Iceland's volcanic eruption as well as the towering column of ash spewing out of it have both declined significantly, an Icelandic seismologist said Monday.
"Currently the eruption has diminished markedly," Bryndis Brandsdottir of the University of Iceland told AFP, basing her comment on seismological radar readings in Reykjavik.
"The ash column does not rise above 3,000 metres (9,800 feet)," or less than half its original height, she added.
Icelandic geophysicist and civil protection advisor Magnus Tumi Gudmundsson agreed that the ash column from the Eyjafjallajokull eruption -- which has paralysed air travel in most of Europe -- was decreasing, five days after it began.
"Less ash has been generated over the last 36 hours than previously. The ash production has been reduced," he told AFP.
Brandsdottir said the eruption started decreasing Sunday afternoon, but that is had been difficult at the time to monitor the volcano "because of weather and clouds."
"The amount of tethra (a type of ash that makes up the volcano plume) has diminished to the point that (experts monitoring the eruption) could not see the column, indicating it did not rise above 3,000 metres," she said.
Seismological radars in Reykjavik had also picked up additional tremors near the Eyjafjallajokull volcano that began erupting for the second time in less than a month last Wednesday, Brandsdottir said.
But she stressed seismometers not only measured volcanic tremors but also recorded exterior seismic factors such as strong winds and tremors produced by the ocean.
"The North Atlantic ocean can also produce tremors. The increase in tremors overnight yesterday is partly associated with the strong northerly winds," blowing ash to the south, she said.
But these strong, northerly winds would have no effect on the transport of ash to Europe, Brandsdottir said, pointing out that an ash column below 3,000 metres "is hardly transported far away."
Explore further: A 3-D view of the Greenland Ice Sheet opens window on ice history