October 16, 2011

Kötlujökull Retreat and Glacier Outburst floods

Posted by Mauri Pelto

Kötlujökull drains the southeast corner of the Mýrdalsjökull Ice Cap. This ice cap is centered around the Katla volcano, a subglacical volcano. The glacier descends from 1200 meters to 200 meters. This glacier advanced during the 1980’s creating a push moraine at the front (Kruger et al, 2002). In the 1990’s the glacier began to retreat. Kruger et al (2002) noted that during the 1990’s at the glacier front a 300-500 meters of dead ice formed. From 2000-2005 the glacier retreated 130 m (WGMS). There has been increased earthquake activity at Katla during 2011 as indicated in the diagram from the Icelandic Met Office, top image. The locations of the activity within the Katla Caldera is illustrated by the map from the Iceland Institute of Earth Sciences, bottom image. This has been associated with a couple of significant glacier outburst floods. In July a flood from Kötlujökull washed out the Highway 1 Ring Road bridge over the Múlakvísl. In 1973 the glacier had an active front during the early phase of its advance in this picture form Richard Williams (USGS).. Today the terminus features too indicators of retreat a zone of dead ice and now deglaciated terrain between the advance moraine and the present active ice. Beyond the 1980’s advance moraine is a flat outwash plain. The distance to the active ice from the former margin is 600 to 800 meters. During retreat the glacier has emplaced a number of recessional moraines. Recession is limited during the winter and a bit of a ridge is formed as sediment is pushed up and sediment is dumped at the terminus. The increased activity of Katla is being closed watched for an eruption as it often erupts after the which erupted in 2010. We often imagine the heat of a volcano will completely melt a glacier, however, this is not case with the ice caps in Iceland, which is an indication of just how much ice there is and the amount of heat needed to melt it. Recent eruptions did not remove either Gígjökull of Eyjafjallajökull Ice cap orSkeiðarárjökull Glacier