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Mýrdalsjökull is the southernmost glacier in Iceland and is is the fourth
largest glacier with an area of about 590 km². It covers the upper part
of a large volcano, the Katla caldera. Katla and its caldera is
estimated to have a diameter of about 10 km and the highest point is almost
1500 m.a.s.l. Katla is oval in shape with the longest axis NW-SE and covers an
area 110 km2. The highest points of the ice cap lie on the caldera
rim and include Goðabunga, Háabunga, Austmannsbunga, Enta, Entukollar. Within
the caldera the ice is hundreds of meters thick. Eruptions can start in many
places outside or within the caldera and cause great glacier bursts. Quite a
few glacier snouts flow down onto the lower lying areas and discharge a great
volume of water.
During the summer of 1999 some activity was noted within the
Mýrdalsjökull caldera. On the night of the 18th July came a sudden
flood in the river Jökulsá á Sólheimasandi. The source of the flood
was meltwater from a depression formed simultaneously in the glacier surface,
within the ice drainage basin of Sólheimajökull. After the flood existing
depressions enlarged and crevasses were formed. The depressions became
deeper during the summer and increased in number. The reason was
increased geothermal activity. It is possible that there was a small
eruption at the head of Sólheimajökull that formed a depression and caused the
flood.
Katla erupted very powerfully in 1918 but there are evidence of smaller
eruptions after that. Icelandic volcanologists are expecting another eruption
in next few years so the Myrdalsjokull glacier and the Katla caldera are
monitored quite closely. Just west of Myrdalsjokull glacier is another glacier,
Eyjafjallajokull which is much smaller (50 km²).
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