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Surtsey

From Academic Kids

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The island of Surtsey in 1999

Surtsey (Icelandic: Surtur's island) is a volcanic island off the southern coast of Iceland. At 63°17'N, it is also the southermost point of Iceland. It was formed in an undersea eruption which began 130 metres below sea level, and reached the surface on November 14, 1963. The eruption may have started a few days earlier, and lasted until June 5, 1967, when the island reached its maximum size of 2.7 km˛. Since then, wind and wave erosion has seen the island steadily diminish in size: as of 2005 it is only 1.4 km˛ in size.

The new island was intensively studied by volcanologists during its creation, and since the end of the eruption has been of great interest to botanists and biologists as life has gradually colonised the originally barren island.

The undersea vents that produced Surtsey are part of the Vestmannaeyjar ("West Man Islands") submarine volcanic system, part of the fissure of the sea floor called the Mid-Atlantic Ridge. Vestmannaeyjar also produced the famous eruption of Eldfell on the island of Heimaey in 1973.

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Contents

Precursors to the eruption

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Surtsey, three days after the onset of the eruption

At 07:15 UTC+0 on November 14, 1963, the cook of Ísleifur II, a trawler sailing off the Vestmannaeyjar archipelago south of Iceland spotted something south-west of the boat, which turned out to be a rising column of dark smoke. The vessel went to investigate the smoke, the captain thinking it might be a boat on fire, but instead they encountered explosive eruptions giving black columns of ash, indicating that a volcanic eruption had begun beneath the sea.

Although the eruption was unexpected, there had been some indications before it began that volcanic activity was imminent. A week beforehand, a seismograph in Reykjavík recorded weak tremors, but their location was not determined. Two days before the eruption began, a marine research vessel noted that the sea in the area was somewhat warmer than normal, and at the same time, people in the coastal town of Vík on the mainland 80km away had noticed a smell of hydrogen sulphide.

It is likely that the eruption had begun some days before November 14th. The sea floor is 130m below sea level, and at this depth explosive eruptions would be quenched by the water pressure. As the eruption built up a volcano approaching sea level, the explosions could no longer be quenched, and the eruption broke the surface.

Early days

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Surtsey's ash column rises over the newly forming island

By 11:00 on November 14, 1963 the eruption column had reached several kilometres in height. At first the eruptions took place at three separate vents along a northeast-southwest trending fissure, but by the afternoon the separate eruption columns had merged into one along the erupting fissure. Over the next week, explosions were continuous, and after just a few days the new island, formed mainly of scoria, measured over 500 metres in length, and had reached a height of 45 metres. The new island was named after the fire giant Surtur from Norse mythology. As the eruptions continued, they became concentrated at one vent along the fissure, and began to build the island into a more circular shape. By November 24, the island measured about 900x650m. The violent explosions caused by the meeting of lava and sea water meant that the island consisted of a loose pile of volcanic rock (scoria), which was eroded rapidly by north Atlantic storms during the winter. However, eruptions more than kept pace with wave erosion, and by February 1964, the island had a maximum diameter of over 1300m.

French landing

One interesting event early in the island's life was the landing of three French journalists representing the magazine Paris Match on December 6, 1963. They stayed for about 15 minutes before violent explosions encouraged them to leave. The journalists jokingly claimed French sovereignty over the island, but Iceland quickly asserted that the new island belonged to it, having appeared in Icelandic territorial waters.

Ferdinandea, near Sicily, is another island created by volcanic eruptions which has been subject to disputes over sovereignty.

A permanent island

The explosive eruptions caused by the easy access of water to the erupting vents threw rocks up to a kilometre away from the island, and sent ash clouds as high as 10km up into the atmosphere. In early 1964, though, the eruptions had built the island to such a size that sea water could no longer easily reach the vents, and the eruptions became much less explosive. Instead, lava fountains and flows became the main form of activity. These resulted in a hard cap of extremely erosion-resistant rock being laid down on the loose volcanic pile, which prevented the island being washed away rapidly. Effusive eruptions continued until 1965, by which time the island had a surface area of 2.5km˛.

The eruption gradually dies down

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The eruption vents today

In 1965 the activity on the main island diminished, but outlying vents on the fissure saw eruptions which built small islands to the north and south of Surtsey, called Jolnir and Syrtlingur. However, these were rapidly eroded away. A third vent called Surtla built a submarine mountain (seamount) which never reached sea level. 1966 saw the return of effusive eruptions on the island, giving it further resistance to erosion. The eruption rate was diminishing steadily throughout this time, and on June 5th 1967, the eruption ceased, and the volcano has been dormant ever since. The total volume of lava emitted during the three and a half year eruption was about one cubic kilometre, and the island's highest point was 174m above sea level.

Since the end of the eruption, erosion has seen the island diminish in size. A large area on the southeast side has been eroded away completely, while a sand spit called Norðurtangi (north point) has grown on the north side of the island. It is estimated that about 0.024km³ of material has been lost due to erosion - this represents about a quarter of the original volume of the island.

The settlement of life

A classic site for the study of biocolonization from founder populations that arrive from outside ('allochthonous'), Surtsey was declared a nature reserve in 1965, while the eruption was still in active progress. Today only a small number of scientists are permitted to land on Surtsey; the only way anyone else can see it closely is with a small plane.

Plant life

Life settled slowly on the island. The first life to appear was moss and lichen, which began to appear on the island as early as 1965. Mosses and lichens now cover much of the island. During the island's first twenty years, 20 species of plants were observed at one time or another, but only 10 became established in the nutrient-poor sandy soil.

As birds began nesting on the island, soil conditions improved, and more advanced species of plants were able to survive. In 1998, the first bush was found on the island - a Salix phylicifolia bush, which can grow to heights of up to 4 metres.

In total at least 60 species of plant have been found on Surtsey, of which about 30 have become established. More species continue to arrive, at a typical rate of roughly 2-5 new species per year.

Birds

The expansion of bird life on the island has both relied on and helped to advance the spread of plant life. Birds use plants for nesting material, but also assist in the spreading of seeds, and fertilise the soil. Birds began nesting on Surtsey three years after the eruptions ended, with fulmar and guillemot the first species to set up home. Eight species are now regularly found on the island.

A seagull colony has been present since 1986, although gulls were seen briefly on the shores of the new island only weeks after it first appeared. The gull colony has been particularly important in developing the plant life on Surtsey, as gulls have much more of an impact on plant colonization than other breeding species.

An expedition in 2004 found the first evidence of Atlantic Puffins nesting on the island. Puffins are extremely common in the rest of the archipelago.

Marine life

Seals began breeding on the island in 1983, and both common and grey seals are seen on the island. Killer whales are frequently seen in the waters around the island.

On the submarine portion of the island, many aquatic species are found. The rocks are covered in algae, and starfish are abundant.

The future for Surtsey

The typical pattern of volcanism in the Vestmannaeyjar archipelago is for each eruption site to see just a single eruption, and so the island is unlikely to be enlarged in the future by further eruptions. The heavy seas around the island have been eroding it ever since the island appeared, and since the end of the eruption almost half its original area has been lost. However, the island is unlikely to disappear entirely in the near future. The eroded area consisted mostly of loose tephra, easily washed away by wind and waves. Most of the remaining area is capped by hard lava flows, which are much more resistant to erosion. While the island will undoubtedly get smaller yet, it will nonetheless probably persist for many centuries before being eroded away completely.

See also

References

  • R. Decker and B. Decker, Volcanoes, (1989) includes a narrative of Surtsey's birth.
  • National Geographic article Surtsey: Island Born of Fire (1965) contains much useful information on the birth of Surtsey and illustrated description of the stages of its production up to 1965.
  • For volcanologists, see either S. Thorarinsson et al. (1964) "The submarine eruption off the Westmann Islands 1963-64". Bull Volcanol 27:435-445 (a short account of the famous eruption) or S. Thorarinsson (1967) "Surtsey - The new island in the North Atlantic". Viking Press, New York, pp 1-47 (a more complete account of the eruption with numerous photographs of tephra jets)

External Links

is:Surtsey nl:Surtsey pl:Surtsey sv:Surtsey

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