|Thorolfsfell, a tuya in southern Iceland. (Click on the image to view it full-size.)|
Iceland represents a subaerial portion of the mid-Atlantic Ridge, and its Neovolcanic zone is one of the most volcanically active regions on Earth. It is subjected to frequent eruptions, and has experienced some of the largest historic eruptions anywhere (e.g. the 1783-1784 Laki basaltic fissure eruption). During the Pleistocene, most of the island was covered by a 1 km thick ice sheet (Saemundsson, 1980). Approximately 11% of Iceland's surface is still covered with ice. Consequently, Iceland has numerous glaciovolcanic features, including tuyas, hyaloclastite ridges, and pillow sheets. Basaltic compositions dominate and have been studied most thoroughly, but extensive recent research has been conducted, and is ongoing, on Iceland's rhyolitic subglacial volcanoes .
Iceland has experienced subglacial volcanic eruptions throughout its recorded history. These are commonly associated with jökulhlaups, catastrophic outburst floods associated with subglacial eruptions which leave behind massive outwash plains called sandurs. Historically, many jökulhlaups have been reported even though the eruptions that generated them were not actually witnessed. For example, the volcano Katla has produced at least seven jökulhlaups since 1625 A.D., which have formed the Mýrdalssandur, on Iceland's southern coast. More recently, subglacial volcanic eruptions were witnessed and studied in 1996 (the Gjálp eruption) and 1998.
Click on the thumbnail images below to view full-size images of some Icelandic volcanoes.
Images of rhyolitic subglacial volcanoes were provided by Hugh Tuffen, Lancaster University.
|The volcano Eyjafjöll, in southern Iceland.||Columnar-jointed rhyolite lava flow at Bláhnúkur, Torfajökull, Iceland.|
|Overview of the subglacial rhyolite volcano Bláhnúkur, Torfajökull, Iceland.||Northeastern Rauðufossafjöll, Torfajökull, Iceland, a rhyolite tuya.|
|Southeastern Rauðufossafjöll a rhyolite tuya at Torfajökull, Iceland.||Rhyolite tuyas at Torfajökull, Iceland.|