glaciers and rivers of iceland - california institute of...
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Glaciers and Rivers of Iceland
https://notendur.hi.is/~oi/icelandic_glaciers.htm
Gígjökull
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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/
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www.vedur.is/skjol/03037.pdf
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http://www.vedur.is/vedur/vedurfar/kort/medalurkoma_arsins/
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http://en.wikipedia.org/wiki/File:Iceland_location_map.svg
Glaciers cover ~11% of Iceland!
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http://visibleearth.nasa.gov/view.php?id=62109
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Glacial Retreat
https://notendur.hi.is/~oi/icelandic_glaciers.htm
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
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Types of Glaciers
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Ice Caps • Cover less than 50000 km2
• Not bounded by topography
– (that would be an ice field)
• Ice flows away from highest point
http://en.wikipedia.org/wiki/Ice_cap#mediaviewer/File:Vatnaj%C3%B6kull.jpeg
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Outlet Glacier
Sólheimajökull
http://www.usgs.gov/blogs/features/usgs_top_story/a-cold-look-at-planet-earth-learning-from-the-worlds-frozen-places/
Flow away from the glacial dome Usually confined to valleys and broad subglacial channels
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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)
http://www.onegeology.org/extra/kids/earthprocesses/alpineGlaciers.html#
Near Holar, northern Iceland
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Piedmont Glacier Where valley glaciers spill out onto flat pains and form bulb like shapes
Múlajökull
Hofsjökull
http://blogs.agu.org/mountainbeltway/2010/10/17/litter-of-drumlins/
http://en.wikipedia.org/wiki/Glacier_morphology#Piedmont_glaciers
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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.
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Drumlins
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
elliptical hills of glacial till Only known active drumlin formation at Múlajökull surge type outlet
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.
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More About Drumlins
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
Working hypothesis about drumlin formation from Johnston et al: 1. 2. 3. 4.
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Glacial Flutes & Eskers
https://notendur.hi.is//~oi/index.htm
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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
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Moraines
https://notendur.hi.is//~oi/index.htm
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
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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.
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Björnsson, Helgi. "Subglacial lakes and jökulhlaups in Iceland." Global and Planetary Change 35.3 (2003): 255-271.
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Björnsson, Helgi. "Subglacial lakes and jökulhlaups in Iceland." Global and Planetary Change 35.3 (2003): 255-271.
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Björnsson, Helgi. "Subglacial lakes and jökulhlaups in Iceland." Global and Planetary Change 35.3 (2003): 255-271.
Peak discharge 40,000 m3/s
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https://volcanocafe.wordpress.com/2013/08/16/kickem-gumbo-ntv-riddle-9/comment-page-1/
Jökulhlaup!
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http://www.stjornufraedi.is/solkerfid/jordin/joklar/jokulhlaup/
Jökulhlaup!
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http://hudsonvalleygeologist.blogspot.com/2010_04_01_archive.html
Jökulhlaup!
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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
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jökulár
http://images.fineartamerica.com/images-medium-large/1-braided-river--skeidararsandur--iceland-phil-degginger.jpg
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Longest River in Iceland: Þjórsá
http://www.timinn.is/media/202070/tjorsa.gif
http://www.anglers.is/index.php/about-fishing-in-iceland/about-icelandic-rivers-and-lakes
237 km 380 m3/s
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Highest Flow Rate River: Ölfusáá
http://www.grida.no/photolib/detail/river-olfus-just-north-of-selfoss-south-iceland_f0f1
440 m3/s
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• https://www.youtube.com/watch?v=fJII-u-41Lg
Jökulhlaup!