total agreement on the total agreement on the specific mechanism specific mechanism (method) involved.(method) involved.

Convection cell- Convection cell- stream stream of heated material of heated material that is moving due to that is moving due to density differences density differences

Taken from http://www.sunblock99.org.uk/ sb99/people/KGalsgaa/convect.gif on 8/18/06

Taken from http://www.platetectonics.com/book/images/Convection.gif on 8/18/06Animation

Evidence suggests that convection cells exist Evidence suggests that convection cells exist within a part of the mantle called the within a part of the mantle called the asthenosphereasthenosphere because of the occurrence of heat because of the occurrence of heat flow highs in areas of flow highs in areas of mountain buildingmountain building and heat and heat flow lows in areas of flow lows in areas of shallow subsiding basins.shallow subsiding basins.

These convection cells may be part of the driving These convection cells may be part of the driving force which causes force which causes continentscontinents to move. to move.


What are hot spots? How are they What are hot spots? How are they formed?formed?

VI. Hot SpotsVI. Hot Spots Hot Spots- Hot Spots- places on Earth’s surface with places on Earth’s surface with

unusually high heat flowunusually high heat flow Most hot spots occur along Most hot spots occur along active plate active plate

marginsmargins but some are found within the but some are found within the plates.plates.

Hot spots are thought to be caused by Hot spots are thought to be caused by magma magma rising up from the mantle rising up from the mantle producing sites of active producing sites of active volcanism.volcanism.

As a plate passes over a hot spot, a chain of As a plate passes over a hot spot, a chain of volcanic mountain forms, like the volcanic mountain forms, like the Hawaiian Hawaiian Islands.Islands.The only mountain that remains an active The only mountain that remains an active volcano is the one located directly over the volcano is the one located directly over the hot hot spot.spot.

Wow! That was Dynamic!Wow! That was Dynamic!

Give me the test! I am ready!Give me the test! I am ready!

That’s All Folks!

Unit III Dynamic Crust Powerpoint

Technology

earths crust

dynamic crust

piece of crust

marine fossils

faulting movement of

position of rock layers

displaced deformed rock

animations http