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536 ad wars4/5/2023 There are small acid layers associated with 528 and 533, but they are not sufficiently strong that they can be related to a super-volcano ( Clausen et al. None of these has found evidence for a significant acid layer around 536 of the sort that would be caused by the eruption of a super-volcano. Numerous ice-core studies have been carried out in both Greenland and Antarctica (see, for example, Clausen et al. This acidity would be recorded in the polar ice caps. Secondly, a super-volcano would be expected to produce significant acidity in the atmosphere. Firstly, no terrestrial volcano can be satisfactorily identified with this event. The super-volcano theory has several problems. The alternative scenario invokes an impact by an asteroid or comet ( Clube and Napier 1984). One idea is that a giant “super-volcano” erupted in 536, causing the effects described above ( Stothers 1984, Keys 1999). There have been two theories put forward to account for this cataclysmic climatic event. However, he may have been describing the actual events taking place at this time. Previously Gildas has been thought to have been talking allegorically, with his many biblical references. The sixth-century British monastic writer Gildas talks of large-scale fires and widespread destruction of the landscape at around the same time ( Winterbotham 1978). “the Sun was dark and its darkness lasted for eighteen months each day it shone for about four hours, and still this light was only a feeble shadow”. “the Sun gave forth its light without brightness, like the Moon, during this whole year, and it seemed exceedingly like the Sun in eclipse”,Īnd Michael the Syrian ( Chabot 1901) states: Mediterranean historians also record a “dry fog” event. Chinese records refer to obscured skies and summer frosts ( Baillie 1999). There are also some limited historical records from the same period, which record the presence of a “dust veil”. (Right) US foxtail pine chronologies (adapted from Scuderi 1990). (Left) Irish oak trees (adapted from Baillie 1999). Figure 1 shows the typical variation in tree-ring widths.ĭendrochronological data showing the decreases in the rate of tree-ring growth for the years around AD 540. 1990), and a study of European oak tree data as a whole shows that the event starts in 536 and lasts until 545 ( Baillie 1994). A similar effect is seen in Fennoscandian pine trees ( Briffa et al. Dendrochronological (tree-ring) evidence in oak trees salvaged from Irish peat bogs indicates a sequence of colder than average summers at this time ( Baillie 1991, 1999). In AD 536 an event occurred which caused significant climatic change. Airbursts can also produce a high-altitude haze of particles, such as was seen in the 1908 Tunguska event. An airbursting object releases energy in the form of a shockwave, which can devastate large areas and trigger forest fires. Depending on the size and strength of the material of the meteoroid, it may explode in the atmosphere before reaching the ground. In fact, the UK government even set up a Near Earth Object Task Force to evaluate the risks of impacts from such objects ( Atkinson et al. Objects of this size are generally more of a hazard. Asteroids are primarily rocky or metallic in composition, whereas comets are composed mainly of a variety of ices with some rock. However, there are also much less frequent collisions with larger objects ranging in size from tens of metres to kilometres across, which may be asteroids or comets. These objects are known as meteoroids which, as they run into the Earth's atmosphere, produce meteors − also known as shooting stars. The majority of this debris takes the form of very small particles of dust. The Earth is bombarded every day by debris from space.
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