Cecilia Akselsson Department of Physical Geography and ...Lund University, Deparment of Physical...
Transcript of Cecilia Akselsson Department of Physical Geography and ...Lund University, Deparment of Physical...
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Lund University, Deparment of Physical Geography and Ecosystem Science
Glacial processes and landforms NGEA01, 2014
Cecilia Akselsson
Department of Physical Geography and Ecosystem Science
Lund University
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Lund University, Deparment of Physical Geography and Ecosystem Science
Geomorphological processes and landforms all over the world
Glacial processes Esker: Dalarna, Sweden
Periglacial processes Polygon wedge ice: Svalbard
Erosion and eolian processes Dunes: Namibia
Endogene processes Volcano, Mexico
Mass movements, fluvial processes, coastal processes Braided channel, New Zeeland
From Hess, 2013
Photo: Jonas Åkerman
Photo: Jonas Åkerman
From Hess, 2013
From Hess, 2013
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Lund University, Deparment of Physical Geography and Ecosystem Science
Litterature
The chapter “Glacial modification of terrain”
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Lund University, Deparment of Physical Geography and Ecosystem Science
Swedish soils and many of the landforms: Formed by the ice ages
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Lund University, Deparment of Physical Geography and Ecosystem Science
Glacial landforms – young in earth history
(From Hess, 2013)
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Lund University, Deparment of Physical Geography and Ecosystem Science
The Quaternary period: started 2 600 000 years ago (The age of the earth: 4 600 000 000 years)
-Several ice ages during the quaternary period
-Last one: Weichsel 110 000-10 000 years ago
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Lund University, Deparment of Physical Geography and Ecosystem Science
Pleistoscene – glacial and interglacial periods
(From Wikipedia)
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Lund University, Deparment of Physical Geography and Ecosystem Science
Pleistoscene glaciation – maximum extent
(From Hess, 2013)
-Covered 1/3 of the land surface, up to several 1000 m thick
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Lund University, Deparment of Physical Geography and Ecosystem Science
Pleistoscene glaciation – maximum extent
(From Hess, 2013)
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Lund University, Deparment of Physical Geography and Ecosystem Science
Pleistoscene glaciation – maximum extent
(From Hess, 2013)
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Lund University, Deparment of Physical Geography and Ecosystem Science
Today´s extent
(From Hess, 2013)
-Covers 10% of the land area
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Lund University, Deparment of Physical Geography and Ecosystem Science
Two types of glaciers: 1.Mountain glaciers
-a few 100 to a few 1000 km2
ice sheets high elevations
-E.g in western Canada, southern Alaska, Iceland, northern Scandinavia…
(From Hess, 2013)
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Lund University, Deparment of Physical Geography and Ecosystem Science
Two types of glaciers: 2. Continental ice sheets
-Glaciers forming in non-mountainous areas, great depths (up to several 1000 meters)
-Pleistoscene: Covered vast areas
-Today: two ice sheets, Antarctica and Greenland
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Lund University, Deparment of Physical Geography and Ecosystem Science
Glacial formation
-Requires accumulation of snow (more snowfall in the winter than what is melted in the summer.
-Snow turns to ice by the pressure
-Ice movement starts
(From Hess, 2013)
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Lund University, Deparment of Physical Geography and Ecosystem Science
Glacial formation
(From Hess, 2013)
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Lund University, Deparment of Physical Geography and Ecosystem Science
Glacier movement
-Plastic flow: When ice thickness > 50 m (or less at steep slopes)
-Basal slip: The ice slides over a film of water
-The rates are a few cm/day or in some cases a few m/day
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Lund University, Deparment of Physical Geography and Ecosystem Science
Glacier movement
(From Hess, 2013)
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Lund University, Deparment of Physical Geography and Ecosystem Science
Effects of glaciers - processes
• Erosion -Glacial plucking
-Glacial abrasion -Subglacial meltwater erosion
• Transport -Transport at the base of the ice or on the top
-Melt streams
• Deposition -Direct deposition by glacial ice -Secondary deposition by meltwater
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Lund University, Deparment of Physical Geography and Ecosystem Science
Landforms caused by continental ice sheets
(From Hess, 2013)
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Lund University, Deparment of Physical Geography and Ecosystem Science
Landforms caused by continental ice sheets Erosion: Roche moutonnée (rundhäll)
(From Hess, 2013)
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Lund University, Deparment of Physical Geography and Ecosystem Science
Landforms caused by continental ice sheets Deposition: Moraines
(From Hess, 2013)
-Composed of till
-a few m to a few 100 m high
-terminal moraines (ändmorän), recessional moraines (recessionsmorän)
-ground moraine (bottenmorän)
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Lund University, Deparment of Physical Geography and Ecosystem Science
Landforms caused by continental ice sheets Deposition: Drumlins
(From Hess, 2013)
-Low, elongated hills of unsorted till in the ice movement direction
-Steeper slope towards ice front
-Formed when ice readvance in an area with previous glacial deposition
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Lund University, Deparment of Physical Geography and Ecosystem Science
Landforms caused by continental ice sheets Deposition: Kettles (dödisgropar)
(From Hess, 2013)
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Lund University, Deparment of Physical Geography and Ecosystem Science
Landforms caused by continental ice sheets Glacifluvial: Kames
(From Hess, 2013)
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Lund University, Deparment of Physical Geography and Ecosystem Science
Landforms caused by continental ice sheets Glacifluvial: Outwash plains (sandur)
-Deposits from melt water from the ice. Sediments are deposited, a channel system is created
-Can cover several 100 km2
-Often kettles and ponds
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Lund University, Deparment of Physical Geography and Ecosystem Science
Landforms caused by continental ice sheets Glacifluvial: Eskers (rullstensåsar)
(From Hess, 2013) (Photo: Jonas Åkerman)
(Photo: Jonas Åkerman)
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Lund University, Deparment of Physical Geography and Ecosystem Science
Landforms caused by mountain glaciers
(From Hess, 2013)
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Lund University, Deparment of Physical Geography and Ecosystem Science
Landforms caused by mountain glaciers Erosion: Cirques (nischer)
(From Hess, 2013)
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Lund University, Deparment of Physical Geography and Ecosystem Science
Landforms caused by mountain glaciers Erosion: Horns
(From Hess, 2013)
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Lund University, Deparment of Physical Geography and Ecosystem Science
Landforms caused by mountain glaciers Erosion: Glacial troughs (U-dal)
(Photo: Jonas Åkerman)
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Lund University, Deparment of Physical Geography and Ecosystem Science
Landforms caused by mountain glaciers Deposition: Lateral moraines (sidomoräner)
(From Hess, 2013)
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Lund University, Deparment of Physical Geography and Ecosystem Science
Indirect effects of glaciation
(From Hess, 2013)
-Sea level changes: At Pleistoscene maximum global sea level 130 meters lower than now. Affects drainage and landforms.
-Crustal depression: Earth crust has sunk due to high load. Isostatic adjustment in progress in Canada and northern Europe
-Increased moisture due to more meltwater, less evaporation, increased precipitation. Many lakes were formed, parts left, and traces left on other places
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Lund University, Deparment of Physical Geography and Ecosystem Science
The development of the Baltic sea during ice retreat
(skoltips.wordpress.com)
10 200 BP 9 800 BP
9 500 BP 6 500 BP
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Lund University, Deparment of Physical Geography and Ecosystem Science
Soil types in Sweden
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Lund University, Deparment of Physical Geography and Ecosystem Science
Land use in Sweden
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Lund University, Deparment of Physical Geography and Ecosystem Science
36
Isostatic adjustment in Sweden
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Lund University, Deparment of Physical Geography and Ecosystem Science
Exogene processes strongly linked to climate change!
Glacial processes Esker: Dalarna, Sweden
Periglacial processes Polygon wedge ice: Svalbard
Erosion and eolian processes Dunes: Namibia
Endogene processes Volcano, Mexico
Mass movements, fluvial processes, coastal processes Braided channel, New Zeeland
From Hess, 2013
Photo: Jonas Åkerman
Photo: Jonas Åkerman
From Hess, 2013
From Hess, 2013
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Lund University, Deparment of Physical Geography and Ecosystem Science
Movie time!