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Geology of the Hawaiian IslandsGeology of the Hawaiian IslandsClass 25Class 25

13 April 200413 April 2004

Any Questions?Any Questions? Earth Systems Today CDEarth Systems Today CDClick on “Weather and Climate”Click on “Weather and Climate”Look at the sections onLook at the sections on

El NiEl NiññooOzone HoleOzone Hole

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.

Types of GlaciersTypes of Glaciers

alpine:alpine: restricted to mountainous systemsrestricted to mountainous systems

continentalcontinental: covers extremely large areas: covers extremely large areas

Antarctica: 12,500,000 kmAntarctica: 12,500,000 km22 up to 3 km up to 3 km thick, 80% of the ice on earth, 65% of thick, 80% of the ice on earth, 65% of the fresh waterthe fresh water

Greenland: 1,700,000 kmGreenland: 1,700,000 km22 3.2 km thick3.2 km thick

Sentinel Range, AntarcticaMorphological classificationMorphological classification

Valley glacier Valley glacier

Ice cap glacierIce cap glacier

Ice sheet glacierIce sheet glacier

Greenland Greenland Ice CapIce Cap

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Antarctic Antarctic Ice SheetIce Sheet

Glacial BudgetGlacial Budget(Net Loss)

Calving Glacier,Glacier

Bay,Alaska

Stages of Antarctic Stages of Antarctic Ice Shelf RetreatIce Shelf Retreat

Ice Flow in a Ice Flow in a Continental Continental

GlacierGlacier

Glacial erosionGlacial erosionVV--shaped valley shaped valley vs.vs. UU--shapedshaped

hanging valleyshanging valleys

Creation of Creation of Hanging Hanging

Valleys and Valleys and Associated Associated Waterfalls, Waterfalls, Before and Before and

After After GlaciationGlaciation

U-shaped Glacial Valley, Glacier National Park,

Montana

Steve Kaufman/DRK

Glacial Polish, Striations, and

Grooves, Glacier Bay National

Park,Alaska

Carr Clifton

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Stephen J. Krasemann/DRK Photo

LateralMoraines

MedialMoraines

Pleistocene continental Pleistocene continental glaciationglaciationGreat ice sheets extended into temperateGreat ice sheets extended into temperateregions 4 times in the past:regions 4 times in the past:

WisconsinWisconsin 0.20 0.20 –– 0.018 Ma0.018 Ma

IllinoianIllinoian 0.55 0.55 –– 0.40 Ma0.40 Ma

KansanKansan 1.40 1.40 –– 0.95 Ma0.95 Ma

NebraskanNebraskan 2.00 2.00 –– 1.75 Ma1.75 Ma

Northern Northern hemisphere hemisphere

during during the last the last

glacial ageglacial age

Ice cores from the Vostok Station,

Antarctica

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

Oxygen isotopes and the record Oxygen isotopes and the record of global climate changeof global climate change

Ordinary Oxygen has atomic mass of Ordinary Oxygen has atomic mass of 16 (O16 (O--16)16)

OxygenOxygen--18 has 2 extra neutrons, so its 18 has 2 extra neutrons, so its atomic mass is 18 (Oatomic mass is 18 (O--18)18)

Oxygen isotopes and the record Oxygen isotopes and the record of global climate changeof global climate change

During glacial times, ODuring glacial times, O--16 is 16 is preferentially evaporated from the preferentially evaporated from the oceans because it is lighteroceans because it is lighter

OO--16 is then precipitated and 16 is then precipitated and “captured” by glaciers, leaving the “captured” by glaciers, leaving the oceans with a higher concentration of oceans with a higher concentration of OO--1818

Oxygen isotopes and the record Oxygen isotopes and the record of global climate changeof global climate change

Foraminifera are small animals in the Foraminifera are small animals in the oceans that secrete calcium carbonate oceans that secrete calcium carbonate shellsshells

During glacial times, the oxygen in their During glacial times, the oxygen in their shells is higher in Oshells is higher in O--18 than O18 than O--16 16

Isotopic record of changing ice volume over the Isotopic record of changing ice volume over the past 2 million years based on deeppast 2 million years based on deep--sea coressea cores

Fig. 12.32

Millions of Years Before Present

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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. Geometry of Earth’s

orbital variations and tilt

Global wind Global wind patternspatterns

Thermohaline Oceanic Circulation

Global Circulation Patterns Established

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Circulation is cut off High Mountains Change Atmospheric Circulation Patterns

The Hydrologic The Hydrologic CycleCycle

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Ozone is a molecule formed of 3 Oxygen atoms (O3) that forms a natural filter, absorbing the harmful rays of the sun.

Chlorofluorocarbons in the atmosphere are attacked by UV radiation

Chlorofluorocarbons in the atmosphere are attacked by UV radiation, liberating a chlorine atom

Chlorine combines with O atoms

Chlorine combines with O atoms to form ClO

ClO atoms then attack Ozone

ClO atoms then attack Ozone to liberate O2 into the atmosphere

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2 Ozone atoms are thus changed into 3 O2 atoms

The Problem:

O2 is transparent to harmful UV rays, so they pass through

Effect of greenhouse gases on incoming and outgoing radiation

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

Historical Historical temperature temperature

changeschanges

Predicted increases in winter temperatures Predicted increases in winter temperatures with doubling of COwith doubling of CO22

Questions? Questions?

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ThursdayThursday

Last Web Class Last Web Class –– Kaua`iKaua`i and the NW and the NW Hawaiian IslandsHawaiian Islands

Don’t forget to do the last Virtual Field Don’t forget to do the last Virtual Field Trip and onTrip and on--line quizline quiz