Tephrochronology is a geochronological technique that uses discrete layers of tephra —volcanic ash from a single eruption—to create a chronological framework in which paleoenvironmental or archaeological records can be placed. Such an established event provides a "tephra horizon". The premise of the technique is that each volcanic event produces ash with a unique chemical "fingerprint" that allows the deposit to be identified across the area affected by fallout. Thus, once the volcanic event has been independently dated, the tephra horizon will act as time marker. 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.
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Intro How did they move? What did they look like? Are they all the same species? When did they live? Lucy and other members of her species, Australopithecus afarensis , lived between 3. They are believed to be the most ancient common ancestor , or "stem" species, from which all later hominids sprang. How do we know when they lived?
How are ice cores dated?
The sole responsibility for the content of each Tentative List lies with the State Party concerned. The publication of the Tentative Lists does not imply the expression of any opinion whatsoever of the World Heritage Committee or of the World Heritage Centre or of the Secretariat of UNESCO concerning the legal status of any country, territory, city or area or of its boundaries. The clayey diatomite commonly known as "mo-clay" Moler is found only at locations in the western Lim Fjord region in the northwest of Denmark, the largest and most impressive deposits being those on the two islands of Mors and Fur.
The Minoan eruption was a major catastrophic volcanic eruption that devastated the Aegean island of Thera now called Santorini in around BCE. Although there are no clear ancient records of the eruption, its plume may have been described in the Egyptian Tempest Stele ,  and the ensuing volcanic winter coincides with a cold wave mentioned in the Chinese Bamboo Annals. Geological evidence shows the Thera volcano erupted numerous times over several hundred thousand years before the Minoan eruption.