Editing Surtsey (section)

====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"/>