Editing Surtsey (section)

==Recent development==
[[File:Surtsey from plane, 1999.jpg|thumb|250px|right|The island of Surtsey in 1999]]
[[File:North Spit of Surtsey Jan 2009.jpg|thumb|right|250px|North spit of Surtsey in January 2009]]
Following the end of the eruption, scientists established a grid of benchmarks against which they measured the change in the shape of the island. In the 20&nbsp;years following the end of the eruption, measurements revealed that the island was steadily subsiding and had lost about one metre in height. The rate of subsidence was initially about {{convert|20|cm|in|round=0.5|abbr=on}} per year but slowed to {{convert|1|–|2|cm|in|abbr=on}} a year by the 1990s. It had several causes: settling of the loose [[tephra]] forming the bulk of the volcano, compaction of sea floor [[sediment]]s underlying the island, and downward warping of the [[lithosphere]] due to the weight of the volcano.<ref>{{citation|first1=J.G.|last1= Moore|first2=Sveinn|last2=Jakobsson|first3=Josef|last3=Holmjarn|year=1992|title=Subsidence of Surtsey volcano, 1967–1991|journal=Bulletin of Volcanology|volume=55|issue= 1–2|pages=17–24|doi=10.1007/BF00301116|bibcode = 1992BVol...55...17M|s2cid= 128693202|url= https://zenodo.org/record/1232407}}</ref>

Volcanoes in the Vestmannaeyjar archipelago are typically [[monogenetic volcano|monogenetic]], 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 of its original area has been lost. The island currently loses about {{convert|1.0|ha|acre}} of its surface area each year.<ref name="jakobssen3">{{citation|last=Jakobssen|first=Sveinn P.|title=Erosion of the Island|url=http://www.surtsey.is/pp_ens/geo_2.htm|publisher=The Spurtsey Research Society|access-date=2008-07-08|date=2007-05-06}}</ref>

===Future===
[[File:Small islands in the Vestmannaeyjar archipelago, Iceland.jpg|thumb|right|250px|Other islands in the archipelago show the effects of centuries of erosion]]

As a suspected part of the [[Iceland plume]], this island is unlikely to disappear entirely in the near future. The eroded area consisted mostly of loose [[tephra]], easily washed away. Most of the remaining area is capped by hard lava flows, which are much more resistant to erosion. In addition, complex chemical reactions within the loose tephra within the island have gradually formed highly erosion-resistant [[tuff]] material, in a process known as [[Palagonite|palagonitization]]. On Surtsey, this process has happened quite rapidly, due to high temperatures not far below the surface.<ref>{{citation|last=Jakobssen|first=Sveinn P.|title=The Formation of Palagonite Tuffs|url=http://www.surtsey.is/pp_ens/geo_4.htm|publisher=The Surtsey Research Society|access-date=2008-07-08|date=2007-05-06}}</ref>

Estimates of how long Surtsey will survive are based on the rate of erosion seen up to the present day. Assuming that the current rate does not change, the island will be mostly at or below sea level by 2100. However, the rate of erosion is likely to slow as the tougher core of the island is exposed: an assessment assuming that the rate of erosion will slow exponentially suggests that the island will survive for many centuries.<ref name="Garvin 2000" /> 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.<ref name="jakobssen3" />