A Brief Eruptive History
The Past Hundred Years of Katla
Since their settlement in 874 AD, Icelanders have documented events in their country in expert detail. Such documentation depicts volcanic eruptions, earthquakes, snow avalanches, floods, blizzards and other natural events. Because of these detailed records, eruptions by Katla have been well documented. (7) Duration of eruptions range from two weeks to four months. (10)
From the beginning of its documentation, Katla has been recorded as producing 25 km3 magma. Its largest explosive eruption was in 934 AD and is recorded as a VEI 5. Also, Katla’s largest effusive eruption documented was in 934 AD and produced 18 km3 of flood basalt. (5) |
Below: Chart taken from a Computational Geosciences article. (1) *Click to expand*
The last katla eruption to break the ice surface occurred in 1918. This eruption which began October 12, 1918 lasted three weeks and was a basaltic eruption. The height of the eruption plume on that October day was 14km and the maximum volume of the debris-laden jökulhlaup that followed was estimated at 300,000 m3/s and moved at a speed of 10 m/s. The discharge of the glacial outburst floods from this one eruption event was enough to advance the southern coastland by 3-4 km. (however, due to heavy erosion by the sea, this was reduced by 2km within a month). Estimated tephra fallout is 0.7km3 and the volume of transported material is estimated between 0.7 and 1.6km3. (11) Since this large eruption, short lived sub-glacial eruptions in 1955 and 1999 have been debated. No tephra erupted into the atmosphere because the activity was not enough to break through the glacier but both caused moderately sized jökulhlaups and shallow ice cauldrons were seen at the surface of the glacier. (11) |
In April 2010, Katla’s little sister 25 km off her southwest flank erupted. Historically, for the last 1000 years, each time Eyjafjallajökull has erupted, Katla is not long to follow. The linkages between the two volcanoes is not well understood but since June 2011, Katla has been rumbling back to life right on cue. The great volcano has been experiencing many tens to hundreds of small earthquakes daily for the past year. Katla is known to be seismically active, although seasonal fluctuations have been attributed to her ice cap melting during the summer and the resulting reduction of pressure on the magma chamber. Though the increase in seismic activity is not a direct indicator of an impending eruption, the last major eruption was 95 years ago so the volcano is being carefully watched. (10)
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