cecilia akselsson department of physical geography and ...lund university, deparment of physical...

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


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


From Hess, 2013

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

(From Hess, 2013)


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

(From Hess, 2013)

-Covered 1/3 of the land surface, up to several 1000 m thick


Pleistoscene glaciation – maximum extent

(From Hess, 2013)


Today´s extent

(From Hess, 2013)

-Covers 10% of the land area


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)


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

(From Hess, 2013)


Glacial formation

(From Hess, 2013)


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

(From Hess, 2013)


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

(From Hess, 2013)


Landforms caused by continental ice sheets Erosion: Roche moutonnée (rundhäll)

(From Hess, 2013)


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)


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


Landforms caused by continental ice sheets Deposition: Kettles (dödisgropar)

(From Hess, 2013)


Landforms caused by continental ice sheets Glacifluvial: Kames

(From Hess, 2013)


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


Landforms caused by continental ice sheets Glacifluvial: Eskers (rullstensåsar)

(From Hess, 2013) (Photo: Jonas Åkerman)

(Photo: Jonas Åkerman)


Landforms caused by mountain glaciers

(From Hess, 2013)


Landforms caused by mountain glaciers Erosion: Cirques (nischer)

(From Hess, 2013)


Landforms caused by mountain glaciers Erosion: Horns

(From Hess, 2013)


Landforms caused by mountain glaciers Erosion: Glacial troughs (U-dal)

(Photo: Jonas Åkerman)


Landforms caused by mountain glaciers Deposition: Lateral moraines (sidomoräner)

(From Hess, 2013)


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


The development of the Baltic sea during ice retreat

(skoltips.wordpress.com)

10 200 BP 9 800 BP

9 500 BP 6 500 BP


Soil types in Sweden


Land use in Sweden


36

Isostatic adjustment in Sweden


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



From Hess, 2013

From Hess, 2013


Movie time!

cecilia akselsson department of physical geography and ...lund university, deparment of physical...

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