In Iceland people wait for the possible eruption of Bárðarbunga volcano with a strange combination of excitement and anxiety. The earthquakes continued through Wednesday night and into Thursday morning, but there is still no sign of magma making its way to the surface. Scientists are cautious because nobody wants to be the one who falsely predicted an eruption, but even so they seem to be leaning towards the opinion that probably the old volcano is waking up.
The eruption would be under a glacier between 150 and 600 meters thick. That means the ice would melt and Jökulsá á Fjöllum, a glacial river, would flood. The river might increase 10 to 40-fold. After the start of an eruption the water would take about an hour to reach the border of the glacier. It would be at Herðubreiðarlindir in four and a half hours, at the bridge by Grímsstaðir in seven hours and down to Ásbyrgi, a natural pearl, in about nine hours. The area can be seen on this map.
Because nobody knows how big the flood might be, estimates of possible damage range widely. The three bridges over Jökulsá might all be washed away. In case of an extreme flood, in which the flow of water might increase 100-fold, there might be great damage to nature. Many of the natural pearls around Jökulsá are thought to be formed in such floods. Among the areas that might be affected are Herðubreiðarlindir, Hljóðaklettar, Dettifoss and Ásbyrgi. Such a flood is not considered likely at the moment.
Jökulsá has not been flooded for about 300 years but there are recorded floods that caused great damage in the 15th, 17th, and 18th centuries. The areas in Kelduhverfi and Öxarfjörður were both flooded and people are said to have been saved by climbing to the roofs of their houses.
The eruption itself would send out tons of ashes, possibly having an effect on air traffic, although most anticipate that the effect would be smaller than in the Eyjafjallajökull eruption in 2010.