Glacial processes and landforms NGEA01, 2014 Cecilia Akselsson Department of Physical Geography and Ecosystem Science Lund University
Geomorphological processes and landforms all over the world Periglacial processes Polygon wedge ice: Svalbard Glacial processes Esker: Dalarna, Sweden Photo: Jonas Åkerman Photo: Jonas Åkerman Endogene processes Volcano, Mexico Mass movements, fluvial processes, coastal processes Braided channel, New Zeeland From Hess, 2013 From Hess, 2013 Erosion and eolian processes Dunes: Namibia From Hess, 2013
Litterature The chapter Glacial modification of terrain
Swedish soils and many of the landforms: Formed by the ice ages
Glacial landforms young in earth history
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
Pleistoscene glacial and interglacial periods (From Wikipedia)
Pleistoscene glaciation maximum extent -Covered 1/3 of the land surface, up to several 1000 m thick
Pleistoscene glaciation maximum extent
Pleistoscene glaciation maximum extent
Today s extent -Covers 10% of the land area
Two types of glaciers: 1.Mountain glaciers -a few 100 to a few 1000 km 2 ice sheets high elevations -E.g in western Canada, southern Alaska, Iceland, northern Scandinavia (From Hess, 2013)
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
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
Glacial formation
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
Glacier movement
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
Landforms caused by continental ice sheets
Landforms caused by continental ice sheets Erosion: Roche moutonnée (rundhäll)
Landforms caused by continental ice sheets Deposition: Moraines -Composed of till -a few m to a few 100 m high -terminal moraines (ändmorän), recessional moraines (recessionsmorän) -ground moraine (bottenmorän)
Landforms caused by continental ice sheets Deposition: Drumlins -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
Landforms caused by continental ice sheets Deposition: Kettles (dödisgropar)
Landforms caused by continental ice sheets Glacifluvial: Kames
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 km 2 -Often kettles and ponds
Landforms caused by continental ice sheets Glacifluvial: Eskers (rullstensåsar) (Photo: Jonas Åkerman) (Photo: Jonas Åkerman)
Landforms caused by mountain glaciers
Landforms caused by mountain glaciers Erosion: Cirques (nischer)
Landforms caused by mountain glaciers Erosion: Horns
Landforms caused by mountain glaciers Erosion: Glacial troughs (U-dal) (Photo: Jonas Åkerman)
Landforms caused by mountain glaciers Deposition: Lateral moraines (sidomoräner)
Indirect effects of glaciation -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
The development of the Baltic sea during ice retreat 10 200 BP 9 800 BP 9 500 BP 6 500 BP (skoltips.wordpress.com)
Soil types in Sweden
Land use in Sweden
Isostatic adjustment in Sweden 36
Exogene processes strongly linked to climate change! Periglacial processes Polygon wedge ice: Svalbard Glacial processes Esker: Dalarna, Sweden Photo: Jonas Åkerman Photo: Jonas Åkerman Endogene processes Volcano, Mexico Mass movements, fluvial processes, coastal processes Braided channel, New Zeeland From Hess, 2013 From Hess, 2013 Erosion and eolian processes Dunes: Namibia From Hess, 2013
Movie time!