Glaciers and Periglacial Landforms Processes and Landforms Paleoclimatology
Overview <ul><li>Glaciers </li></ul><ul><li>Glacial Processes </li></ul><ul><li>Glacial Landforms Periglacial Landscapes <...
Objectives <ul><li>Describe the different forms of glaciers in terms of the similarity of their formation and differences ...
Glaciers <ul><li>Definition:  A large mass of ice, flowing across the land under the influence of gravity and their own we...
 
 
<ul><ul><li>Continental glaciers:  continuous expanses of solid ice that subsume broad landscapes, including drainage syst...
 
 
 
Glacial Processes <ul><li>Formation </li></ul><ul><ul><li>Zone of Accumulation:  area above snowline where snow exists yea...
 
<ul><li>Mass Balance </li></ul><ul><ul><li>Above the snow line, in the Zone of Accumulation, mass is added to the glacier ...
 
 
 
<ul><li>Glacial Movement </li></ul><ul><ul><li>Simultaneous sliding and oozing motion </li></ul></ul><ul><ul><li>Frictiona...
 
 
Glacial Landforms <ul><li>Erosion </li></ul><ul><ul><li>Plucking </li></ul></ul><ul><ul><li>Abrasion </li></ul></ul><ul><l...
 
 
 
 
 
<ul><li>Erosional Features of Alpine Glaciers </li></ul><ul><ul><li>Modified upslope drainage </li></ul></ul><ul><ul><ul><...
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
<ul><li>Depositional Features of Alpine Glaciers </li></ul><ul><ul><li>Glacial Drift </li></ul></ul><ul><ul><ul><li>Deposi...
 
 
 
<ul><li>Features of Continental Glaciation </li></ul><ul><ul><li>Erosional features </li></ul></ul><ul><ul><ul><li>derange...
 
 
 
 
 
 
 
 
Periglacial Landscapes <ul><li>Features of Subarctic and Polar (tundra) climates that are not directly related to glaciati...
<ul><li>Permafrost </li></ul><ul><ul><li>develops after soil and rock have been below freezing for at least 2 consecutive ...
 
 
<ul><ul><li>Permafrost behavior </li></ul></ul><ul><ul><ul><li>Active layer:  exposed to daily and seasonal freezes and th...
<ul><li>Ground Ice and Frozen Ground </li></ul><ul><ul><li>Refers to frozen subsurface water </li></ul></ul><ul><ul><ul><l...
<ul><ul><li>Landforms </li></ul></ul><ul><ul><ul><li>Pingos:  frozen injected artesian water, forming a circular mound, so...
 
 
 
 
 
 
The Pleistocene <ul><li>1.8 million to 10,000 years ago </li></ul><ul><ul><li>Ice sheets and glaciers covered 1/3 of Earth...
 
 
 
 
<ul><li>Features </li></ul><ul><ul><li>Formation of the Great Lakes </li></ul></ul><ul><ul><ul><li>Drainage systems enlarg...
 
 
Paleoclimatology <ul><li>The study of past climates and their change over time </li></ul><ul><ul><li>Ice cores </li></ul><...
 
<ul><li>Mechanisms of Climate Change </li></ul><ul><ul><li>Variations in Earth-Sun relations </li></ul></ul><ul><ul><ul><l...
 
 
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Glaciers

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Transcript of "Glaciers"

  1. 1. Glaciers and Periglacial Landforms Processes and Landforms Paleoclimatology
  2. 2. Overview <ul><li>Glaciers </li></ul><ul><li>Glacial Processes </li></ul><ul><li>Glacial Landforms Periglacial Landscapes </li></ul><ul><li>The Pleistocene </li></ul><ul><li>Paleoclimatology </li></ul>
  3. 3. Objectives <ul><li>Describe the different forms of glaciers in terms of the similarity of their formation and differences in spatial extent </li></ul><ul><li>Explain the interrelationships between the processes of glacier formation, and those of glacial motion </li></ul><ul><li>Relate glacial motion to the geomorphological themes of erosion, transportation and deposition, and describe the landforms associated with each </li></ul><ul><li>Identify various glacial landforms and describe the processes that created them </li></ul><ul><li>Describe the features and processes of periglacial landscapes </li></ul><ul><li>Describe some of the significant features of the Pleistocene </li></ul><ul><li>Identify major sources of climatic variability and explain how they contribute to climate change </li></ul>
  4. 4. Glaciers <ul><li>Definition: A large mass of ice, flowing across the land under the influence of gravity and their own weight </li></ul><ul><li>Types </li></ul><ul><ul><li>Alpine glaciers: Mountain glaciers, follow drainage patterns </li></ul></ul><ul><ul><ul><li>Snowfield: area above snowline which provides ice for glaciers </li></ul></ul></ul><ul><ul><ul><li>Cirque glaciers: glaciers originating in basins of accumulated snow </li></ul></ul></ul><ul><ul><ul><li>Valley glaciers: several cirque glaciers merge into a greater downstream flow </li></ul></ul></ul><ul><ul><ul><li>Piedmont glaciers: after leaving the mountain slopes, several valley glaciers can merge into a larger flow across the landscape </li></ul></ul></ul><ul><ul><ul><li>Tidal glaciers: occur if a glacier reaches the sea. Large pieces of ice can break off forming ice bergs </li></ul></ul></ul>
  5. 7. <ul><ul><li>Continental glaciers: continuous expanses of solid ice that subsume broad landscapes, including drainage systems and surrounding peaks </li></ul></ul><ul><ul><ul><li>Ice sheets </li></ul></ul></ul><ul><ul><ul><ul><li>cover entire continental masses </li></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Antarctica (90% coverage) </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Greenland (81% coverage) </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><li>ice mass can achieve depths of 2000 – 3000 meters </li></ul></ul></ul></ul><ul><ul><ul><ul><li>actual landmasses can be isostatically depressed below sea level </li></ul></ul></ul></ul><ul><ul><ul><li>Ice caps </li></ul></ul></ul><ul><ul><ul><ul><li>covers an area less than 50,000 sq. km. and typically has a circular shape </li></ul></ul></ul></ul><ul><ul><ul><li>Ice fields </li></ul></ul></ul><ul><ul><ul><ul><li>Ice fills elongated valleys along mountain ranges </li></ul></ul></ul></ul>
  6. 11. Glacial Processes <ul><li>Formation </li></ul><ul><ul><li>Zone of Accumulation: area above snowline where snow exists year-round </li></ul></ul><ul><ul><li>Snow accumulates in basins and becomes compacted under its own weight </li></ul></ul><ul><ul><ul><li>Snow becomes firn (compacted, granular snow) </li></ul></ul></ul><ul><ul><ul><li>Firn becomes glacial ice (exhibits strata from accumulation) </li></ul></ul></ul>
  7. 13. <ul><li>Mass Balance </li></ul><ul><ul><li>Above the snow line, in the Zone of Accumulation, mass is added to the glacier </li></ul></ul><ul><ul><li>Below the snow line, the glacial ice can melt, sublimate, deflate in the wind, or break off the main glacier </li></ul></ul><ul><ul><ul><li>Ablation or Waste are terms used to describe these losses </li></ul></ul></ul><ul><ul><ul><li>Zone of Ablation: the area below snowline where mass is lost from the glacier </li></ul></ul></ul><ul><ul><li>Mass balance refers to the rate of accumulation compared to the rate of ablation </li></ul></ul><ul><ul><ul><li>Positive balance: accumulation greater than ablation; glacier advances </li></ul></ul></ul><ul><ul><ul><li>Negative balance: ablation exceeds accumulation; glacier retreats </li></ul></ul></ul><ul><ul><ul><li>With current climate change, the world’s glaciers are largely in retreat </li></ul></ul></ul><ul><ul><ul><li>When rates of accumulation and ablation are equal, glacial movement continues to occur, but there is no net advance or retreat </li></ul></ul></ul>
  8. 17. <ul><li>Glacial Movement </li></ul><ul><ul><li>Simultaneous sliding and oozing motion </li></ul></ul><ul><ul><li>Frictional movement </li></ul></ul><ul><ul><ul><li>glacial ice rubs against bedrock on the sides and bottom of the valley </li></ul></ul></ul><ul><ul><ul><li>Abrasion and Plucking (erosional process) </li></ul></ul></ul><ul><ul><ul><li>Lateral and medial moraines (transportation features) </li></ul></ul></ul><ul><ul><li>Plastic movement </li></ul></ul><ul><ul><ul><li>glacier moves faster internally than along frictional edges </li></ul></ul></ul><ul><ul><ul><li>Causes cracks (crevasses) to form on the surface </li></ul></ul></ul><ul><ul><li>Surges </li></ul></ul><ul><ul><ul><li>Glaciers have been known to move several meters in one day </li></ul></ul></ul><ul><ul><ul><li>requires either large accumulations of mass, or lubricating meltwaters along the sides and bottoms </li></ul></ul></ul>
  9. 20. Glacial Landforms <ul><li>Erosion </li></ul><ul><ul><li>Plucking </li></ul></ul><ul><ul><li>Abrasion </li></ul></ul><ul><li>Transportation </li></ul><ul><ul><li>Surface load </li></ul></ul><ul><ul><li>Suspended load (englacial transport) </li></ul></ul><ul><ul><li>Along margins </li></ul></ul><ul><li>Deposition </li></ul><ul><ul><li>Occurs as a result of ablation </li></ul></ul><ul><ul><li>Melting and outwash sort transported material by mass and texture </li></ul></ul><ul><ul><ul><li>Larger objects deposited in situ </li></ul></ul></ul><ul><ul><ul><li>Smaller sediments carried out by outwash </li></ul></ul></ul>
  10. 26. <ul><li>Erosional Features of Alpine Glaciers </li></ul><ul><ul><li>Modified upslope drainage </li></ul></ul><ul><ul><ul><li>U-shaped valleys </li></ul></ul></ul><ul><ul><ul><li>Horns </li></ul></ul></ul><ul><ul><ul><li>Ar ê tes </li></ul></ul></ul><ul><ul><ul><li>Cirques </li></ul></ul></ul><ul><ul><ul><li>Hanging valleys </li></ul></ul></ul><ul><ul><ul><li>Tarns and paternoster lakes </li></ul></ul></ul><ul><ul><ul><li>Fjords </li></ul></ul></ul>
  11. 50. <ul><li>Depositional Features of Alpine Glaciers </li></ul><ul><ul><li>Glacial Drift </li></ul></ul><ul><ul><ul><li>Deposits of transported material (cobbles and finer sediment) </li></ul></ul></ul><ul><ul><ul><ul><li>Stratified drift: deposited by melt waters, sorted by size </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Glacial till: unsorted material deposited in place by ice </li></ul></ul></ul></ul><ul><ul><li>Moraines </li></ul></ul><ul><ul><ul><li>Deposition of glacial till by retreating glaciers </li></ul></ul></ul><ul><ul><ul><li>Rapid ablation causes till to be dispersed over a surface, creating a ground moraine or till plain </li></ul></ul></ul><ul><ul><ul><li>Slowing retreats (punctuated by periods of equilibrium) concentrate deposits of till </li></ul></ul></ul><ul><ul><ul><ul><li>terminal moraines mark the farthest extent of glacial advance </li></ul></ul></ul></ul><ul><ul><ul><ul><li>recessional moraines mark periods of slowing retreat during periods of general retreat </li></ul></ul></ul></ul>
  12. 54. <ul><li>Features of Continental Glaciation </li></ul><ul><ul><li>Erosional features </li></ul></ul><ul><ul><ul><li>deranged drainage </li></ul></ul></ul><ul><ul><ul><li>roche moutonn é e </li></ul></ul></ul><ul><ul><li>Depositional features </li></ul></ul><ul><ul><ul><li>Terminal and recessional moraines </li></ul></ul></ul><ul><ul><ul><li>Till plain, outwash plain </li></ul></ul></ul><ul><ul><ul><li>Eskers </li></ul></ul></ul><ul><ul><ul><li>Kettles </li></ul></ul></ul><ul><ul><ul><li>Kames </li></ul></ul></ul><ul><ul><ul><li>Drumlins </li></ul></ul></ul>
  13. 63. Periglacial Landscapes <ul><li>Features of Subarctic and Polar (tundra) climates that are not directly related to glaciation </li></ul><ul><li>Processes </li></ul><ul><ul><li>Physical weathering </li></ul></ul><ul><ul><li>Mass movement </li></ul></ul><ul><ul><li>Climate </li></ul></ul><ul><ul><li>Soil </li></ul></ul><ul><li>Features </li></ul><ul><ul><li>Permafrost </li></ul></ul><ul><ul><li>frost action </li></ul></ul><ul><ul><li>ground ice </li></ul></ul>
  14. 64. <ul><li>Permafrost </li></ul><ul><ul><li>develops after soil and rock have been below freezing for at least 2 consecutive years </li></ul></ul><ul><ul><ul><li>Independent of moisture content of the soil </li></ul></ul></ul><ul><ul><ul><li>snow cover insulates the ground, preventing heat loss </li></ul></ul></ul><ul><ul><li>Continuous and Discontinuous Zones of permafrost </li></ul></ul><ul><ul><ul><li>Continuous Zone </li></ul></ul></ul><ul><ul><ul><ul><li>Permafrost occurs everywhere, continuously, throughout this region </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Occurs pole-ward of the –7 o C mean annual temperature isotherm </li></ul></ul></ul></ul><ul><ul><ul><li>Discontinuous Zone </li></ul></ul></ul><ul><ul><ul><ul><li>Occurs equator-ward of the –7 o C mean annual temperature isotherm </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Permafrost becomes patchy and disconnected, becoming sparser at lower latitudes (mixed landscape of cryotic and noncryotic soil) </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Patches occur on slopes facing away from the sun (North slopes in N. Hemisphere), cold soil, or areas not blanketed by snow </li></ul></ul></ul></ul>
  15. 67. <ul><ul><li>Permafrost behavior </li></ul></ul><ul><ul><ul><li>Active layer: exposed to daily and seasonal freezes and thaws </li></ul></ul></ul><ul><ul><ul><ul><li>active layer thickens with increases in temperature </li></ul></ul></ul></ul><ul><ul><ul><li>Thawing releases carbon dioxide into the air </li></ul></ul></ul><ul><ul><ul><li>Taliks </li></ul></ul></ul><ul><ul><ul><ul><li>areas of noncryotic soil within areas of continuous permafrost </li></ul></ul></ul></ul><ul><ul><ul><ul><li>taliks form links with groundwater, permafrost disrupts these links </li></ul></ul></ul></ul>
  16. 68. <ul><li>Ground Ice and Frozen Ground </li></ul><ul><ul><li>Refers to frozen subsurface water </li></ul></ul><ul><ul><ul><li>Pore Ice </li></ul></ul></ul><ul><ul><ul><li>Lenses and Veins </li></ul></ul></ul><ul><ul><ul><li>Segregated Ice </li></ul></ul></ul><ul><ul><ul><li>Intrusive Ice </li></ul></ul></ul><ul><ul><ul><li>Wedge Ice </li></ul></ul></ul><ul><ul><li>Frost Action </li></ul></ul><ul><ul><ul><li>expansion of water as it freezes creates physical forces </li></ul></ul></ul><ul><ul><ul><ul><li>Shatters rock, creating block fields or felsenmeer </li></ul></ul></ul></ul><ul><ul><ul><ul><li>perturbs the soils </li></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Frost heaving </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Frost thrusting </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>cryoturbation </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Ice wedging </li></ul></ul></ul></ul></ul>
  17. 69. <ul><ul><li>Landforms </li></ul></ul><ul><ul><ul><li>Pingos: frozen injected artesian water, forming a circular mound, sometimes up to 60 m in height </li></ul></ul></ul><ul><ul><ul><li>Palsas: Mounds of peat with ice lenses (1 – 10 m) </li></ul></ul></ul><ul><ul><ul><li>Patterned ground: heaving and thrusting of the soil sorts the particles according to texture, with accumulations in wedge cracks, forming polygonal patterns on the ground </li></ul></ul></ul><ul><ul><li>Hillslope Processes </li></ul></ul><ul><ul><ul><li>Active layer becomes saturated with water during thaw cycles, and a slow downhill flow can occur </li></ul></ul></ul><ul><ul><ul><li>solifluction, gelifluction </li></ul></ul></ul><ul><ul><li>Thermokarst landscapes </li></ul></ul><ul><ul><ul><li>Formed from melting ground ice with poor drainage </li></ul></ul></ul><ul><ul><ul><li>cave-ins, bogs, depressions, standing water and small lakes </li></ul></ul></ul><ul><ul><ul><li>not related to carbonated Karst topography </li></ul></ul></ul>
  18. 76. The Pleistocene <ul><li>1.8 million to 10,000 years ago </li></ul><ul><ul><li>Ice sheets and glaciers covered 1/3 of Earth’s surface </li></ul></ul><ul><ul><li>Periglacial regions occupied another 40% </li></ul></ul><ul><li>The longest prolonged cold period in Earth’s history </li></ul><ul><ul><li>Ice Age: period of prolonged cold marked by significant periods of glacial advance </li></ul></ul><ul><ul><ul><li>glacials: 90,000 years </li></ul></ul></ul><ul><ul><ul><li>interglacials: 10,000 years </li></ul></ul></ul><ul><ul><li>Pleistocene included 18 glacials </li></ul></ul>
  19. 81. <ul><li>Features </li></ul><ul><ul><li>Formation of the Great Lakes </li></ul></ul><ul><ul><ul><li>Drainage systems enlarged by glacial action </li></ul></ul></ul><ul><ul><ul><li>Two periods of advance and retreat </li></ul></ul></ul><ul><ul><li>Charging of the Great Plains Aquifer </li></ul></ul><ul><ul><li>Land Bridges </li></ul></ul><ul><ul><ul><li>Lower temperatures caused more of Earth’s water to be tied up in ice </li></ul></ul></ul><ul><ul><ul><li>Sea levels were 100 meters lower than today </li></ul></ul></ul><ul><ul><ul><li>Exposed land, linking several continents, allowing for movement of species, especially humans </li></ul></ul></ul><ul><ul><ul><ul><li>Bering Straits Land Bridge </li></ul></ul></ul></ul><ul><ul><ul><ul><li>England and France </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Australia, New Guinea and Indonesia </li></ul></ul></ul></ul><ul><ul><li>Paleolakes </li></ul></ul><ul><ul><ul><li>Advance of glaciers caused an advance of polar conditions, subpolar lows and polar jet stream, bringing wetter conditions further south </li></ul></ul></ul><ul><ul><ul><ul><li>Pluvials </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Interpluvials </li></ul></ul></ul></ul><ul><ul><ul><li>Much of the American Southwest exhibited large lakes that are now dry </li></ul></ul></ul>
  20. 84. Paleoclimatology <ul><li>The study of past climates and their change over time </li></ul><ul><ul><li>Ice cores </li></ul></ul><ul><ul><li>Ocean sediments </li></ul></ul><ul><ul><li>pollen records </li></ul></ul><ul><ul><li>correlation of coral productivity to sea-level changes </li></ul></ul><ul><li>Humans evolved during the coldest parts of Earth’s history </li></ul><ul><li>Recent Fluctuations </li></ul><ul><ul><li>Medieval Warm Period: 800 – 1200 </li></ul></ul><ul><ul><li>Little Ice Age: 1200 – 1350, 1800 - 1900 </li></ul></ul>
  21. 86. <ul><li>Mechanisms of Climate Change </li></ul><ul><ul><li>Variations in Earth-Sun relations </li></ul></ul><ul><ul><ul><li>100,000 year cycle in variation of the shape of Earth’s orbit </li></ul></ul></ul><ul><ul><ul><ul><li>17.7 million km variation in Earth-Sun distance </li></ul></ul></ul></ul><ul><ul><ul><li>26,000 year cycle in precession </li></ul></ul></ul><ul><ul><ul><ul><li>affects axial parallelism </li></ul></ul></ul></ul><ul><ul><ul><li>40,000 year cycle in axial tilt </li></ul></ul></ul><ul><ul><ul><ul><li>varies between 22 o and 24 o </li></ul></ul></ul></ul><ul><ul><li>Solar variability: variation in solar output </li></ul></ul><ul><ul><li>Tectonics: movement of continents between latitudes </li></ul></ul><ul><ul><li>Atmospheric factors </li></ul></ul><ul><ul><ul><li>Volcanic eruptions </li></ul></ul></ul><ul><ul><ul><li>Fluctuations in CO 2 content </li></ul></ul></ul><ul><ul><li>Oceanic Circulation </li></ul></ul><ul><ul><ul><li>Formation of the Isthmus of Panama 3 million years ago altered the patterns of ocean currents, area of upwelling, and distribution of hot and cold ocean waters </li></ul></ul></ul>
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