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Geology of the Hawaiian IslandsGeology of the Hawaiian IslandsClass 31Class 31
44 May 2004May 2004
Exam ReviewExam Review EarthquakesEarthquakesand Tsunamisand Tsunamis
Deformation Deformation
Changes in volume or shape of a rock Changes in volume or shape of a rock bodybody= strain= strain
StressStress
The The forceforce that acts on a rock unit to that acts on a rock unit to change its shape and/or its volumechange its shape and/or its volumeCauses strain or deformationCauses strain or deformation
CompressionCompressionAction of coincident oppositely directed forces acting towards each other
TensionTensionAction of coincident oppositely directed forces acting away from each other
ShearShearAction of coincident oppositely directed forces acting parallel to each other across a surface in a couple
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Kinds of deformationKinds of deformation
Elastic Elastic vsvs Plastic Plastic Brittle Brittle vsvs DuctileDuctile
Factors that affect deformationFactors that affect deformation
TemperatureTemperature
PressurePressure
Strain rateStrain rate
Rock typeRock type
The variation of these factors determines if a rock will fault or fold.
Rocks are:Rocks are:
Elastic and brittle near the earth's Elastic and brittle near the earth's surfacesurfaceMore plastic and ductile deeper in the More plastic and ductile deeper in the crustcrustBecause of the increasing temperature Because of the increasing temperature and pressureand pressure
FoldsFolds
Most common ductile response to Most common ductile response to stress on rocks in the earth's cruststress on rocks in the earth's crust
FractureFracture
Most common brittle response to Most common brittle response to stress stress With With NoNo displacement = displacement = JointJointWith displacement = With displacement = FaultFault
Normal Fault Hanging walldrops down
Reverse FaultHanging wallmoves up
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Strike-slipFault EarthquakesEarthquakes
Focus = point where an earthquake originates
Epicenter = location at the surface directly above the focus
Most common types of Most common types of earthquake waves:earthquake waves:
PP--waveswaves and and SS--waveswavesPPrimaryrimary waves travel the fastest in the waves travel the fastest in the crust and usually are the first waves to crust and usually are the first waves to arrivearriveSSecondaryecondary (or S(or Shearhear) waves are ) waves are slower and therefore take longer to slower and therefore take longer to arrivearrive
P-waves are compressional Waves S-waves are Shear Waves
P-waves travel faster than S-waves,so they arrive at the recording station sooner
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Earthquake Magnitude Earthquake Magnitude Describes the strength of an Describes the strength of an earthquakeearthquakeMagnitude scale is exponential Magnitude scale is exponential ----magnitude 6 has 10 times greater magnitude 6 has 10 times greater amplitude of ground shaking than amplitude of ground shaking than magnitude 5magnitude 5
TsunamiTsunami
Series of very long-wavelength waves on the ocean
TsunamiTsunami
== "tidal wave" "tidal wave"
Tsunami has nothing to do Tsunami has nothing to do with tideswith tides
Tsunami waves Tsunami waves
Very small out in the open oceanVery small out in the open oceanAmplitude of only ~ 1 meterAmplitude of only ~ 1 meterVery long wavelengths (up to 100 km)Very long wavelengths (up to 100 km)Travel very fast (as much as 500 mph)Travel very fast (as much as 500 mph)
Tsunami waves Tsunami waves
When waves reach shallow water, they When waves reach shallow water, they "feel" the shallow bottom, just like "feel" the shallow bottom, just like ordinary waves, and they slow down (to ordinary waves, and they slow down (to 2020--30 mph)30 mph)Because of the massive energy, this Because of the massive energy, this slowdown causes them to build up very slowdown causes them to build up very high (up to 50high (up to 50--100 m)100 m)
Tsunami can be generated by any Tsunami can be generated by any process that displaces a large process that displaces a large amount of water: amount of water:
SubSub--sea earthquakessea earthquakesGiant landslides Giant landslides Volcanic eruptionsVolcanic eruptionsMeteorite impactsMeteorite impacts
RunupRunupMaximum height above sea level Maximum height above sea level reached by a tsunami when it reached by a tsunami when it reaches shorereaches shore
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Inundation Inundation Horizontal distance from the normal Horizontal distance from the normal water's edge reached by a tsunamiwater's edge reached by a tsunami
Hilo after 1946 tsunami
Coasts and BeachesCoasts and Beaches
Ocean water moves 3 ways: Ocean water moves 3 ways:
CurrentsCurrentsTides Tides WavesWaves
Currents Currents Water that is flowing from one part Water that is flowing from one part of the ocean to anotherof the ocean to another
Currents Currents Caused by: Caused by:
WindWindRotation of the earthRotation of the earthBreaking wavesBreaking wavesDensity differencesDensity differencesTidesTides
TidesTidesImportant because they change the Important because they change the area over which waves interact with area over which waves interact with the landthe landResult from the gravitational pull of the Result from the gravitational pull of the moon and the sun on the oceans moon and the sun on the oceans
Origin of Origin of the the
lunar lunar tidestides
The highest The highest and lowest and lowest tides occur tides occur due to the due to the
interaction of interaction of earth, moon, earth, moon,
and sunand sun
Fig. 14.68
Spring tides
Neap tides
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Tidal current Tidal current The horizontal flow of water that The horizontal flow of water that accompanies the rise and fall of the accompanies the rise and fall of the tidetideDuring times of rising tide, water flows During times of rising tide, water flows in toward the shore as a in toward the shore as a flood tideflood tidecurrentcurrentDuring times of falling tide, water flows During times of falling tide, water flows back out to sea as an back out to sea as an ebb tideebb tide currentcurrent
Waves Waves Very important erosive agentVery important erosive agentMany factors affect wavesMany factors affect wavesMost waves that hit Hawai`i are Most waves that hit Hawai`i are generated by winds in the open generated by winds in the open oceans hundreds of km awayoceans hundreds of km away
Wave Size determined by:Wave Size determined by:
Wind velocityWind velocityLength of time the wind blows Length of time the wind blows Distance over which the wind blows Distance over which the wind blows ((fetchfetch))
Wave Refraction Generation of Generation of longshorelongshore currentscurrents Wave erosionWave erosionMostly by Mostly by abrasionabrasionAlso by Also by hydraulic actionhydraulic action
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Fig. 14.18
Wave attack causes the land to be eroded back, leaving a wave-cut terrace
Beaches Beaches Temporary accumulations of rock fragmentsTemporary accumulations of rock fragmentsWave and current action separates the finer Wave and current action separates the finer debris (silt and clay) from the coarser debris (silt and clay) from the coarser fragments and deposits them in deeper water fragments and deposits them in deeper water offshoreoffshoreSand and boulders remain to form beachesSand and boulders remain to form beachesHawaiian beaches also have lots of shell Hawaiian beaches also have lots of shell fragmentsfragments
Problems Associated with Problems Associated with BeachesBeaches
People can cause many problems by People can cause many problems by trying to protect the shorelinetrying to protect the shoreline
Rise and fall of sea level and Rise and fall of sea level and its effect on Hawai`iits effect on Hawai`i
Sea Level ChangeSea Level ChangeSea level has fluctuated greatly over the Sea level has fluctuated greatly over the past 900,000 yearspast 900,000 yearsGlaciers hold large amounts of waterGlaciers hold large amounts of waterWhen they melt, the water goes into the When they melt, the water goes into the ocean and sea level risesocean and sea level risesWhen they expand, they pull water in from When they expand, they pull water in from the oceans and global sea level dropsthe oceans and global sea level drops
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Sea Level ChangeSea Level ChangeIn past 15,000 yrs, the glaciers have In past 15,000 yrs, the glaciers have been retreating and meltingbeen retreating and meltingGlobal sea level has risen to where it is Global sea level has risen to where it is todaytoday
Sea Level ChangeSea Level Change25% of Hawaii's natural, endemic 25% of Hawaii's natural, endemic vegetation grows along the coastal vegetation grows along the coastal zone zone Shorelines around the world, including Shorelines around the world, including those in Hawaii, are undergoing longthose in Hawaii, are undergoing long--term retreat due to rising sea levelterm retreat due to rising sea level
Hawaiian tide gages Hawaiian tide gages document a history document a history of local seaof local sea--level level
riserise
Sea Level is rising Sea Level is rising around the world at around the world at
1.5 to 2.2 1.5 to 2.2 cm/decadecm/decade
SLR is projected to SLR is projected to accelerate over the accelerate over the
next centurynext centurySeaSea--level rise forces shoreline retreat and erosionlevel rise forces shoreline retreat and erosion
Beach erosion vs. Coastal erosionBeach erosion vs. Coastal erosionCoastal erosion occurs when coastal area Coastal erosion occurs when coastal area moves inland due to rising sea levelsmoves inland due to rising sea levelsDuring coastal erosion the beaches move along During coastal erosion the beaches move along with the rest of the system and the beaches are with the rest of the system and the beaches are not erodednot eroded
Beach equilibriumBeach equilibriumEffect of Sea Level rise depends on slope of Effect of Sea Level rise depends on slope of beachbeach
Beach equilibriumBeach equilibriumBeaches respond to storms by Beaches respond to storms by retreating landward, either flattening retreating landward, either flattening their profile, or forming offshore barstheir profile, or forming offshore barsThe effect is to dissipate wave energy The effect is to dissipate wave energy over a broad zone and thus reduce over a broad zone and thus reduce shoreline retreatshoreline retreat
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Chronic coastal erosion is a statewide problemChronic coastal erosion is a statewide problem
Water quality suffers on armored shoresWater quality suffers on armored shoresHigh turbulence from wave reflectionHigh turbulence from wave reflection
Fleshy algal growthFleshy algal growthLittoral ecosystem heavily damaged Littoral ecosystem heavily damaged
Erosion is caused by Erosion is caused by 1. Sea1. Sea--level rise forcing shoreline retreat level rise forcing shoreline retreat 2. Waves and currents moving sand2. Waves and currents moving sand3. Human impacts to sand availability3. Human impacts to sand availability
Coral ReefsCoral ReefsConstructed from calcareous Constructed from calcareous
remains and secretions of remains and secretions of corals and calcareous algaecorals and calcareous algae
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Coral reefsCoral reefs
Grow best in waters with Grow best in waters with aveave. annual . annual temperature of 24temperature of 24°°C (75C (75°°F)F)Can’t survive sudden temp changes or Can’t survive sudden temp changes or prolonged exposure to temp less than prolonged exposure to temp less than 18 18 °°C C Require clear, sunlit waterRequire clear, sunlit waterLimiting depth of reef growth is about Limiting depth of reef growth is about 45 meters45 meters
Darwin’s AtollTheory
Drilling into Pacificatolls found basalt in the lagoons, confirm-ing the theory.
Many things can hurt reefsMany things can hurt reefs
WavesWavesStarfishStarfishCrownCrown--ofof--ThornsThornsPeoplePeople
GlaciersGlaciers
Why do we Why do we care?care?
They help They help control control global global climateclimate
GlacierGlacier
Body of ice, snow, Body of ice, snow, firnfirn, and , and meltwatermeltwaterlying wholly or mostly on land showing lying wholly or mostly on land showing evidence of present or former motionevidence of present or former motion
Glaciers form where more snow Glaciers form where more snow accumulates in winter than melts in accumulates in winter than melts in summer.summer.
Northern Northern hemisphere hemisphere
during during the last the last
glacial ageglacial age
Advances and retreats Advances and retreats of continental glaciersof continental glaciers
Worldwide and essentially Worldwide and essentially instantaneousinstantaneous
Implies Global climate controlImplies Global climate control
Glaciers and Sea Level ChangesGlaciers and Sea Level Changes
Lots of water in glaciers: during last ice Lots of water in glaciers: during last ice age sea level lowered by ~130 mage sea level lowered by ~130 m
If all ice in glaciers today would melt, sea If all ice in glaciers today would melt, sea level would rise 65m: Major parts of level would rise 65m: Major parts of Florida, Egypt, Hong Kong, London, Florida, Egypt, Hong Kong, London, Houston would be floodedHouston would be flooded
What causes ice ages?What causes ice ages?Variations in Earth's orbitVariations in Earth's orbit
Changes in the atmosphereChanges in the atmosphere
Changes in circulation of sea waterChanges in circulation of sea water
Changing position/relief of the continentsChanging position/relief of the continents
No single one of these explains all ice No single one of these explains all ice ages ages –– must be some combination.must be some combination.
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Thermohaline Oceanic Circulation
The climate system
Atmospheric COAtmospheric CO22 measured at Mauna Loameasured at Mauna Loa
CO2FossilFuels
Increases in COIncreases in CO22 and use of fossil fueland use of fossil fuel
Natural ResourcesNatural Resources
Two Kinds:Two Kinds:Renewable and NonRenewable and Non--renewablerenewable
Nonrenewable ResourcesNonrenewable ResourcesGeologic ResourcesGeologic ResourcesForm so slowly that they cannot be Form so slowly that they cannot be replenished in our lifetimesreplenished in our lifetimes
Geologic ResourcesGeologic Resources3 main categories:3 main categories:
Energy resources Energy resources –– petroleum (oil & petroleum (oil & natural gas), coal, uranium and natural gas), coal, uranium and geothermalgeothermalMetals Metals –– iron, copper, aluminum, gold, iron, copper, aluminum, gold, silver, platinum, etc.silver, platinum, etc.Nonmetallic: sand and gravel, Nonmetallic: sand and gravel, limestone (for cement), sulfur, gems, limestone (for cement), sulfur, gems, fertilizers, groundwaterfertilizers, groundwater
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World Petroleum Demand Currently very close to the level of supply
Petroleum in the U.S.Petroleum in the U.S.Domestic production (Sept., 2002) Domestic production (Sept., 2002)
= 8,870,000 BOPD*= 8,870,000 BOPD*Total use = 20,000,000 BOPDTotal use = 20,000,000 BOPDU.S. imports = 11,130,000 BOPDU.S. imports = 11,130,000 BOPDImports = 56%Imports = 56%
* Barrels of Oil Per Day* Barrels of Oil Per Day
U.S. Petroleum UseU.S. Petroleum Use
> 7 billion barrels of oil per year > 7 billion barrels of oil per year This is almost 30% of the earth’s oil use, This is almost 30% of the earth’s oil use, even though we only have 6% of the even though we only have 6% of the earth’s populationearth’s population
Alternatives to fossil fuelsAlternatives to fossil fuels
Nuclear energyNuclear energy
Solar EnergySolar Energy
Wind EnergyWind Energy
OTECOTEC
Geothermal EnergyGeothermal Energy
Sedimentary mineral depositsSedimentary mineral deposits
Banded iron formationsBanded iron formations
PlacersPlacers
ClaysClays
Sand and gravelSand and gravel
Chip Clark
ManganeseManganeseNoduleNodule
Geothermal ResourcesGeothermal Resources
Geo = earthGeo = earthThermal = heatThermal = heat
What is geothermal What is geothermal energy?energy?
Geothermal Geothermal energy is energy energy is energy derived from the derived from the earth's heatearth's heat
Old Faithful GeyserProblems with Geothermal EnergyProblems with Geothermal Energy
Geographically restrictedGeographically restrictedWhere would we expect to find Where would we expect to find Geothermal Resources?Geothermal Resources?
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Major elements Major elements of a Geothermal of a Geothermal Resource:Resource:
1. Heat source1. Heat source
2. Porous layer2. Porous layer
3. Fractures3. Fractures
4. Recharge4. Recharge
Geothermal Energy UseGeothermal Energy Use
High temperature water/steam High temperature water/steam used to generate electricityused to generate electricityLow temperature water used Low temperature water used directly for heatingdirectly for heating
U.S. use of Geothermal EnergyU.S. use of Geothermal EnergyU.S. is the world leader in geoU.S. is the world leader in geo--thermal energy thermal energy development with plant capacitydevelopment with plant capacity> 2,800 MW> 2,800 MW
BUT, only 4 states produce geothermal energy:BUT, only 4 states produce geothermal energy:Hawaii, California, Utah and NevadaHawaii, California, Utah and Nevada
Equivalent to 60 M barrels oil per yrEquivalent to 60 M barrels oil per yrOverall use of oil is > 7.3 Billion Overall use of oil is > 7.3 Billion b.ob.o./yr./yrGeothermal saves only 3 days’ oil use per yearGeothermal saves only 3 days’ oil use per yearGeothermal use < 1% of oil useGeothermal use < 1% of oil use
Advantages of Geothermal EnergyAdvantages of Geothermal Energy
Can be used instead of fossil fuels to Can be used instead of fossil fuels to produce electricityproduce electricityReplacing fossil fuels will reduce the Replacing fossil fuels will reduce the amount of air pollutants which can amount of air pollutants which can cause acid rain and contribute to cause acid rain and contribute to global warmingglobal warming
Advantages of Geothermal EnergyAdvantages of Geothermal Energy
Geothermal plant emits ~ 0.3 lb of Geothermal plant emits ~ 0.3 lb of carbon per carbon per MWhrMWhr electricity producedelectricity producedNatural gas electric plant emits ~ 280 lb Natural gas electric plant emits ~ 280 lb per per MWhrMWhrFuel oil plant emits ~420 lbs/Fuel oil plant emits ~420 lbs/MWhrMWhrCoal plant emits ~500 lbs/Coal plant emits ~500 lbs/MWhrMWhr
Advantages of Geothermal EnergyAdvantages of Geothermal Energy
It is very It is very reliablereliable
Advantages of Geothermal EnergyAdvantages of Geothermal Energy
Reducing the amount of oil shipped for Reducing the amount of oil shipped for electrical generation lessens the electrical generation lessens the possibility of oil spillspossibility of oil spillsGeothermal energy exists in large Geothermal energy exists in large amounts in Hawai`i, so shipping is not amounts in Hawai`i, so shipping is not necessarynecessary
Advantages of Geothermal EnergyAdvantages of Geothermal Energy
3030--megawatt geothermal power plant megawatt geothermal power plant on the Big Island displaces the need to on the Big Island displaces the need to burn about 500,000 barrels of fuel oil burn about 500,000 barrels of fuel oil every yearevery yearEliminates > 220,000 tons of COEliminates > 220,000 tons of CO22 that that an oilan oil--fired plant would have emittedfired plant would have emitted
Disadvantages of Geothermal EnergyDisadvantages of Geothermal Energy
Geothermal fluids are corrosive Geothermal fluids are corrosive ---- they they eat away at pipes and equipment, so eat away at pipes and equipment, so maintenance costs are highmaintenance costs are highFluids can get into groundwater and Fluids can get into groundwater and contaminate it contaminate it ---- need to be careful need to be careful with waste waterwith waste water
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Disadvantages of Geothermal EnergyDisadvantages of Geothermal Energy
Steam contains toxic gasesSteam contains toxic gasesHydrogen sulfide is the worstHydrogen sulfide is the worst
Disadvantages of Geothermal EnergyDisadvantages of Geothermal Energy
Some residents may not want Some residents may not want geothermal activities to occur in geothermal activities to occur in certain areas (such as rain forests)certain areas (such as rain forests)Some native Hawaiians oppose the Some native Hawaiians oppose the development of geothermal power development of geothermal power because it interferes with their worship because it interferes with their worship of of PelePele
Disadvantages of Geothermal EnergyDisadvantages of Geothermal Energy
Geothermal wells are sometimes Geothermal wells are sometimes vented for a few hours to clear the well vented for a few hours to clear the well and pipe lines resulting in a temporary and pipe lines resulting in a temporary release of steam and other gasesrelease of steam and other gasesSuch events can be noisy Such events can be noisy Some continuous lowSome continuous low--level noise is level noise is also generated during normal power also generated during normal power plant operationsplant operations
Local Environmental IssuesLocal Environmental IssuesDegradation of the EnvironmentDegradation of the EnvironmentSewage Discharge into Coastal AreasSewage Discharge into Coastal AreasRunoff into the Coastal AreasRunoff into the Coastal Areas
Sewage Discharge into Coastal AreasSewage Discharge into Coastal Areas
Impacts to the reefs from sewage Impacts to the reefs from sewage discharges have ceaseddischarges have ceasedFormerly damaged areas are Formerly damaged areas are recoveringrecovering
Secondary Treatment Necessary?Secondary Treatment Necessary?
Local environmental groups are Local environmental groups are pressing the City of Honolulu to pressing the City of Honolulu to convert all of their facilities to convert all of their facilities to secondary treatment levelssecondary treatment levelsDo we need to subject sewage to Do we need to subject sewage to secondary treatment before dumping it secondary treatment before dumping it in the ocean?in the ocean?
Secondary Treatment Necessary?Secondary Treatment Necessary?
The absence of oxygen depletion The absence of oxygen depletion problem in Hawaiian coastal waters is problem in Hawaiian coastal waters is main reason that the EPA has allowed main reason that the EPA has allowed the City of Honolulu to operate its two the City of Honolulu to operate its two largest plants as primary, rather than largest plants as primary, rather than secondary, treatment facilitiessecondary, treatment facilities
Secondary Treatment Secondary Treatment NeccearyNecceary??Hawai`i is unlike many parts of the Hawai`i is unlike many parts of the mainland, because there is not a broad, mainland, because there is not a broad, shallow continental shelfshallow continental shelfBecause of the steep marine slopes off Because of the steep marine slopes off the islands, sewage dumped at 100 ft the islands, sewage dumped at 100 ft depth moves offshore and is diluted in depth moves offshore and is diluted in the channels between the islandsthe channels between the islands
Local Environmental and Geology Local Environmental and Geology Issues in the NewsIssues in the News
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Energy TopicsEnergy Topics Runoff into Runoff into nearshorenearshore areasareas
Beach ErosionBeach Erosion
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LandslidesLandslides
Questions? Questions?