Katla is a large, active Iceland volcano situated in southern part. It is known to be very dangerous. From 930 to 1918, record shows that it has erupted 20 times of a 13–95 year interval. For 96 years no violent activity of eruptions have been recorded, but records of tiny blasts were noted that did not tend to break any ice cover, including the years 1955 and 1999.
On October 12, 1918, the last known eruption of Katla began and ended after 24 days, measured likely as VEI-5 magnitude level of volcano eruption. Its present silence and inactivity is noted as the longest in history.
Recently, seismicity and bulging of Katla has been seen to increase in measurement, thus close monitoring was undertaken statistically to prevent an uncontrollable surprise eruption.
Since 1999, Katla has depicted signals of unrest, and as geologists indicate it might signify eruption in the near future. Intensified monitoring was implemented after the March 2010 eruption.
Movement of tremor was again identified in June 2011 at Katla Iceland volcano. Days after, a swarm of earthquakes in the caldera took place, magnifying magma activity within the volcano, giving cause for increased worry of a possible eruption.
On July 8 and 9, 2011, a pierce in harmonic tremors was again measured, as an eruption of small intensity took place at Katla. Cauldron and cracks on the Glacier was formed. Few sub glacial eruptions might have started as media in Iceland reported.
In the river of Múlakvísl on the morning of July 9 reports of glacier flood were aired and at Skálm River as well. It caused a bridge along Múlakvísl to be devastated including some areas of the road.