Thomas Walter is geologist and volkanologist at the German Research Center for Geosciences in PotsdamIngolf Baur: How high is the risk that neighboring volcanoes will also erupt on Iceland? Thomas Walter: Yes, indeed - we know that the last two historic eruptions at Eyjafjallajökull were followed by an eruption at Katla vulcano. Katla vulcano is often considered to be the big brother of Eyjafjallajökull.   So, that is a simple rule? What’s the underlying mechanism? No, statistically the number is two and a statistic is not allowed here. But the observation was in two eruptions - it was in the 16th century and again in the 18th century, Katla erupted shortly after Eyjafjallajökull. And this was also the concern of scientists in the past - but, at present, Katla is quiet and there is no concern about... Ok - let's hope it will stay that way. Now, what about Eyjafjallajökull? Will the volcano really cool down as it seems at the moment? It's calming down. Whether it will really stop to erupt, that's very difficult to say at the moment. We know that the eruption rate has reduced in the past days - it's about a tenth of what we have seen last week. Were you actually surprised by the fact of an erupting Eyjafjallajökull? Not really, because we know in the scientific literature also it was discussed that Eyjafjallajökull prepared for an eruption - over the last thirty years. It was observed that the vulcano was inflating. The ground was deforming. We have seen lots of seismic activity early this year and so the vulcano was getting ready to erupt. But you couldn't really tell what the time then would be for the vulcano to erupt? It was observed that shortly before the eruption on 20th May, 20th March this year - that seismicity sharply increased and that's also the reason why the local authority issued a warning to the local population. How many days before the eruption was that? I cannot tell the details but this was one of ...