In geological terms Iceland is very young. It was formed less than 20 million years ago from volcanic activity on the floor of the Atlantic Ocean. It is, today, one of the most volcanically active places on Earth. Iceland straddles the Mid-Atlantic Ridge at junction of the American and African plates which are moving apart at a rate of an inch a year. the Ridge runs across iceland from north east to south west and is characterised by a series of craters, hot springs and earthquakes. The ridge averages 30 miles in width and covers some 25% of the country. In the past 10,000 years some 25 of Iceland's volcanoes have been active. On average there is volcanic activity about once every 5 years. Some are small and cause little damage. The most spectacular of recent years was Surtsey eruption on the seabed off the Vestmannaeyjar islands in 1963 when a new island was formed of some 1.7 sq.miles in size. Despite most eruptions being minor there has been catastrophic ones such as that of Lakagígar in the late 18th century which spewed out some 3 cubic miles of lava which is the largest lava flow ever recorded on earth as well as poisonous gases which devastated crops and livestock and about one third of the population perished. In 1973 a new volcano erupted on the island of Heimaey off the south coast and buried one third of the town under lava and ash.

Despite the volcanic activity the island has been shaped by ice. Entirely covered by glaciers during the Ice-Age the mountains have been gouged and the fjords cut by ice. Although the Ice-Age finished some 10,000 years ago it remains a land of ice formed around 500BC and 1500-1900 AD at the coldest periods. Ice covers over 10% of the land. Vatnajökull is over 3000 feet thick and covers some 3000 sq.miles and is not only the largest in Europe but larger than all the others put together. There are instances of Glaciers on top of volcanoes, Snaefelljökull is an example, although it has not erupted for some 700 years. Mount Katla, however, lies under Mýrdalsjökull and is active. When a subglacial volcano erupts it has a more devastating effect than an ordinary one. Hot lava melts the ice causing flash flooding. if Mount Katla erupts it is likely to produce some million gallons of water per second.

There was a volcanic eruption at the end of 1995/early 1996 under Vatnajökull Glacier. The glacier melted causing the level in Grimsvötn to rise higher than the lake could cope with, so it started running under the glacier and finally came out on Skeidarársandur destroying everything in its path. Fortunately it avoided inhabited areas and only destroyed roads and bridges. A new bridge has been constructed and can be seen by clicking here