It was formed in a volcanic eruption which began below sea level, and reached the surface on 14 November 1963.
On 13 November, a fishing vessel in search of herring, equipped with sensitive thermometers, noted sea temperatures SW of the eruption center were higher than surrounding waters. ====Eruption at the surface==== At 07:15 UTC on 14 November 1963, the cook of Ísleifur II, a trawler sailing these same waters, spotted a rising column of dark smoke southwest of the boat.
Three French journalists representing the magazine Paris Match notably landed there on 6 December 1963, staying for about 15 minutes before violent explosions encouraged them to leave.
Effusive eruptions continued until 1965, by which time the island had a surface area of . On 28 December 1963, submarine activity to the northeast of Surtsey began, causing the formation of a ridge high on the sea floor.
However, eruptions more than kept pace with wave erosion, and by February 1964, the island had a maximum diameter of over . The explosive phreatomagmatic eruptions caused by the easy access of water to the erupting vents threw rocks up to a kilometre (0.6 mi) away from the island, and sent ash clouds as high as up into the atmosphere.
The journalists jokingly claimed French sovereignty over the island, but Iceland quickly asserted that the new island belonged to it. ====Permanent island==== By early 1964, though, the continuing eruptions had built the island to such a size that sea water could no longer easily reach the vents, and the volcanic activity became much less explosive.
Eruptions at Surtla ended on 6 January 1964, and it has since been eroded from its minimum depth of below sea level. ====Subsequent volcanic activity==== In 1965, the activity on the main island diminished, but at the end of May that year an eruption began at a vent off the northern shore.
The rocks are covered in algae, and seaweed covers much of the submarine slopes of the volcano, with its densest cover between below sea level. ====Other life==== Insects arrived on Surtsey soon after its formation, and were first detected in 1964.
Effusive eruptions continued until 1965, by which time the island had a surface area of . On 28 December 1963, submarine activity to the northeast of Surtsey began, causing the formation of a ridge high on the sea floor.
Eruptions at Surtla ended on 6 January 1964, and it has since been eroded from its minimum depth of below sea level. ====Subsequent volcanic activity==== In 1965, the activity on the main island diminished, but at the end of May that year an eruption began at a vent off the northern shore.
Activity was short-lived, continuing until the beginning of October 1965, by which time the islet had an area of .
Once the eruptions had ceased, wave erosion rapidly wore the island away, and it disappeared beneath the waves on 24 October. During December 1965, more submarine activity occurred southwest of Surtsey, and another island was formed.
An idea of what it will look like in the future is given by the other small islands in the Vestmannaeyjar archipelago, which formed in the same way as Surtsey several thousand years ago, and have eroded away substantially since they were formed. ==Biology== ===Settlement of life=== A classic site for the study of biocolonisation from founder populations, Surtsey was declared a nature reserve in 1965, while the eruption was still in active progress.
In 2008, UNESCO declared the island a World Heritage Site, in recognition of its great scientific value. ====Plant life==== In the spring of 1965, the first vascular plant was found growing on the northern shore of Surtsey, mosses became visible in 1967, and lichens were first found on the Surtsey lava in 1970.
Activity at Jólnir was much weaker than the activity at the main vent, and even weaker than that seen at Syrtlingur, but the island eventually grew to a maximum size of in height, covering an area of , during July and early August 1966.
Like Syrtlingur, though, after activity ceased on 8 August 1966, it was rapidly eroded, and dropped below sea level during October 1966. Effusive eruptions on the main island returned on 19 August 1966, with fresh lava flows giving it further resistance to erosion.
The eruption lasted until 5 June 1967, when the island reached its maximum size of .
The eruption rate diminished steadily, though, and on 5 June 1967, the eruption ended.
In 2008, UNESCO declared the island a World Heritage Site, in recognition of its great scientific value. ====Plant life==== In the spring of 1965, the first vascular plant was found growing on the northern shore of Surtsey, mosses became visible in 1967, and lichens were first found on the Surtsey lava in 1970.
In 2008, UNESCO declared the island a World Heritage Site, in recognition of its great scientific value. ====Plant life==== In the spring of 1965, the first vascular plant was found growing on the northern shore of Surtsey, mosses became visible in 1967, and lichens were first found on the Surtsey lava in 1970.
Vestmannaeyjar also produced the famous eruption of Eldfell on the island of Heimaey in 1973.
When a large, grass-covered tussock was washed ashore in 1974, scientists took half of it for analysis and discovered 663 land invertebrates, mostly mites and springtails, the great majority of which had survived the crossing. The establishment of insect life provided some food for birds, and birds in turn helped many species to become established on the island.
Seals were found to be breeding on the island in 1983, and a group of up to 70 made the island their breeding spot.
Twelve species are now regularly found on the island. A gull colony has been present since 1984, although gulls were seen briefly on the shores of the new island only weeks after it first appeared.
The rate of subsidence was initially about per year but slowed to a year by the 1990s.
The bodies of dead birds provide sustenance for carnivorous insects, while the fertilisation of the soil and resulting promotion of plant life provides a viable habitat for herbivorous insects. The first earthworm was found in a soil sample in 1993, probably carried over from Heimaey by a bird.
In 1998, the first bush was found on the island—a tea-leaved willow (Salix phylicifolia), which can grow to heights of up to .
Slugs were found in 1998, and appeared to be similar to varieties found in the southern Icelandic mainland.
An expedition in 2004 found the first evidence of nesting Atlantic puffins, which are abundant in the rest of the archipelago. As well as providing a home for some species of birds, Surtsey has also been used as a stopping-off point for migrating birds, particularly those en route between Europe and Iceland.
In 2008, UNESCO declared the island a World Heritage Site, in recognition of its great scientific value. ====Plant life==== In the spring of 1965, the first vascular plant was found growing on the northern shore of Surtsey, mosses became visible in 1967, and lichens were first found on the Surtsey lava in 1970.
By 2008, 69 species of plant had been found on Surtsey, of which about 30 had become established.
In 2008, the 14th breeding bird species was detected with the discovery of a common raven's nest. According to a 30 May 2009 report, a golden plover was nesting on the island, with four eggs. ====Marine life==== Soon after the island's formation, seals were seen around the island.
In 2008, the 14th breeding bird species was detected with the discovery of a common raven's nest. According to a 30 May 2009 report, a golden plover was nesting on the island, with four eggs. ====Marine life==== Soon after the island's formation, seals were seen around the island.
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