QA on the eruption in Eyjafjallajökull 2010
Will other volcanoes erupt?
There are currently no indications that other volcanoes nearby, such as Katla or Hekla, are on the verge of erupting.
Is the eruption ongoing?
It is not possible to predict the duration of the eruption. Previous known eruptions from this volcano were in the years 1612 and 1821-3, when it erupted on and off for over a year. Little or no volcanic activity has been observed since 23rd May but scientists have not yet declared that the eruption is over.
What kind of an eruption is it?
The eruption is an explosive eruption beneath a glacier. The ash is fluorine rich, of intermediate silica content and the particles are very fine.
Is the ash dangerous?
Yes, the fluorine is dangerous to livestock. The fine ash can also effect human health, for example the respiratory system. The fluorine content is approximately 850 mg/kg according to chemical analysis carried out by the Institute of Earth Sciences, University of Iceland, on a sample taken 19 April. An earlier sample since 14 April only measured 25-35 mg/kg of fluorine because the water vapour from melting ice rinsed the ash. When the eruption progressed, water became less accessible.
Has ash fallen in Iceland?
Yes, in the southeast and extreme south of the country (downwind). Wind has been quite strong, so dry ash that fell earlier has, at times, been blowing with the wind causing local reduction of visibility.
How fine is the ash?
One sample taken by the Environment Agency on Mýrdalssandur (50 km away from the eruption site) after the ashfall 14-16 April was analysed by Institute of Earth Sciences and is very fine grained:
24% of the sample is under 10 μm (as aerosol)
33% of the sample is in the range of 10-50 μm
20% of the sample is in the range of 50-146 μm
23% of the sample is in the range of 146-294 μm
How high is the ash plume?
The greatest height that the plume has reached is 33,000 ft (about 11 km) on the first eruption day. Early morning 18.04.2010 the plume disappeared from IMO's radar. On average, it is probably under 10,000 feet (3 km), approximately.
How far has the ash plume reached?
The plume has been detected over the British Isles and further east, in Norway and in Finland. The Icelandic Meteorological Office issues daily forecasts of ashfall. WMO issued a briefing (20 April) of frequently asked questions regarding the eruption and the ash plume (pdf 1,5 Mb).
Why were there floods? Can floods always be expected?
Several very sudden jökulhlaups (glacier outburst floods) have occurred during the subglacial eruption in Eyjafjallajökull volcano. The largest one came in the very beginning of the event with maximum discharge about 2000-3000 m3/sec. Now the eruption is constrained to one vent and, therefore, very limited amount of ice is melted and, accordingly, little danger of large jökulhlaups. The floods are monitored by online gauges in several rivers around the volcanoes Katla and Eyjafjallajökull. Large or damaging jökulhlaups are not expected in connection to this event unless changes occur in the eruption pattern.
How is the eruption monitored?
The Icelandic Meteorological Office monitors earth movements, water conditions and weather and issues warnings. Many kinds of measurements are carried out by the IMO and other agencies that provide valuable information used to warn of impending danger, for example potential eruptions and floods. The IMO's weather radar on the southwest tip of the country shows the height of the ash plume, which is important for calculating the distribution of the ash. There is a 24/7 watch at the IMO, where a meteorologist is present and a seismologist and hydrologist are on call. The IMO works closely with the National Emergency Agency, the University of Iceland and the British Meteorological Office, where the London VAAC (Volcanic Ash Advisory Centre) is stationed. The London office gives information on ash which are based on information from the Icelandic Met Office.
How are eruptions forecast and monitored in Iceland?
To forecast and monitor seismic and volcanic activity in Iceland, IMO operates a nationwide digital network of seismic stations and continuous GPS stations. Subglacial eruptions often co-incide with jökulhlaups. To monitor the jökulhlaups, IMO uses water-level gauges and electrical conductivity meters. More about this in an article in Eos.
How do I find weather forecasts for Iceland?
Information on the weather conditions near the volcano can be viewed on the weather pages of the IMO-web and navigated from there; for the areas near Eyjafjallajökull choose South or Southeast. The text forecast is most reliable but maps with specific wind-, temperature- and precipitation forecasts are automatic. There are no highland stations near the volcano. The difference between the weather in the lowland and in the mountains can be considerable. Wind-chill and wetness (rain, snow or blowing snow) are always a potential hazard, as sudden weather changes are more common on higher ground than in the lowland.
How do I find information on present weather in Iceland?
For the present weather one can view the newest synoptic analysis with observations plotted according to WMO standards. Latest observations on various stations are available; for the areas near Eyjafjallajökull choose South or Southeast. There are no highland stations near the volcano. The difference between the weather in the lowland and in the mountains can be considerable. Wind-chill and wetness (rain, snow or blowing snow) are always a potential hazard, as sudden weather changes are more common on higher ground than in the lowland.
