On 30 Sept. 1996 a subglacial volcano erupted under the Vatnajokull ice cap. Subsequently on 5 Nov. at 08:00 meltwater reached the edge of the glacier fracturing it in several places. At 08:30 the water was 3-4 m high and 500-600 m across issued from the glaicer. At 23:00 that same night the peak discharge estimated to be 50,000 m3/sec was reached and the main flow was over by 16:00 the next day. This flood cut a canon into the ice margin some 1 km long, 250 m wide and 40 m deep. The flow carried icebergs at least 15 km away from the source.
In August 1998 Dave Mickelson and I lead field trips to view the resulting features in the rain. The gound images are a little dark and don't really convey the size of the features. Of most interest then are air images from Warren Huff. He took an airplane flight to view the effects of the flood and eruption. These images were scanned quickly with only simple post-processing.
If you would like to use any of these please contact him directly Warren.Huff@UC.EDU or contact me if you would like any additional information. Thomas.Lowell@uc.edu
Descriptions of each image follow but an overview web page is here.
WH5-18.JPG View of the outwash of Skeidarasandur. The glacier Skeidararjokull is off the left side of the image and the Skaftafell Park just to the right of the image.
WH5-19.JPG The eastern side of Skeidararjokull. The eastern outlet (Skeidara) is on the center left, and the path exits to the right. Most of the landscape is not impacted by the last flood. The kettled outwash in the foreground resulted from older events.
WH5-20.JPG A pan just to the east of the last image. The eastern outlet can be seen in the distance and a small outlet in the foreground. Darker area is the fresh sediments. The lake was present before the flood, but is lager now than before.
WH6-1.JPG View upglacier showing the crevasses and central part of the Vatbajokull ice cap beyond the mountains.
WH6-2.JPG Plane over the glacier looking to the south. The river Gigjukvisl now starts at the main outburst location swings inside the Little Ice Age moraine and then cuts through the moraine. The outwash along the glacier margin lies inside an Little Ice Age moraine. The moraine is cut to the left side of the image.
WH6-21.JPG View to the northeast. The Little Ice Age drift in the foreground has a green look from the vegetation. The flood deposits in the background are fresh black volcanic sands. Kettles and outwash channels can be seen on both surfaces.
WH6-22.JPG Same area as above with the ice margin (fractured) in the background. Notice a small fan from one of the secondary outlets. The main outlet is to the left of the image.
WH6-23.JPG The scarp separating the old and new surfaces. Approximately 40 m high. Notice the collapse along the edge of the scarp as it melting ice lies below the surface.
WH6-24.JPG The scarp again. Notice at least four generations of kettles. Oldest listed first: the small circular kettles in the upper (green) surface; the collapse kettles along the edge of the scarp; the circular kettles filled with water on the still forming after the flood; and the large lake in the outwash surface that has cut the fresh kettle drift.
WH6-25.JPG Detail of the new fans. Notice the color changes reflecting different source rocks or different grain size. Consider the markings around the isolated kettles in the lower part of the image. Would these be good indicators of flow?
WH6-27.JPG Some overlap with the above image. Notice that the distribution of the kettles is not random. The line along the bottom shows up in other images.
WH6-29.JPG View to the south showing the outlet canon. The glacier is in the lower part of the image and the scarp lies just at the top. The outlet has two horseshoe shapes - much like the cataracts at the head of the channeled scablands! Would you call this a inverse waterfall?
WH6-3.JPG Regional view to the south across the entire Skeidarasandur to the ocean in the distance. Glacier in the foreground. View west of the central outlet.
WH6-30.JPG Another view of the outlet canon. Consider the distribution of the kettles from this perspective. High channel cutting the upper surface has a coffer dam across it to protect the bridge downstream.
WH6-31.JPG Close up of the horseshoes. Notice how fractured the glacier is to the east (left) side of the outlet. In general the fractures reflect the shape of the canon telling us something about the strength of the ice. The canon is not at right angles to the ice margin.
WH6-33.JPG View of the canon toward the west. The reason for the distribution of the kettles should be clear now.
WH6-34.JPG View to the north of the ice margin with the horseshoes just on the right side. Notice the fractures in the ice and the smaller outlet just to the right off the aircraft wing. Some flow came from a source to the east.
WH6-35.JPG View directly up the flood flow direction. Why is that large piece of ice sticking out from the right side of the canon.
WH6-36.JPG Close up with the same orientation as above. What features indicating flow direction will be preserved?
WH6-37.JPG View of the canon to the east. Do the large fractures in the foreground indicate zones the glacier was cracked?
WH6-5.JPG View of the western margin of Skeidararjokull. The flood magnitude was not that large on this side of the glacier - this time!
The following are from positions up-glacier from the margin.
WH6-7.JPG View to the southeast. The great flood can not be seen from this distance.
WH7-05.JPG The great ice canon near the eruption site. The dark circular rings are collapse of the ice as it melted from below. The white is snow deposited after the eruption.
WH7-10.JPG Detail of the ice surface with superglacial stream channels and ash.
WH7-12.JPG View to the northeast across the glacier. The ice cap in the background.
