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NASA satellite image: The wave clouds have a hot origin
Photo: NASA
When a wide band of clouds moved over Iceland at the end of April, everything seemed inconspicuous at first.
But noticeable waves formed in a certain region.
Such formations make disturbances in the atmosphere visible.
These do not occur very rarely, for example when air masses push themselves over obstacles such as mountain ridges or icebergs.
But a topographical explanation was out of the question in this case, say scientists.
So how did they come about then?
The NASA satellite "Landsat 8" recorded the clouds at noon on April 30th.
That same night, the satellite photographed the area again, this time in the infrared light range.
The clearly red glowing region shows the volcano Fagradalsfjall.
At the fire mountain
The shield volcano on the Reykjanes peninsula, about 40 kilometers from Iceland's capital Reykjavík, did not erupt in an explosive manner, but has been spewing hot lava since the end of March.
At the end of April, the fountains reached several hundred meters into the air.
The resulting heat apparently formed the wave clouds.
"The difference in density between the air heated by the volcano and the environment is very likely responsible for the turbulence," said Jean-Paul Varnier, atmospheric researcher at NASA.
Throstur Thorsteinsson, a scientist at the University of Iceland, also believes the wave clouds were likely affected by the eruption.
He had noticed in early May that the volcano's activity increased even further and began to pulsate.
Long periods of rest alternated with short phases in which lava fountains shot up.
The start and stop of these fiery convulsions likely created the unique pattern in the atmosphere, Thorsteinsson said.
The volcano is still active, but the lava has not risen as high recently.
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The outbreak had attracted numerous onlookers
Photo: JEREMIE RICHARD / AFP
At the beginning of April, two new crevices opened up on the volcano.
The police had to evacuate the affected area and onlookers had to be brought to safety in helicopters.
The lava comes from an underground volcanic system called Krýsuvík, which had previously been inactive for 900 years.
The outbreak was announced by thousands of earthquakes.
According to the authorities, there has so far been no danger to people, localities or the not far away capital Reykjavík.
Iceland has 32 active volcanic systems and an eruption occurs on average every five years.
In April 2010, the eruption of the smaller volcano Eyjafjallajökull paralyzed air traffic in Europe for a month.
More than 100,000 flights were canceled at the time, and a good ten million travelers were stuck at airports, some of them for days.
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