Vatnajökull, the largest glacier of Iceland is situated in the south eastern region of this Icelandic country and stretches over 8,100 km² and counted as the largest glacier of European continent by volume that is 3,100 km³. It is categorized under ice cap glacier in central Iceland and like many glaciers of Iceland; it has a number of active and dormant volcanoes under it. Once such active volcano situated under the lake of Vatnajökull is Grímsvötn.

If you plan to travel to the extreme south eastern region of the Iceland, you will get the opportunity to discern the far-fetched view of the Grimsvotn volcano whose subsequent eruption caused flood in the region.

Grimsvötn volcano under Vatnajökull ice cap is one of the two major volcanic centers that is sited below the ice. The other one is the Bardarbunga volcano but the Grimsvötn volcano is considered to be more active than its counterpart.
Under Vatnajökull glacier, in the last ice age several volcanic eruptions took place and created a number of sub-glacial eruptions. These sub-glacial eruptions created Tuyas namely Herðubreið that was the part of Vatnajökull in reality.

Eruptions at Grimsvotn Volcano can be classified as phreatomagmatic eruptions that are caused due to the contact of water with magma. Such eruptions caused large glacial lake that burst in the form of flood in the future. The most recent flood due to eruption at Grímsvötn volcano occurred in May 2011. The volcanoes usually cause a substantial yet bout eruption and this time was noted to send a plume of 50,000 ft height making it the largest eruption that ever happened in Iceland after 1947. The previous incident of such eruption arose at Grimsvotn volcano in 2010, 2004, 1998 and 1996 and even before that.