Eyjafjallajökull is a small volcano (about 40km2) within the chain of volcanoes in the SE Rift Zone. It is the most southerly volcano on mainland Iceland before Surtsey in the sea to the south west. It is a relatively small volcano, and is located W of Katla volcano. Eyjafjallajökull consists of an elongated ice-covered strato volcano with a 2.5-km-wide summit caldera. Fissure-fed lava flows occur on both the E and W flanks of the volcano, but are more prominent on the W side. Although the 1,666-m-high volcano has erupted during historical time, it has been less active than other volcanoes of Iceland's eastern volcanic zone, and relatively few Holocene lava flows are known. The last historical eruption of Eyjafjallajökull prior to an eruption in 2010 produced intermediate-to-silicic tephra from the central caldera during