“I read that the Bárdarbunga volcano in Iceland is considered restless, what does this mean?
Well, it simply means that it is showing some signs that it might be moving towards a future eruption. In the case of Bárdarbunga we are talking about earthquakes that are deep enough to be of magmatic origin, we also see GPS motion indicating that magma could be moving into the system, and on occasion we see magmatic tremor. For these reasons it has been called “restless”. The reason why Bárdarbunga is not classified as Active is that we do not really know how she behaves before an eruption. This is because the last eruption started in December 1902 and ended in June 1903…” Bardarbunga Info & More