Iceland formed (and continues to form) from volcanism along the mid Atlantic Ridge and first emerged from the sea about 16 million years ago. The forces that led to the creation of this volcanic island remain active today and are concentrated along a swath from southwestern to northeastern Iceland; a secondary branch of the underlying oceanic ridge extends from the middle of this corridor to the central portion of Iceland's southern coast.
Along these geothermal corridors, tectonic forces are pushing the North American and Eurasian plates apart (northwestern Iceland lies on the North American Plate while the southeastern half of the country lies on the Eurasian Plate); in concert, the intervening crust thins and magma wells near the surface, transferring heat to the ground water and producing the classic geothermal features of hot springs, geysers and mudpots. At times, the magma breaks through to the surface, leading to vast flows of basalt while, under other conditions, pressure in the magma chamber builds and is eventually released in a violent volcanic explosion.
As one might expect, most of Iceland's active volcanoes and geothermal features lie within or near these corridors; the volcanic eruption in March of 2010 was associated with the secondary ridge. As the island continues to grow, older volcanoes move further from these ridge lines and eventually lose their connection with the magma chambers; when this occurs, the volcano becomes extinct. On the other hand, many of Iceland's inactive volcanoes retain the potential for eruption and all regions of the island remain at risk for the direct or indirect effects of volcanic events. Until such time that ocean floor spreading ceases in the North Atlantic, volcanism will rule the magnificent landscape of Iceland.
