Eyjafjallajokull is one of Iceland's smaller ice caps located in the far south of the island. The ice cap covers the caldera of a volcano 1666 m in height. The volcano had been dormant for 200 years
Cause of eruption
Iceland lies on the Mid Atlantic Ridge, a constructive plate boundary between the North American plate and Eurasian plate. Iceland lies on the Mid Atlantic Ridge, a constructive plate boundary between the North Atlantic Ridge and Eurasian plates. This is where, as the plates move apart, new material (magma) rises from the earth’s mantle below to create new rock at its spreading edges. This plate boundary is further complicated by the fact that Iceland is also thought to be located over a hot spot so that there is more magma production and volcanic activity than might otherwise be expected in this location (a hot spot is where the earth’s crust is thinner and it easier for magma to upwell in the region).
First eruption phase
The volcanic events starting in March 2010 are considered to be a single eruption divided into different phases. Initially a fissure opened up, about 150 m in length running in a northeast to southwest direction, with 10 to 12 erupting lava craters ejecting lava at a temperature of about 1000 °C up to 150 m into the air. The lava was basalt and relatively viscous, causing the lava stream to be slow. The molten lava eventually flowed more than 4 000 m to the northeast of the fissure. Ash ejection from this phase of the eruption was small, rising to no more than 4 km into the atmosphere. The Lava fountains were a tourist attraction in March & it led to a short term rise in tourism
Second eruption phase
On 14 April 2010, the eruption entered an explosive phase and ejected fine, glass-rich ash to over 8 km into the atmosphere, which was then deflected to the east by westerly winds. The second phase is estimated to have been a volcanic explosive index (VEI) 4 eruption, which is large, but not nearly the most powerful eruption in VEI terms.
The volcano is in a remote corner of Iceland. The local, dispersed farming community is home to few people. There were minor local impacts:
• A thick layer of ash fell on farm pastures at Raufarfell. This has become wet and compact, making it very difficult to continue farming, harvesting or grazing livestock.
• Locally, river levels rose as part of the ice cap melted.
• Some local gravel roads were blocked by falling ash.
However, what made this volcanic activity so hazardous was the fact that the ash became disruptive to air travel. This was due to a combination of the following four factors:
1. The volcano's location is directly under the polar jet stream.
2. The explosive power of the eruption meant that the ash went up high (5 miles high – to the tropopause where planes fly) into the jet stream & because it was so fine, it travelled long distances
3. Anticyclonic conditions over the UK & the direction of the jet stream meant ash was blown from NW to SE across Europe
4. The second eruptive phase took place under 200 m of glacial ice. The resulting meltwater flowed back into the erupting volcano which created a phreatic eruption with two specific phenomena:
The rapidly vaporizing water significantly increased the eruption's explosive power.
The erupting lava cooled very rapidly, which created a cloud of highly abrasive, glass-rich ash which could damage jet engines.
Iceland has 2 to 3 eruptions every years so has excellent hazard management. Eyjafjallajokull was monitored by the Reykjavik Institute monitored the volcano. Seismometers had shown evidence of volcanic activity – there were s shallow earthquakes swarms in the 5 months preceding the eruption. Data from GPS (global positioning satellites) showed ground deformation in Feb 2010 – the ground had risen by 8cm;