Hekla

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Hekla

July 2005: Hekla beyond a field of volcanic ash
Elevation 1,488 metres (4,882 ft)
Location Iceland
Coordinates 63°59′N 19°42′W / 63.983, -19.7Coordinates: 63°59′N 19°42′W / 63.983, -19.7
Type Stratovolcano
Last eruption February 28, 2000

Hekla is a stratovolcano located in the south of Iceland at 63.98° N 19.70° W, with a height of 1,488 m (4,882 ft). Hekla is Iceland's most active volcano; over 20 outbreaks have occurred in and around the volcano since 874. During the Middle Ages, Icelanders called the volcano the "Gateway to Hell."

Hekla is part of a volcanic ridge, 40 km (25 mi) long. However, the most active part of this ridge, about 5.5 km (3.4 mi) long, is considered to be the volcano Hekla proper. Hekla looks rather like an overturned boat, with its keel being in fact a series of craters, two of which are generally the most active.

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[edit] Famous eruptions

The earliest recorded eruption of Hekla took place in 1104, although very likely there had been many more during the time of Viking settlement. The 1104 eruption was one of Hekla's largest known, ejecting 2.5 cubic km of tephra.

Since then there have been between twenty and thirty considerable eruptions, with the mountain sometimes remaining active for periods of six years with little pause. Hekla took a long rest of more than sixty years duration prior to 1845, when it suddenly burst forth on September 2 (Anonymous, 1872):

After a violent storm on the night of the 2nd of September in that year, the surface of the ground in the Orkney Islands was found strown with volcanic dust. There was thus conveyed to the inhabitants of Great Britain an intimation that Hecla [sic] had been again at work. Accordingly, tidings soon after arrived of a great eruption of the mountain. On the night of the 1st of September, the dwellers in its neighbourhood were terrified by a fearful underground groaning, which continued till mid-day on the 2nd. Then, with a tremendous crash, there were formed in the sides of the cone two large openings, whence there gushed torrents of lava, which flowed down two gorges on the flanks of the mountain. The whole summit was enveloped in clouds of vapour and volcanic dust. The neighbouring rivers became so hot as to kill the fish, and the sheep fled in terror from the adjoining heaths, some being burnt before they could escape.
On the night of the 15th of September, two new openings were formed — one on the eastern, and the other on the southern slope — from both of which lava was discharged for twenty-two hours. It flowed to a distance of upwards of twenty miles, killing many cattle and destroying a large tract of pasturage. Twelve miles from the crater, the lava-stream was between forty and fifty feet deep and nearly a mile in width. On the 12th of October a fresh torrent of lava burst forth, and heaped up another similar mass. The mountain continued in a state of activity up to April 1846; then it rested for a while, and began again in the following month of October. Since then, however, it has enjoyed repose.
The effects of these eruptions were disastrous. The whole island was strewn with volcanic ash, which, where they did not smother the grass outright, gave it a poisonous taint. The cattle that ate of it were attacked by a murrain, of which great numbers died. <This has since been attributed to fluoride poisoning caused by presence of large quantities of hydrogen fluoride in the ash.> The ice and snow, which had gathered about the mountain for a long period of time, were wholly melted by the heat. Masses of pumice weighing nearly half a ton were thrown to a distance of between four and five miles.

Eruptions in Hekla are extremely varied and difficult to predict. Some are very short (a week to ten days) whereas others can stretch into months and years (the 1947 eruption started March 29, 1947 and ended April 1948). But there is a general correlation: the longer Hekla goes dormant, the larger and more catastrophic its opening eruption will be (Þórarinsson, 1967).

Mount Hekla erupting in 1980. Seen from 4 km NE of the summit.
Mount Hekla erupting in 1980. Seen from 4 km NE of the summit.

The most recent eruption was on February 26, 2000. During this eruption, a NASA DC-8 aeroplane accidentally flew through the plume with all instruments switched on, resulting in unprecedented measurement of a young volcanic plume. The next eruption is believed by locals to be due some time in mid to late 2008.

Report on this last eruption in January 2003: Up until now, it has always been assumed that Hekla was incapable of producing the most dangerous of volcanic phenomena, the pyroclastic flow. Now, however, a team from the Norvol Institute in Reykjavík, under the leadership of Dr. Ármann Höskuldsson, has reported that they have found traces of a pyroclastic flow, roughly 5 km long, stretching down the side of the mountain. This will call for a reappraisal of volcanic eruptions of the basic rock type, which up to now were generally thought not to produce large pyroclastic flows. It will also require that the public and curious spectators who always rush to the scene at the start of a new outbreak, to be kept much further away from the volcanic activity than was thought necessary during previous outbreaks.

Mount Hekla seen from the Þjórsárdalur
Mount Hekla seen from the Þjórsárdalur

[edit] Historical and prehistoric eruptions

This volcano erupted in 2000, 1991, 1981, 1980, 1970, 1947, 1845, 1766, 1693, 1636, 1597, 1510, 1434, 1389, 1341, 1300, 1222, 1206, 1158 and 1104.

One of the largest Holocene eruptions was the Hekla 3 eruption of 1159 BC, which threw about 7.3 cubic km[1] of volcanic rock into the atmosphere and very likely caused cooling of global temperatures for a few years afterwards. Traces of this eruption have been identified in Scottish peat bogs, and in Ireland a study of tree rings dating from this period has shown negligible tree ring growth for a decade. [2]

Main eruptions in prehistoric times:

  • Hekla 5: 6800 BP
  • Hekla 4: 4260 BP
  • Hekla Sv: 3720 BP
  • Hekla 3: 2950 BP (1159 BC)

[edit] Miscellaneous

  • Hekla, Op 52 (1964) by Icelandic composer Jón Leifs is sometimes called the "loudest classical music of all time". The requirements for a performance of Hekla include four sets of rocks hit with hammers, steel plates, anvils, sirens, cannons, metal chains, choir, a large orchestra, and organ.[3]
  • In 2006, Australian world/fusion band Umanee recorded and published instrumental song titled Mount Hekla performed by drums, cello and hurdy-gurdy.
  • Hecla was the name of a Carmarthen and Cardigan Railway steam locomotive built in 1864.
  • In the Boston area, Hekla pastries can be found - large, upside-down cinnamon rolls with white sugar icing spooned over the top to look like the snow-topped volcano.
  • The poet William Blake shows Winter being banished to Hecla in To Winter, one of the works from his Poetical Sketches.

[edit] See also

[edit] References

[edit] Notes

  1. ^ Smithsonian Institution Global Volcanism Program: Hekla
  2. ^ Cunliffe, Barry (2005). Iron Age Communities in Britain. Routledge, 256. ISBN 0415347793. Pg 68
  3. ^ Booklet of CD: "Earquake" (sic), Helsinki Philharmonic Orchestra, Leif Segerstam. Ondine ODE 894-2

[edit] External links