https://notendur.hi.is/~oi/icelandic_glaciers.htm
Glaciers and Rivers of Iceland
Gígjökull
Facts about Glaciers
• Glaciers form where:
– the mean T is < 0 over many
years
– More snow than melt
(In Iceland this means that they form
at elevations >60-80m where
precipitation is high)
• Glaciers are the largest reservoir of
freshwater
• Temperate v. cold
• There are many types of glaciers
– 4 of these are found in Iceland
ice caps, piedmont, outlet, cirque
http://www.wilderness-survival.net/movement-snow-ice/glacial-walking/
www.vedur.is/skjol/03037.pdf
http://www.vedur.is/vedur/vedurfar/kort/medalurkoma_arsins/
Glaciers cover ~11% of Iceland!
http://en.wikipedia.org/wiki/File:Iceland_location_map.svg
http://visibleearth.nasa.gov/view.php?id=62109
Glacial Retreat
Little ice age extension 1890-1920
Warmer climate -> quick retreat
1930-1940
Cooler climate -> slow retreat
1940-1970
Retreat apparently caused by
warming b.c. no change in precip.
Loss of ~0.2 % per year
-> 500 years left
https://notendur.hi.is/~oi/icelandic_glaciers.htm
Types of Glaciers
Ice Caps
• Cover less than 50000 km2
• Not bounded by topography
– (that would be an ice field)
• Ice flows away from highest point
Outlet Glacier
Flow away from the glacial dome
Usually confined to valleys and broad subglacial channels
Sólheimajökull
http://www.usgs.gov/blogs/features/usgs_top_story/a-cold-look-at-planet-earth-learning-from-the-worlds-frozen-places/
Cirque Glaciers
Form in bowl shaped depressions on the sides of mountains
Can form from accumulation of avalanches
If they extend beyond the bowl they become outlet glaciers
If there is significant amount of rocks falling on them they become rock glaciers
When a mountain is surrounded by cirque glaciers it becomes really steep and is called a
horn (for example the Matterhorn)
Near Holar, northern Iceland
http://www.onegeology.org/extra/kids/earthprocesses/alpineGlaciers.html#
Piedmont Glacier
Where valley glaciers spill out onto flat pains and form bulb like shapes
Hofsjökull
Múlajökull
http://blogs.agu.org/mountainbeltway/2010/10/17/litter-of-drumlins/
http://en.wikipedia.org/wiki/Glacier_morphology#Piedmont_glaciers
Glacial Features
Evans, David JA, and Brice R. Rea. "Geomorphology and sedimentology of surging glaciers: a
land-systems approach." Annals of Glaciology 28.1 (1999): 75-82.
Drumlins
elliptical hills of glacial till
Only known active drumlin
formation at Múlajökull
surge type outlet
Johnson, M., Schomacker, A., Benediktsson, I., Geiger, A., Ferguson, A., & Ingolfsson, O. (2010).
Active drumlin field revealed at the margin of Mulajokull, Iceland: A surge-type glacier Geology,
38 (10), 943-946
Evans, David JA, and Brice R. Rea. "Geomorphology and sedimentology of surging glaciers: a
land-systems approach." Annals of Glaciology 28.1 (1999): 75-82.
More About Drumlins
Working hypothesis about
drumlin formation from
Johnston et al:
1.
2.
3.
4.
Johnson, M., Schomacker, A., Benediktsson, I., Geiger, A., Ferguson, A., & Ingolfsson, O. (2010).
Active drumlin field revealed at the margin of Mulajokull, Iceland: A surge-type glacier Geology,
38 (10), 943-946
Glacial Flutes & Eskers
https://notendur.hi.is//~oi/index.htm
Aretes
Long ridges formed when two outlet glaciers parallel each other
Eyjafjodur, north of Akureyri, Iceland
http://www.onegeology.org/extra/kids/earthprocesses/alpineGlaciers.html
Moraines
Accumulation of unconsolidated glacial debris
Can be composed of particles ranging in size from silt sized glacial “flour” to boulders
Clasts are typically sub angular to rounded
https://notendur.hi.is//~oi/index.htm
Jökulhlaups!
“yer-kul-hloyp”, “YO-kel-yawp” and “yo-kul-h-loip” in varying pronunciations
Glacial outburst flood
Can be caused by volcanic activity beneath a glacier
Can also be caused by meltwater escape from geothermal activity
The sudden release of pressure from a jökulhlaup can cause volcanic activity.
November 5 though 8, 1996
jökulhlaup that burst from the Skeiararjokull Glacier
following a sub-glacial volcanic eruption
discharge of 5,000 cubic meters per second just after eruption
increased to 15,000 cubic meters per second within 90 minutes.
Two large bridges were destroyed
ice canyon 6 kilometers long with an average depth of 100 meters.
Björnsson, Helgi. "Subglacial lakes and jökulhlaups in Iceland." Global and Planetary Change 35.3
(2003): 255-271.
Björnsson, Helgi. "Subglacial lakes and jökulhlaups in Iceland." Global and Planetary Change 35.3
(2003): 255-271.
Peak discharge
40,000 m3/s
Björnsson, Helgi. "Subglacial lakes and jökulhlaups in Iceland." Global and Planetary Change 35.3
(2003): 255-271.
Jökulhlaup!
https://volcanocafe.wordpress.com/2013/08/16/kickem-gumbo-ntv-riddle-9/comment-page-1/
Jökulhlaup!
http://www.stjornufraedi.is/solkerfid/jordin/joklar/jokulhlaup/
Jökulhlaup!
http://hudsonvalleygeologist.blogspot.com/2010_04_01_archive.html
Rivers in Iceland
• 3 types
– Debris-laden glacial rivers (jökulár)
• Peak flow in summer
• 2000 ppm glacial silt
– Direct run-off rivers (dragár)
• Peak flow in summer and autumn
• Common on older rocks
– Spring-fed rivers (lindár)
•
•
•
•
Constant flow throughout year
Waterfalls common in these
Common on postglacial lava fields
Narrow and deep channels
http://www.randburg.com/is/general/general_19.html
http://www.anglers.is/index.php/about-fishing-in-iceland/about-icelandic-rivers-and-lakes
jökulár
http://images.fineartamerica.com/images-medium-large/1-braided-river--skeidararsandur--iceland-phil-degginger.jpg
Longest River in Iceland:
Þjórsá
237 km
380 m3/s
http://www.timinn.is/media/202070/tjorsa.gif
http://www.anglers.is/index.php/about-fishing-in-iceland/about-icelandic-rivers-and-lakes
Highest Flow Rate River: Ölfusáá
440 m3/s
http://www.grida.no/photolib/detail/river-olfus-just-north-of-selfoss-south-iceland_f0f1
Jökulhlaup!
• https://www.youtube.com/watch?v=fJII-u41Lg