lecture 15 cold climates glaciers and ice ages glacier: a large, long-lasting mass of ice, formed on...
TRANSCRIPT
![Page 1: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/1.jpg)
Lecture 15 Cold ClimatesLecture 15 Cold ClimatesGlaciers and Ice AgesGlaciers and Ice Ages
• Glacier: a large, long-lasting mass of ice, Glacier: a large, long-lasting mass of ice, formed on land that moves under the formed on land that moves under the influence of gravityinfluence of gravity
• Glaciers form by accumulation and Glaciers form by accumulation and compaction of snowcompaction of snow– Packed snow becomes Packed snow becomes firnfirn
– Then refreezes to iceThen refreezes to ice
Davidson Glacier near Haines, AlaskaDavidson Glacier near Haines, Alaska
http://www.aad.gov.au/asset/webcams/mawson/
![Page 2: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/2.jpg)
Formation of Glacial Ice from SnowFormation of Glacial Ice from Snow
snowball
iceball
Alpine Glacier: it is just a frozen river
![Page 3: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/3.jpg)
Types of GlaciersTypes of Glaciers
Alpine
Continental
Alpine glaciation: found in mountainous regions Alpine glaciation: found in mountainous regions Continental glaciation: exists where a large part of a continent is covered by glacial iceContinental glaciation: exists where a large part of a continent is covered by glacial ice
Cover vast areas
![Page 4: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/4.jpg)
Alpine GlaciersAlpine Glaciers– Cirque Glacier– Cirque Glacier
Mount Edith Cavell, Jasper National Park, Canada
![Page 5: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/5.jpg)
Alpine Glaciers Alpine Glaciers – Valley Glacier– Valley Glacier
Tongas National Forest, Alaska
Lateral and medial moraines
![Page 6: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/6.jpg)
Types of Glaciers Types of Glaciers – Icecap and Continental– Icecap and Continental
Sentinal Range, Antarctica
http://www.nmm.ac.uk/server/show/conWebDoc.1221
•Antarctica is the broadest high place on Earth, the ice cap is up to 4km thick and covers the continent•Antarctica is a desert, with only 15 cm (6 inches) of snowfall a year around the South Pole. The air is too cold to hold much moisture.•The lowest recorded temperature is -89.2 °C.•There is no life in Antarctica except near the coast
![Page 7: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/7.jpg)
http://www.aad.gov.au/asset/webcams/mawson/
![Page 8: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/8.jpg)
Types of Glaciers Types of Glaciers – Piedmont & Tidewater– Piedmont & Tidewater
Source: Jim Wark/Peter Arnold, Inc.
Piedmont: Originally confined alpine, spread at foot of mountains
Calving
![Page 9: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/9.jpg)
Iceberg Calving Iceberg Calving – – Hubbard Glacier, Wrangell-St. Elias National Park, AlaskaHubbard Glacier, Wrangell-St. Elias National Park, Alaska
![Page 10: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/10.jpg)
A Glacier’s BudgetA Glacier’s Budget
• Budget = Gain – Loss
• Gains snow in zone of accumulation
• Loses ice in zone of ablation
• Budget can be positive (net growth)
• Static
• or negative (net melting)
![Page 11: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/11.jpg)
A Glacier’s BudgetA Glacier’s Budget
Summer Rain
Year round Snow
Note that a glacier is a river. Even if the terminus doesn’t advance, it still flows downhill
![Page 12: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/12.jpg)
Mechanics of Glacial FlowMechanics of Glacial FlowInternal deformationInternal deformation
Ice crystals slide past one anotherIce crystals slide past one anotherBasal Sliding Basal Sliding Entire glacier slides downhill on a thin film of Entire glacier slides downhill on a thin film of meltwater at its base.meltwater at its base.Glacier always flows toward zone of ablationGlacier always flows toward zone of ablation
Basal Sliding Discussion:Ice skates and sleds
![Page 13: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/13.jpg)
Erosion 1: Glacial Abrasion in BedrockErosion 1: Glacial Abrasion in Bedrock
Source: Tom Bean
Glaciers cause erosion
Rock embedded in Ice
![Page 14: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/14.jpg)
Glacial Erosion – Roche MoutonéeGlacial Erosion – Roche Moutonée
FROST WEDGING
2. Quarrying
![Page 15: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/15.jpg)
Glacial Erosion – Roche MoutonéeGlacial Erosion – Roche Moutonée
Yosemite NP, Calif
![Page 16: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/16.jpg)
Erosion by Glaciers (cont.)Erosion by Glaciers (cont.)• Alpine glaciers erode mountain slopes Alpine glaciers erode mountain slopes
into horseshoe shaped basins called into horseshoe shaped basins called cirquescirques– Melting forms cirque lake (Melting forms cirque lake (tarntarn))
• Erosion of two or more cirques erodes Erosion of two or more cirques erodes intervening rockintervening rock– Horns :pointy peaks made by triosHorns :pointy peaks made by trios
– Arêtes: long serrated ridges by pairsArêtes: long serrated ridges by pairs
– Cols: passes through the arêtesCols: passes through the arêtes
![Page 17: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/17.jpg)
Alpine Glacial ErosionAlpine Glacial Erosion
Cirque and valley glaciers form in river valleys, cut U-shapes
![Page 18: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/18.jpg)
Alpine Glacial ErosionAlpine Glacial Erosion
Cirque glaciers erode uphill, widenValley glaciers enlarge
Arêtes, Horn, Col, HANGING VALLEYS
![Page 19: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/19.jpg)
Yosemite Falls from Hanging ValleyYosemite Falls from Hanging Valley
![Page 20: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/20.jpg)
U-ShapedU-Shaped Glacial Glacial Valley in Southeastern AlaskaValley in Southeastern Alaska
Valley glaciers erode a large quantity of bedrock and sedimentValley glaciers erode a large quantity of bedrock and sediment
Convert V-shaped stream valleys into U-shaped glacial valleysConvert V-shaped stream valleys into U-shaped glacial valleys..
![Page 21: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/21.jpg)
Seawater Flooded U-ShapedSeawater Flooded U-Shaped Valleys: FjordsValleys: FjordsBela Bela Fjord, BC
Sea Level rose as glaciers melted
![Page 22: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/22.jpg)
Erosion by Continental GlaciationErosion by Continental Glaciation
• Erosional Landforms much larger in scale than alpine glaciers
–Whalebacks – huge Roche Moutonée
–Huge U-shaped troughs
– Finger Lakes, Great Lakes, Puget Sound, Loch Ness were all once stream valleys excavated by Ice Sheets
![Page 23: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/23.jpg)
Erosion by Continental Glaciation (Great Lakes, Finger Lakes)Erosion by Continental Glaciation (Great Lakes, Finger Lakes)
Source: U.S. Dept. of Interior, USGS Eros Date Center
Superior
Michigan
Huron
Erie
Ontario
![Page 24: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/24.jpg)
Glacial Deposits - DriftGlacial Deposits - Drift
• Collectively called Glacial Drift• TYPE 1: UNSORTED• Glacial Till: unsorted, unstratified
sediments deposited by melting ice.– May contain glacial erratics– Often accumulates at glacier’s terminus as a
Terminal Moraine: hills of sediment left by a glacier’s retreat.
– Moraines may be reshaped by a later glacial advance into Drumlins: rounded elongated hills
![Page 25: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/25.jpg)
Advance & Retreat: MorainesAdvance & Retreat: Moraines
Note moraine, no matter direction
Analogy: Escalator
![Page 26: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/26.jpg)
Discussion: Advance & Retreat of Discussion: Advance & Retreat of Glaciers and Terminal MorainesGlaciers and Terminal Moraines
![Page 27: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/27.jpg)
Large Granite Erratics Large Granite Erratics Favored by climbers with families
![Page 28: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/28.jpg)
Medial MorainesMedial Moraines
![Page 29: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/29.jpg)
Medial Moraines Medial Moraines – – Kennicott GlacierKennicott Glacier
Wrangell-St. Elias NP, SE AK
![Page 30: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/30.jpg)
The Origin of DrumlinsThe Origin of Drumlins
Glacier retreats, leaving a terminal moraine. Then it advances again, and redistributes the drift as a spoon shaped hill called a drumlin.
![Page 31: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/31.jpg)
Drumlins Drumlins Rochester,NYRochester,NY
![Page 32: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/32.jpg)
Glacial Deposits - DriftGlacial Deposits - Drift
• TYPE 2: SORTED
• Outwash: sorted stratified sediments deposited by meltwater streams
• Loess: wind erosion of drying outwash silt.
• Eskers: sinuous meltwater deposits of sand and gravel underneath ice
![Page 33: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/33.jpg)
Origin of EskersOrigin of Eskers
![Page 34: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/34.jpg)
Eskers and Kettles in South DakotaEskers and Kettles in South Dakota
![Page 35: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/35.jpg)
Effects of GlaciationEffects of Glaciation
• Change Climate – increase precipitation
pluvial lakes
• Depress continents & lateral rebound
• Drop sea-level: alter coastlines
• Moraines form Dams – Proglacial Lakes– Divert streams – Ohio and Missouri rivers
![Page 36: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/36.jpg)
Formation of Terraces due to Crustal ReboundFormation of Terraces due to Crustal Rebound
![Page 37: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/37.jpg)
Lowered Sea-level - Land bridgeLowered Sea-level - Land bridge
BeringGlacier grows, sea-level drops
![Page 38: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/38.jpg)
Lowered Sea-level exposed continental shelfLowered Sea-level exposed continental shelf
Massive extinctions of shallow-water
marine organisms
![Page 39: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/39.jpg)
The Creation of Glacial Lake MissoulaThe Creation of Glacial Lake Missoula
Purcell Lobe blocks Clark Fork River
![Page 40: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/40.jpg)
The Draining of Glacial Lake Missoula The Draining of Glacial Lake Missoula
Repeated many times, last time 13000 kya
![Page 41: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/41.jpg)
Giant Ripples of the Missoula FloodingGiant Ripples of the Missoula Flooding
Giant Ripples
Country road for scale
Flood kills everything in its path, 26 times
![Page 42: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/42.jpg)
Max Glacier Distribution 20,000 yaMax Glacier Distribution 20,000 ya
Maximum glaciation occurs at coincidence of three astronomical cycles
if high land in polar latitudes
![Page 43: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/43.jpg)
Causes of Ice AgesCauses of Ice Ages• Plate Tectonics
Moves Continents to Poles
Raises mountains above snowline
Albedo increases, colder, spread
• Orbit distance, Axis Tilt and Wobble– Moderates solar radiation past 65o Latitude– Croll-Milankovitch Cycles ~ every 100,000 years– With many smaller cycles between– Need low summertime radiation past 65o Latitude
less melting, glaciers expand
![Page 44: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/44.jpg)
Milankovitch Cycles Milankovitch Cycles
100,000 years
The energy of solar radiation drops off as the square of the distanceFurther awayNot as hot
http://en.wikipedia.org/wiki/Milankovitch_cycles
![Page 45: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/45.jpg)
41,000 years
Cold Dry Winter Hot SummerSnow meltsGlaciers shrink
Warm Wet Winter Cool SummerSnow doesn’t meltGlaciers grow
High latitude getting more sunlight in summer
High latitude getting less sunlight in summer
High latitude getting more sunlight in winter
![Page 46: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/46.jpg)
![Page 47: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/47.jpg)
25,700 years
at Perihelion
at Perihelion
Determines which hemisphere gets conditions suitable for glaciation
![Page 48: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/48.jpg)
One More Point On ThisOne More Point On This
• The orbital affects that Milankovitch suggested as a partial cause for ice ages each have a different period.
• They combine at irregular intervals
• Many glaciation peaks are about 100,000 years apart, but that is ONLY an average. This suggests that orbital ellipticity is important. The worst glaciations occur when minimum tilt coincides with maximum ellipticity.
![Page 49: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/49.jpg)
Earth’s Past Ice AgesEarth’s Past Ice Ages
• Tertiary to Quaternary cooling – Pleistocene• None in Mesozoic• Late Pennsylvanian & Permian in southern continents (Gondwana)• Ordovician glaciation (Gondwana)
– Area that is now the Sahara at South Pole• PreCambrian Tillites (Lithified Till)
– Three, maybe four,episodes– Oldest 2.8 bya – 750 mya ice from poles to tropic “Snowball Earth”
Cenozoic
Mesozoic
Paleozoic
Paleozoic
PreCambrian
![Page 50: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/50.jpg)
Permian Glaciation – Gondwana TillitesPermian Glaciation – Gondwana Tillites
![Page 51: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/51.jpg)
Cenozoic CoolingCenozoic CoolingCentral America Forms
Southern Ocean forms
![Page 52: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/52.jpg)
Foraminifera tests - Ice AgeForaminifera tests - Ice Age
1. Evap. water and CO2
removes 16O from oceans18O left in oceans used to make shells
3. Also spiral direction & diversity depends on Temp.
Nebraskan
Kansan
Illinoian
Wisconsinan
About 30 pulses in 4 or so major
groups
ColdWarm
2. Ice traps CO2 and water with light
oxygen
![Page 53: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/53.jpg)
Continuous Ice Sheet 20 kyaContinuous Ice Sheet 20 kya
Scoured 30 M below sea-level
![Page 54: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/54.jpg)
Global Temperatures Cycle, largest Global Temperatures Cycle, largest 100,000 Year (orbit eccentricity)100,000 Year (orbit eccentricity)
Smaller signals about 25K and 41KInterglacials get really WARM
![Page 55: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/55.jpg)
The HoloceneThe Holocene
• Latest retreat began 10,000 years agoLatest retreat began 10,000 years ago• Climate varied. Hot Climate varied. Hot 8000 – 4000 ya8000 – 4000 ya
• Medievil Warm: 800 – 1200 ADMedievil Warm: 800 – 1200 AD
• Little ice age 1200 AD until 1850Little ice age 1200 AD until 1850
• Widespread Famine Widespread Famine
• 1253 Pueblo cliff-dwellings abandoned.1253 Pueblo cliff-dwellings abandoned.
• 1340s AD Black Death Bubonic Plague1340s AD Black Death Bubonic Plague
http://en.wikipedia.org/wiki/Little_Ice_Age
![Page 56: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/56.jpg)
Thousands of Years BP
Mann’s Hockey Stick
http://en.wikipedia.org/wiki/Image:Holocene_Temperature_Variations.png
2004 oC
Holocene Temperature Variations
-1
+1
12 6 0
Waterfreezes
![Page 57: Lecture 15 Cold Climates Glaciers and Ice Ages Glacier: a large, long-lasting mass of ice, formed on land that moves under the influence of gravityGlacier:](https://reader035.vdocuments.site/reader035/viewer/2022062321/56649dbf5503460f94ab3c7c/html5/thumbnails/57.jpg)
Sustained warming since 1850Sustained warming since 1850Athabaska Glacier, Columbia Icefield,
W. Canada2005 Greenland glacier
retreated 9 miles!
Antarctic Glaciers started melting this season