Abstract
The Surtsey marine volcano was built on the southern insular shelf of Iceland, along the seaward extension of the east volcanic zone, during episodic explosive and effusive activity from 1963 to 1967. A 1600-m-long, east-west line of 42 bench marks was established across the island shortly after volcanic activity stopped. From 1967 to 1991 a series of leveling surveys measured the relative elevation of the original bench marks, as well as additional bench marks installed in 1979, 1982 and 1985. Concurrent measurements were made of water levels in a pit dug on the north coast, in a drill hole, and along the coastline exposed to the open ocean. These surveys indicate that the dominant vertical movement of Surtsey is a general subsidence of about 1.1±0.3 m during the 24-year period of observations. The rate of subsidence decreased from 15–20 cm/year for 1967–1968 to 1–2 cm/year in 1991. Greatest subsidence is centered about the eastern vent area. Through 1970, subsidence was locally greatest where the lava plain is thinnest, adjacent to the flanks of the eastern tephra cone. From 1982 onward, the region closest to the hydrothermal zone, which is best developed in the vicinity of the eastern vent, began showing less subsidence relative to the rest of the surveyed bench marks. The general subsidence of the island probably results from compaction of the volcanic material comprising Surtsey, compaction of the sea-floor sediments underlying the island, and possibly downwarping of the lithosphere due to the laod of Surtsey. The more localized early downwarping near the eastern tephra cone is apparently due to greater compaction of tephra relative to lava. The later diminished local subsidence near the hydrothermal zone is probably due to a minor volume increase caused by hydrous alteration of glassy tephra. However, this volume increase is concentrated at depth beneath the bottom of the 176-m-deep cased drillhole.
Similar content being viewed by others
References
Emery KO, Aubrey DG (1991) Sea levels, land levels, and tide gauges. Springer-Verlag, New York, 237 pp
Jakobsson SP, Moore JG (1982) The Surtsey research drilling project of 1979. Surtsey Research Progress Report IX: 76–93
Jakobsson SP, Moore JG (1986) Hydrothermal minerals and alteration rates at Surtsey volcano, Iceland. Geol Soc Am Bull 97:648–659
Moore JG (1982) Tidal and leveling measurements on Surtsey, July–August, 1979. Surtsey Research Progress Report IX:98–101
Moore JG (1985) Structure and eruptive mechanisms at Surtsey Volcano, Iceland. Geol Mag 122:649–661
Norrman JO (1970) Trends in postvolcanic development of Surtsey island, 1972–75. Surtsey Research Progress Report V: 95–112
Thorainsson S (1968) The last phases of the Surtsey eruption. Natturufraedingurinn 38:113–135
Thorarinsson S, Einarsson Th, Sigvaldason G, Elisson G (1964) The submarine eruption off the Vestmann Island 1963–64. Bull Volcanol 27:1–11
Tomasson SG, Snorrason SP (1980) Water level measurements in the Surtsey drillhole of 1979, Iceland. Unpublished report, Orkustofnun (National Energy Authority), 12 pp
Tryggvason E (1968) Result of precision leveling in Surtsey. Surtsey Research Progress Report IV:149–158
Tryggvason E (1970) Precision leveling in Surtsey. Surtsey Research Progress Report V:113–116
Tryggvason E (1972) Precision leveling in Surtsey. Surtsey Research Progress Report VI:158–162
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Moore, J.G., Jakobsson, S. & Holmjarn, J. Subsidence of Surtsey volcano, 1967–1991. Bull Volcanol 55, 17–24 (1992). https://doi.org/10.1007/BF00301116
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00301116