A microatoll is a circular colony of coral, dead on the top but living around the perimeter. Growth is mainly lateral, as upward growth is limited by exposure to air. Microatolls may be up to 6 meters (20 ft) in diameter.[2] They are named for their resemblance to island atolls formed during the subsidence of volcanic islands, as originally suggested by Darwin (1842).[3]
In intertidal reef-flat environments, massive Porites form characteristic microatoll formations, with living coral around the perimeter and dead skeleton on the exposed upper surface.[1]
They act as natural recorders of sea level, which allows the monitoring of sea level changes in response to global warming. They have also been used to quantify and date changes in relative sea level in seismically active areas,[4] and to provide information on changes in sea surface temperature using oxygen isotope values as a proxy.[5]
The term 'microatoll' was first used by Krempf in 1927, although his description lacks a precise definition. Kuenen defined it in 1933 as "a colony of corals" with "a raised rim, more or less completely surrounding a lower, dead surface".[2] This definition has been extended to include similar structures built by non-coral reef-building organisms such as serpulid worms, pelecypods and vermetidgastropods.
The detailed record of sea level change preserved in fossil microatolls, combined with precise dating of individual annual rings using the Uranium-thorium dating method, allows them to be used to determine past relative sea-level change with uncertainties of about 20 centimeters (7.9 in) in level and a few years to a few decades in time.[4] They have been used to map the rupture areas of great to giant earthquakes and to estimate the recurrence interval of such events before historic records are available.[6]
Sea surface temperaturesedit
Changes in oxygenisotope ratios in fossil microatolls have also been used to provide high-resolution proxy records for sea surface temperature over the last few thousand years.[7]
^van Woesik, R., Golbuu, Y. and Roff, G. (2015) "Keep up or drown: adjustment of western Pacific coral reefs to sea level rise in the 21st century". Royal Society, open science, 2 (7): 150181. doi:10.1098/rsos.150181
^ abcStoddart, D.R.; Scoffin T.P. (1979). "Microatolls: review of form, origin and terminology" (PDF). Atoll Research Bulletin. 224: 1–17. doi:10.5479/si.00775630.224.1.
^Darwin, Charles (1842). The structure and distribution of coral reefs. London: Smith, Elder and Co. p. 214.
^ abNatawidjaja, D. H.; Sieh K.; Chlieh M.; Galetzka J.; Suwargadi B.W.; Cheng H.; Edwards R.L.; Avouac J.-P.; Ward S. N. (2006). "Source parameters of the great Sumatran megathrust earthquakes of 1797 and 1833 inferred from coral microatolls" (PDF). Journal of Geophysical Research. 111 (B06403): n/a. Bibcode:2006JGRB..111.6403N. doi:10.1029/2005JB004025. hdl:10220/8480.
^ abWoodroffe, C. (2004). Goudie A. (ed.). Encyclopedia of geomorphology, Volume 2. Routledge. pp. 670–671. ISBN9780415327381. Retrieved 2009-10-30.
^Woodroffe, C.D.; Beech M.R.; Gagan M.K. (2003). "Mid-late Holocene El Niño variability in the equatorial Pacific from coral microatolls". Geophysical Research Letters. 30 (7): 1358. Bibcode:2003GeoRL..30.1358W. doi:10.1029/2002GL015868. Retrieved 2009-10-30.
January 01, 1970
microatoll, microatoll, circular, colony, coral, dead, living, around, perimeter, growth, mainly, lateral, upward, growth, limited, exposure, meters, diameter, they, named, their, resemblance, island, atolls, formed, during, subsidence, volcanic, islands, orig. A microatoll is a circular colony of coral dead on the top but living around the perimeter Growth is mainly lateral as upward growth is limited by exposure to air Microatolls may be up to 6 meters 20 ft in diameter 2 They are named for their resemblance to island atolls formed during the subsidence of volcanic islands as originally suggested by Darwin 1842 3 In intertidal reef flat environments massive Porites form characteristic microatoll formations with living coral around the perimeter and dead skeleton on the exposed upper surface 1 They act as natural recorders of sea level which allows the monitoring of sea level changes in response to global warming They have also been used to quantify and date changes in relative sea level in seismically active areas 4 and to provide information on changes in sea surface temperature using oxygen isotope values as a proxy 5 Contents 1 Terminology 2 Occurrence 3 In climate research 3 1 Paleogeodesy 3 2 Sea surface temperatures 4 See also 5 ReferencesTerminology editThe term microatoll was first used by Krempf in 1927 although his description lacks a precise definition Kuenen defined it in 1933 as a colony of corals with a raised rim more or less completely surrounding a lower dead surface 2 This definition has been extended to include similar structures built by non coral reef building organisms such as serpulid worms pelecypods and vermetid gastropods Occurrence editMicroatolls are found only in corals that grow in the lower intertidal zone on shallow reef flats 5 Microatolls are formed by several species of the genus Porites but examples have also been described from Acropora Heliopora Favia Favites Platygyra Cyphastrea and Goniastrea 2 In climate research editPaleogeodesy edit The detailed record of sea level change preserved in fossil microatolls combined with precise dating of individual annual rings using the Uranium thorium dating method allows them to be used to determine past relative sea level change with uncertainties of about 20 centimeters 7 9 in in level and a few years to a few decades in time 4 They have been used to map the rupture areas of great to giant earthquakes and to estimate the recurrence interval of such events before historic records are available 6 Sea surface temperatures edit Changes in oxygen isotope ratios in fossil microatolls have also been used to provide high resolution proxy records for sea surface temperature over the last few thousand years 7 See also edit1833 Sumatra earthquakeReferences edit van Woesik R Golbuu Y and Roff G 2015 Keep up or drown adjustment of western Pacific coral reefs to sea level rise in the 21st century Royal Society open science 2 7 150181 doi 10 1098 rsos 150181 a b c Stoddart D R Scoffin T P 1979 Microatolls review of form origin and terminology PDF Atoll Research Bulletin 224 1 17 doi 10 5479 si 00775630 224 1 Darwin Charles 1842 The structure and distribution of coral reefs London Smith Elder and Co p 214 a b Natawidjaja D H Sieh K Chlieh M Galetzka J Suwargadi B W Cheng H Edwards R L Avouac J P Ward S N 2006 Source parameters of the great Sumatran megathrust earthquakes of 1797 and 1833 inferred from coral microatolls PDF Journal of Geophysical Research 111 B06403 n a Bibcode 2006JGRB 111 6403N doi 10 1029 2005JB004025 hdl 10220 8480 a b Woodroffe C 2004 Goudie A ed Encyclopedia of geomorphology Volume 2 Routledge pp 670 671 ISBN 9780415327381 Retrieved 2009 10 30 Meltzner A J Sieh K Chiang H W Philibosian B E Suwargadi B W Natawidjaja D H 2009 Coral microatoll paleogeodesy on Simeulue Island Sumatra reveals earthquake clusters and persistent rupture segmentation 2009 Portland GSA Annual Meeting Retrieved 2009 10 30 Woodroffe C D Beech M R Gagan M K 2003 Mid late Holocene El Nino variability in the equatorial Pacific from coral microatolls Geophysical Research Letters 30 7 1358 Bibcode 2003GeoRL 30 1358W doi 10 1029 2002GL015868 Retrieved 2009 10 30 Retrieved from https en wikipedia org w index php title Microatoll amp oldid 1122428636, wikipedia, wiki, book, books, library,
