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Encyclopedia > Tephrochronology

Tephrochronology is a geochronolgical technique that utilises discreet layers of tephra—volcanic ash from a single eruption— to create a chronological framework in which palaeoenvironmental or archaeological records can be placed. Such an established event provides a "tephra horizon". Geochronology is the science of determining the age of rocks, fossils, and sediments. ... Tephra refers to air-fall material produced by a volcanic eruption regardless of composition or fragment size. ... Archaeology or archeology (from the Greek words αρχαίος = ancient and λόγος = word/speech/discourse) is the study of human cultures through the recovery, documentation and analysis of material remains and environmental data, including architecture, artifacts, biofacts, human remains, and landscapes. ...


The main advantages of the technique are that the volcanic ash layers can be relatively easily identified in many sediments and that the tephra layers are deposited relatively instantaneously over a wide spatial area. This means they provide accurate temporal marker layers which can be used to verify or corroborate other dating techniques, linking sequences widely separated by location into a unified chronology. Diamond Head, a well-known backdrop to Waikiki in Hawaii, is an ash cone that solidified into tuff Volcanic ash is the term for very fine rock and mineral particles less than 2 mm in diameter that are ejected from a volcanic vent. ...


The problems associated with tephochronology are that its use has been limited to areas of frequent large scale volcanic activity and that tephra chemistry can become altered over time. It also requires accurate geochemical fingerprinting (usually via an electron microprobe) and radiometric dating dating of proximal tephra deposits. The electron microprobe is a non-destructive analytical tool used to determine the chemical composition of small volumes of solid materials. ... Radiometric dating is a technique used to date materials based on a knowledge of the decay rates of naturally occurring isotopes, and the current abundances. ...


Major volcanoes which have been used in tephrochronological studies include Vesuvius, Hekla and Santorini. Minor volcanic events may also leave their fingerprint in the geological record: Saksunarvatn_tephra form a horizon in the late Pre-Boreal of Northern Europe. Mount Vesuvius (Italian: Monte Vesuvio) is a volcano east of Naples, Italy, located at 40°49′N 14°26′ E. It is the only active volcano on the European mainland, although it is not currently erupting. ... Hekla is a volcano located in the south of Iceland at 63. ... Map of Santorini. ... The Boreal in paleoclimatology was the first Blytt-Sernander period, pollen zone and chronozone of Holocene north Europe. ...


Since the late 1990s, techniques developed by C.S.M. Turney and others for extracting tephra horizons invisible to the naked eye ("cryptotephra") have revolutionised the application of tephrochronology. This technique relies upon the difference between the specific gravity of the tephra shards and the host sediment matrix. It has led to the first discovery of the Vedde Ash on the mainland of Britain, in Sweden and in two sites on the Karelian Isthmus of Baltic Russia. It has also revealed previously undetected ash layers, such as the hitherto unrecorded Borrobol Tephra, dated to ca. 14,400 years BP calibrated (Wastegård 2004). The Karelian Isthmus is the narrow stretch of land between the Gulf of Finland and Lake Ladoga in northwestern Russia. ...


References

  • Dugmore, A. and Buckland, P.C. "Tephrochronology and Late Holocene soil erosion in South Iceland." in 'Environmental Change in Iceland: Past and Present' (eds. J.K. Maizels and C. Caseldine). Dordrecht: Kluwer Academic Publishers, pp. 147-159, 1991.
  • Þórinsson, S. "Tephrochronology in medieval Iceland." in 'Scientific Methods in Medieval Archaeology (ed. R. Berger). Berkeley: University of California Press, pp. 295-328, 1970.

External links

  • USGS tephrochronology technique
  • Tephra and Tephrochronology, The University of Edinburgh
  • Antarctic Research Group
  • TEPHROCHRONOLOGY AND HIGH-PRECISION ANALYSIS
  • TephraBase
  • International Arctic Workshop, 2004. Stefan Wastegård et al., "Towards a tephrochronology framework for the last glacial/interglacial transition in Scandinavia and the Faroe Islands": (Abstract)

  Results from FactBites:
 
Faculty: Andrew Dugmore (545 words)
My research is focused on the development and environmental applications of tephrochronology, a dating technique based on the identification and correlation of layers of volcanic ash.
Tephrochronology can be used to accurately constrain both spatially referenced data sets and models of the human dimensions of environmental change.
Application of tephrochronology in detailed studies of glacier-environment interactions and the impact of climate change involve international collaborations and joint research with Kirkbride (U Dundee, Scotland).
Tephrochronology (249 words)
The Tephrochronology facility was established in 1996 and is engaged in a range of Research, Service and Knowledge Transfer activities.
Tephrochronology is based on the identification of rapidly deposited particles of volcanic ash (tephra) by geochemical fingerprinting.
Tephrochronologies have been developed in many regions of Europe (including the British Isles), the Americas, Asia and Africa.
  More results at FactBites »

 
 

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