Editing Surtsey (section)

===Formation===
{| class="wikitable"
|+'''Scheme of the [[Surtseyan eruption]]'''
|-
| rowspan="9"| [[File:Surtseyan Eruption-numbers.svg|200px]]
|1: Water vapour cloud
|-
|2: Cypressoid ash jet
|-
|3: Crater
|-
|4: Water
|-
|5: Layers of lava and ash
|-
|6: Stratum
|-
|7: Magma conduit
|-
|8: Magma chamber
|-
|9: Dike
|}

The eruption was unexpected, and almost certainly began some days before it became apparent at the surface. The sea floor at the eruption site is {{convert|130|m|ft|abbr=off}} below sea level, and at this depth volcanic emissions and explosions would be suppressed, quenched and dissipated by the water pressure and density. Gradually, as repeated flows built up a mound of material that approached sea level, the explosions could no longer be contained, and activity broke the surface.<ref name="Decker">{{citation | last1 = Decker | first1 = Robert | last2 = Decker | first2 = Barbara | title = Volcanoes | publisher = Freeman | year = 1997 | location = New York | isbn = 978-0-7167-3174-0 }}</ref>

The first noticeable indications of volcanic activity were recorded at the seismic station in [[Kirkjubæjarklaustur]], Iceland from 6 to 8 November 1963, which detected weak tremors emanating from an [[epicentre]] approximately west-south-west at a distance of {{convert|140|km|mi|abbr=on}}, the location of Surtsey. Another station in [[Reykjavík]] recorded even weaker tremors for ten hours on 12 November at an undetermined location, when seismic activity ceased until 21 November.<ref name="Sigtryggson">{{citation | first1 = Hlynur | last1 = Sigtryggsson | last2 = Sigurðsson | first2 = Eiríkur | title = Earth Tremors from the Surtsey Eruption 1963–1965: a preliminary survey | journal = Surtsey Research Progress Report II | pages = 131–138 | year = 1966 | url = http://www.surtsey.is/pp_ens/report/report_II.htm | access-date =2008-07-08}}</ref> That same day, people in the coastal town of [[Vík]] {{convert|80|km|mi|abbr=on}} away noticed a smell of [[hydrogen sulfide|hydrogen sulphide]].<ref name="Decker"/> On 13 November, a fishing vessel in search of herring, equipped with sensitive thermometers, noted sea temperatures {{convert|3.2|km|mi|1|abbr=on}} SW of the eruption center were {{convert|2.4|C-change|F-change}} higher than surrounding waters.<ref>{{citation | first = Svend-Aage | last = Malmberg | title = The temperature effect of the Surtsey eruption: a report on the sea water | journal = Surtsey Research Progress Report I | pages = 6–9 | year = 1965 | url = http://www.surtsey.is/pp_ens/report/report_I.htm | access-date =2008-07-08}}</ref>

====Eruption at the surface====
[[File:Surtsey eruption 2.jpg|thumb|right|250px|Surtsey's ash column rises over the newly forming island]]

At 07:15 [[Greenwich Mean Time|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. The captain thought it might have been a boat on fire, and ordered his crew to investigate. Instead, they encountered explosive eruptions giving off black columns of ash, indicating that a volcanic eruption had begun to breach the surface of the sea.<ref name="Decker"/> By 11:00 the same day, the [[eruption column]] had reached several kilometres in height. At first the eruptions took place at three separate vents along a northeast by southwest trending [[fissure vent|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 {{convert|500|m|ft|0|abbr=off}} in length and had reached a height of {{convert|45|m|ft|abbr=off}}.<ref name="Thorarinsson I">{{citation | first = Sigurður | last = Þórarinsson |author-link=Sigurður Þórarinsson | title = The Surtsey eruption: Course of events and the development of the new island. | journal = Surtsey Research Progress Report I | pages = 51–55 | year = 1965 | url = http://www.surtsey.is/pp_ens/report/report_I.htm | access-date =2008-07-08}}</ref>

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 24 November, the island measured about {{convert|900|by|650|m|ft}}. 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 Ocean|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 {{convert|1300|m|ft|0|abbr=off}}.<ref name="Decker" />

The explosive [[Phreatic eruption|phreatomagmatic]] eruptions caused by the easy access of water to the erupting vents threw rocks up to a kilometre (0.6&nbsp;mi) away from the island, and sent [[Volcanic ash|ash]] clouds as high as {{convert|10|km|mi|abbr=on}} up into the [[Atmosphere of Earth|atmosphere]]. The loose pile of unconsolidated [[tephra]] would quickly have been washed away had the supply of fresh magma dwindled, and large clouds of dust were often seen blowing away from the island during this stage of the eruption.<ref name="Decker" />

The new island was named after the fire ''[[jötunn]]'' [[Surtur]] from [[Norse mythology]] (''Surts'' is the [[genitive case]] of ''Surtur'', plus [[:wikt:ey|-ey]], ''island'') by the [[Icelandic Naming Committee]].<ref>{{cite book| title=Surtsey: the Newest Place on Earth |last1= Lasky|first1= Kathryn|last2=Knight | first2=Christopher |pages=22–23 | url=https://archive.org/details/surtseynewestpla0000lask_w0j7/page/22/mode/2up | publisher=Seymour Science | date=1996 | isbn=9781623342999}}</ref> Three French journalists representing the magazine ''[[Paris Match]]'' notably landed there on 6 December 1963, staying for about 15&nbsp;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.<ref>{{citation|last=Doutreleau|first=Vanessa|title=Surtsey, naissances d'une île|journal=Ethnologie Française|publisher=Presses Universitaires de France|volume=XXXVII|issn=0046-2616|isbn=978-2-13-055455-4|pages=421–433|year=2006|url=http://www.cairn.info/article.php?ID_REVUE=ETHN&ID_NUMPUBLIE=ETHN_063&ID_ARTICLE=ETHN_063_0421|access-date=2008-07-08|doi=10.3917/ethn.063.0421|issue=3|language=fr}}</ref>

====Permanent island====
By early 1964, 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 eruption|explosive]]. Instead, [[lava fountain]]s and [[lava flow|flows]] became the main form of activity. These resulted in a hard cap of extremely erosion-resistant rock being laid down on top of much of the loose volcanic pile, which prevented the island from being washed away rapidly. [[Effusive eruption]]s continued until 1965, by which time the island had a surface area of {{convert|2.5|km2|abbr=on}}.<ref name="Decker" />

On 28 December 1963, [[Submarine eruption|submarine activity]] to the northeast of Surtsey began, causing the formation of a ridge {{convert|100|m|ft|abbr=on}} high on the sea floor. This [[seamount]] was named [[Surtla]] {{IPA|is|ˈsʏr̥tla|}}, but never reached sea level. Eruptions at Surtla ended on 6 January 1964, and it has since been eroded from its minimum depth of {{convert|23|to|47|m|ft|abbr=on}} below sea level.<ref name="Norrman">{{citation|first1 = John | last1 = Norrman | last2 = Erlingsson | first2 = Ulf |author-link1=John O. Norrman | title = The submarine morphology of Surtsey volcanic group | journal = Surtsey Research Progress Report X | pages = 45–56 | year = 1992 | url = http://www.surtsey.is/pp_ens/report/report_X.htm | access-date =2008-07-08}}</ref>

====Subsequent volcanic activity====
[[File:Surtsey craters.jpg|left|thumb|250px|The eruption vents in 1999]]

In 1965, the activity on the main island diminished, but at the end of May that year an eruption began at a vent {{convert|0.6|km|mi|abbr=on}} off the northern shore. By 28 May, an island had appeared, and was named [[Syrtlingur]] ({{IPA|is|ˈsɪr̥tliŋkʏr̥|}} Little Surtsey). The new island was washed away during early June, but reappeared on 14 June. Eruptions at Syrtlingur were much smaller in scale than those that had built Surtsey, with the average rate of emission of volcanic materials being about a tenth of the rate at the main vent. Activity was short-lived, continuing until the beginning of October 1965, by which time the islet had an area of {{convert|0.15|km2|abbr=on}}. Once the eruptions had ceased, wave erosion rapidly wore the island away, and it disappeared beneath the waves on 24 October.<ref name ="Thorarinsson II">{{citation | first = Sigurður | last = Þórarinsson | title = The Surtsey eruption: course of events and the development of Surtsey and other new islands | journal = Surtsey Research Progress Report II | pages = 117–123 | year = 1966 | url = http://www.surtsey.is/pp_ens/report/report_II.htm | access-date =2008-07-08}}</ref>

During December 1965, more submarine activity occurred {{convert|0.9|km|mi|abbr=on}} southwest of Surtsey, and another island was formed. It was named [[Jólnir]], and over the following eight months it appeared and disappeared several times, as wave erosion and volcanic activity alternated in dominance. 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 {{convert|70|m|ft|abbr=on}} in height, covering an area of {{convert|0.3|km2|abbr=on}}, 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.<ref name="Thorarinsson III">{{citation | first = Sigurður | last = Þórarinsson | title = The Surtsey eruption: course of events during the year 1966 | journal = Surtsey Research Progress Report III | pages = 84–90 | year = 1967 | url = http://www.surtsey.is/pp_ens/report/report_III.htm | access-date =2008-07-08}}</ref>

Effusive eruptions on the main island returned on 19 August 1966, with fresh lava flows giving it further resistance to erosion. The eruption rate diminished steadily, though, and on 5 June 1967, the eruption ended. 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 (0.24&nbsp;cu&nbsp;mi), and the island's highest point was {{convert|174|m|ft|abbr=off}} above sea level at that time.<ref name="Decker" />

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 {{convert|0.024|km3|abbr=on}} of material has been lost due to erosion—this represents about a quarter of the original above-sea-level volume of the island.<ref name="Garvin 2000">{{citation | first1 = J.B. | last1 = Garvin | first2 = R.S. | last2 = Williams Jr | first3 = J.J. | last3 = Frawley | first4 = W.B. | last4 = Krabill | title = Volumetric evolution of Surtsey, Iceland, from topographic maps and scanning airborne laser altimetry | journal = Surtsey Research Progress Report XI | pages = 127–134 | year = 2000 | url = http://www.surtsey.is/pp_ens/report/report_XI.htm | access-date =2008-07-08}}</ref><ref>{{citation| title=Surtsey Topography| publisher= NASA| date=1998-11-12| url=http://denali.gsfc.nasa.gov/research/garvin/surtsey.html| archive-url=https://web.archive.org/web/19990128220224/http://denali.gsfc.nasa.gov/research/garvin/surtsey.html| url-status=dead| archive-date=1999-01-28| access-date=2008-07-08}}</ref> Its maximum elevation has diminished to {{convert|155|m|ft|abbr=on}}.<ref name="Vésteinsson"/>