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Encyclopedia > Vaalbara

The Earth's first supercontinent thought to have existed is Vaalbara. According to radiometric data of the encompassing cratons that comprised Vaalbara, we know that it existed at 3.1 billion years ago (3.1 Ga) and possibly even as far back as 3.6 Ga. Evidence includes geochronological and palaeomagnetic studies between the two Archaean cratons (protocontinents) called the Kaapvaal craton (the Kaapvaal province of South Africa) and the Pilbara craton (the Pilbara province of Western Australia). Another piece of evidence is the structural sequence similarities of the greenstone belts and gneiss belts of these two cratons. These same Archaean greenstone belts are now spread out across the margins of the Superior craton of Canada and are also spread out across the cratons of the former Gondwana and Laurasia continents. The subsequent drift paths of the Kaapvaal and Pilbara cratons after 2.8 Ga gives further evidence that they were once connected. In geology, a supercontinent is a land mass comprising more than one continental core, or craton. ... In telecommunication and physics, radiometry is the science of radiation measurement. ... A craton is an old and stable part of the continental crust that has survived the merging and splitting of continents and supercontinents for at least 500 million years. ... Geochronology is the science of determining the age of rocks, fossils, and sediments. ... Paleomagnetism refers to the orientation of the Earths magnetic field as it is preserved in various magnetic iron bearing minerals throughout time. ... The Archean is a geologic eon; it is a somewhat antiquated term for the time span between 2500 million years before the present and 3800 million years before the present. ... A craton is an old and stable part of the continental crust that has survived the merging and splitting of continents and supercontinents for at least 500 million years. ... Emblems: Floral - Kangaroo Paw (Anigozanthos manglesii); Mammal - Numbat (Myrmecobius fasciatus); Bird - Black Swan (Cygnus atratus) Motto: Cygnis Insignis (Distinguished by its swans) Slogan or Nickname: Wildflower State Other Australian states and territories Capital Perth Government Const. ... This article is about zones of mixed sedimentary and volcanic rock sequences that often contain minable concentrations of gold, silver, copper, zinc and lead. ... Gneiss Gneiss is a common and widely distributed type of rock formed by high-grade regional metamorphic processes from preexisting formations that were originally either igneous or sedimentary rocks. ... Pangaea was formed by the merging of two continents, Laurasia and Gondwana East African and Kuungan Orogens 550 Ma reconstruction showing final stages of assembly The southern supercontinent Gondwana (originally Gondwanaland) included most of the landmasses which make up todays continents of the southern hemisphere, including Antarctica, South America... Laurasia was a supercontinent that most recently existed as a part of the split of the Pangaean supercontinent in the late Mesozoic era. ... To meet Wikipedias quality standards, this article or section may require cleanup. ...


It is not certain when Vaalbara began to break up, but geochronological and palaeomagnetic evidence show that the two cratons had a rotational 30 degree latitudinal separation at 2.78 to 2.77 Ga, implying that they were no longer contiguous after ~2.8 Ga.


References

  • Bailey, R.C., Cruden, A.R., and B. Nitescu. (2006) "Crustal structure and implications for the tectonic evolution of the Archean Western Superior craton from forward and inverse gravity modeling." Tectonics, vol. 25. Online Abstract: http://www.agu.org/pubs/crossref/2006/2004TC001717.shtml
  • Dann, J., M. J. de Wit, S. H. White, and E. Zegers. (1998) Vaalbara, Earth's oldest assembled continent? A combined. structural, geochronological, and palaeomagnetic test." Online: http://www.geo.uu.nl/Research/Paleomagnetism/publications/Zegers98b.pdf
  • Wingate, M.T.D. (1998) “palaeomagnetic test of the Kaapvaal-Pilbara (Vaalbara) connection at 2.78 Ga.” South African Journal of Geology; December 1998; v. 101; no. 4; p. 257-274 Australian National University, Research School of Earth Sciences, Canberra, Australia. Online Abstract: http://sajg.geoscienceworld.org/cgi/content/abstract/101/4/257
  • Zegers, T.E., and A. Ocampo. (2003) "Vaalbara and Tectonic Effects of a Mega Impact in the Early Archaen 3470 Ma." European Space Agency, ESTEC, SCI-SB, Keplerlaan 1, 2201 AZ Noordwijk. Online: http://www.lpi.usra.edu/meetings/largeimpacts2003/pdf/4038.pdf

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Geological supercontinents :  Gondwana · Laurasia · Pangaea · Pannotia · Rodinia · Columbia · Kenorland · Ur · Vaalbara


 
 

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