Glaciers and Rivers of Iceland - California Institute of ...web.gps.caltech.edu/~clay/Iceland/Talks/Glaciers_Rivers-Iceland.pdf · Facts about Glaciers • Glaciers form where: –

Glaciers and Rivers of Iceland

https://notendur.hi.is/~oi/icelandic_glaciers.htm

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/

http://en.wikipedia.org/wiki/File:Iceland_location_map.svg

Glaciers cover ~11% of Iceland!

http://visibleearth.nasa.gov/view.php?id=62109

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

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

http://en.wikipedia.org/wiki/Ice_cap#mediaviewer/File:Vatnaj%C3%B6kull.jpeg

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

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

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

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

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.

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.

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

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

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.

Björnsson, Helgi. "Subglacial lakes and jökulhlaups in Iceland." Global and Planetary Change 35.3 (2003): 255-271.

Peak discharge 40,000 m3/s

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

Jökulhlaup!

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

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

Highest Flow Rate River: Ölfusáá

http://www.grida.no/photolib/detail/river-olfus-just-north-of-selfoss-south-iceland_f0f1

440 m3/s

• https://www.youtube.com/watch?v=fJII-u-41Lg

Jökulhlaup!