In more modern times, the volcanoes continue to erupt beneath the glaciers, resulting in many documented floods. One jökulhlaup in 1934 caused the release of of water over the course of several days. The volcanic lake Grímsvötn was the source of a large jökulhlaup in 1996. There was also a considerable but short-lived eruption of the volcano under these lakes at the beginning of November 2004. On 21 May 2011 a volcanic eruption started in Grímsvötn in Vatnajökull National Park at around 7 p.m. The plume reached up to .