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The 1996 Iceland jökulhlaup

These pages cover the jökulhlaup (glacier-flood) which followed the 1996 subglacial eruption on the Vatnajökull ice sheet, Iceland.


The jökulhlaup, 5 November 1996 at 14:30

This one of several excellent new images of the jökulhlaup from The Science Institute, University of Iceland. The photographs were taken by Magnús Tumi Guðmundsson and Finnur Pálsson.

This is a view northwards, showing the easternmost part of the jökulhlaup, the 900 m long Skeiðará bridge and the dyke system protecting the Skaftafell National Park, which is situated to the east (left) of the river. At this time about 15,000 m³/s was flowing down this part of the alluvial plane. The bridge was still intact but a few hours later the easternmost end was washed away.

Hour by hour

The Science Institute, University of Iceland, reported the 1996 jökulhlaup, hour by hour:

November 5 1996 - 09:00 GMT

The jökulhlaup from Grímsvötn has just begun. The volume of the Skeiðará river is increasing rapidly this morning. A continuous high frequency tremor appeared on the station on Grímsfjall at 21:30 hours last night. The tremor amplitude increased steadily throughout the night and is about 16 times greater now at 9 am.

November 5 - 10:00 GMT

The road across Skeiðarársandur has been closed. The jökulhlaup now surrounds the 900 m long bridge across Skeiðará which has reached a flow rate of 6000 cubic m/s within the first 2 hours. "Icebergs" are breaking off the glacier snout and are being carried down with the flow.

November 5 - 13:00 GMT

According to radio reports, the bridge across one of the glacier rivers (Gígjukvísl) has now perished in the flood. The power line is down and the telephone fiber cables have been cut by the flood. The maximum tremor amplitude is around 240 units.

November 5 - 18:00 GMT

The bridge across Sæluhúsakvísl has been demolished by the flood and the longest bridge in Iceland, the 900 m long Skeiðará bridge is severely damaged as well, and not expected to last much longer. Glaciologists surveying the flood from an aircraft at 15 h estimated the flow rate to be around 25,000 cubic m/s. The maximum tremor is now 270 units. The Skeiðará bridge is worth 10 million US$. The total damage to constructions today is estimated at about 15 million US$.

November 6. - 9:00 GMT

The jökulhlaup culminated at 22:30 hours last night. At that time close to 45,000 cubic m/s flowed from Grímsvötn, along a 50 km long path beneath the outlet glacier Skeiðarárjökull out to the alluvial plane, Skeiðarársandur. The high frequency tremor recorded at Grímsfjall stayed fairly constant throughout the night and still has a maximum of 230 units. Although damaged, close to 700 m of the 900 m long Skeiðará bridge is still standing but the bridges across Sæluhúsakvísl and Gígjukvísl washed away. Skeiðará is the easternmost river draining this region whereas Sæluhúsakvísl and Gígjukvísl are the central bridges. The westernmost bridge, across Núpsvötn stayed intact. The initial (main) phase of the jökulhlaup, which begun at 8 h yesterday morning with a 3-5 m high water wave, flowed down the easternmost and central part of the Skeiðarársandur plain, not reaching Núpsvötn until afternoon yesterday. Many large icebergs (up to 200 tons) are scattered on the plain.

November 6 - 10:00 GMT

Correction: Latest reports claim that the bridge across Sæluhúsakvísl is still standing and that the jökulhlaup has decreased markedly.

November 7 - 12:00 GMT

The jökulhlaup has finished. The flowrate in the glacier rivers on Skeidarrsandur is now at 400 cubic m/s. At least 3 cubic km of water thick with ash and other fragments from the eruption have flowed from Grímsvötn, along the bottom of the glacier out to sea, within the last 52 hours. The water has left many huge icebergs, some are 10-15 m high weighing up to 1000 tons. The high frequency tremor recorded at the seismic station on Grimsfjall, on the southeastern rim of the Grímsvötn caldera, has decreased to less than 10 units. However, the instrument still records numerous "icequakes" which occur within the glacier as it is still being cracked in response to the sudden lowering of the iceshelf above the caldera lake.

November 8 1996 - 11:00 GMT

GPS measurements of the lake level at Grímsvötn showed it to be at 1345 m a.s.l. yesterday afternoon. Thus, the waterlevel subsided 165 m during the jökulhlaup. A 6 km long, 500 m wide and up to 200 m deep ice canyon has formed over the jökulhlaup outlet at the southeastern margin of Grímsvötn. The current subsidence is larger than during the April 1996 jökulhlaup, when the waterlevel subsided 74 m, from about 1454 m to 1380 m. This jökulhlaup carried up to 100 million tons of volcanic material and clay out to sea which could be traced up to 15 km out by its brown colour. It did, however, not trigger any lahars. Our seismic station at Grimsfjall still records numerous "icequakes" caused by collapsing crevasses and other glacier movement.

The Volcanological Institute also reported, on November 5 1996:

The river Skeiðará, originating in the subglacial lake of the Grímvötn caldera, has started to increase. At present the frost in Iceland is between -2 to -20 degrees Centigrade thus glacial rivers should be at a minimum. This morning, however, a scientist observed that the river Skeiðará was increasing its discharge. The river smells strongly of sulphur and the water is loaded with sediments. It is expected that the river will increase its discharge rate for the next couple of days, until it reaches a maximum of perhaps 20,000 to 30,000 m3/s. See this image for possible areas of flooding.

Iceland Review reported:

November 5 1996 - 1 pm:
A tidal wave of black melt water and huge chunks of ice from last month's Vatnajökull eruption is hurtling southwards under and over Europe's largest glacier sweeping aside everything in its path.

The giant flood, believed to be the greatest ever witnessed in Iceland, burst from the Lake Grimsvötn caldera between 8-9am today. Scientists estimate that an initial 3km3 water came crashing under the glacier before washing over the sandy plains of the south lands. Such is the force of the flood that it blasted a 2km long crevice 100m from the edge of the glacier spewing the murky water forth in waves over the frozen surface.

A bridge over the river Gýgja has succumbed to the flood along with a fibre optic telecommunications cable. The ring road linking the south and east of the country has been swept away in several places, most dramatically either side of the Skeidarár bridge, as engineers await the further destruction of bridges, roadway and power lines that is sure to follow in its wake. Meanwhile, vessels fishing in the waters off the south coast have been warned to haul in their gear as there is a danger of flood waves of silt sweeping over the ocean bed.
A detection of disturbance around 10:30pm yesterday picked up by measuring equipment at Grímsfjall, near the site of the eruption, sparked an initial warning although scientists were not sure whether what they were witnessing was a new sub-glacial eruption or that the colossal amount of melt-water was bursting through the ice dam of the Grímsvötn caldera. By early morning the measurement of disturbances grew ten-fold signalling that the wait for the flood was over. Within two hours, the volume of water had increased a hundred-fold.

November 5. 5pm:
"In just four hours this has knocked us back 20-30 years in terms of our road building endeavours," said Prime Minister Davíd Oddsson after flying over south Iceland witnessing first hand the damage resulting from the immense flood water of the Vatnajökull glacial eruption.
Scientists estimate the rate of water flooding the plains of the south to be gushing at a phenomenal 20,000 m3 per second and growing. Nobody has so far been able to say when the unstoppable wave of water will subside.
Large stretches of the ring road have been washed away with three bridges in very real danger of being destroyed, including one of the country's largest and most important. One bridge, that over the river Gýgja, has already been carried away by the tidal like flow of the glacial melt-water onslaught, costing the nation an estimated ISK300 million, around US$4.6 million, to replace.

The Scott Polar Research Institute maintains a database called ICE AND SNOW [Last updated February 2000]. This contains references from journals and books on glaciology, permafrost, sea ice, glacial geology, ice physics - indeed anything on ice or snow.

This is a subset of the SPRILIB database maintained at our library in Cambridge. Currently 16,000 monograph records may be searched.
Here is a small selection on the Vatnajökull ice sheet.

Other sources:

Sequence of eruption events

Early images:

Map of the area

Map of the area - courtesy of Vokfilm, Iceland

Links and further information

The Nordic Volcanological Institute, Iceland, is a Nordic institute for research and training in volcanology and related fields. See their information on the eruption.

Additional useful links:

Copyright information

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