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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?