Mazama Ash: Difference between revisions

The climactic eruption of Mount Mazama during which the Mazama Ash was ejected occurred approximately 6790 ± 15 [[Radiocarbon calibration|¹⁴C yrs]] [[Before Present|BP]], or 7640 ± 20<ref name=":0" /> calibrated years [[Before Present]] (5677 ± 150 [[Common Era|B.C.E.)]], based on analysis of multiple ash and [[tephra]] sources throughout the [[Pacific Northwest]], as well as by other methods such as identification of ash from within an [[ice core]] from the [[Greenland Ice Sheet Project]] <ref name=Age /> and from [[Core sample|sediment cores]] from the [[Lake Superior|Lake]]<ref>{{Cite journal |last=Spano |first=N.G. |last2=Lane |first2=C.S. |last3=Francis |first3=S.W. |last4=Johnson |first4=T.C. |date=2017-12-01 |title=Discovery of Mount Mazama cryptotephra in Lake Superior (North America): Implications and potential applications |url=https://pubs.geoscienceworld.org/geology/article-lookup?doi=10.1130/G39394.1 |journal=Geology |language=en |volume=45 |issue=12 |pages=1071–1074 |doi=10.1130/G39394.1 |issn=0091-7613}}</ref> [[Lake Superior|Superior]] basin.

The Mazama ash spread over an area of at least {{convert|900000|km2|sqmi|abbr=on}} in the northern Great Plains, where it is most commonly preserved within [[peat]], [[alluvium|alluvial]], [[lacustrine deposits|lacustrine]], and [[aeolian processes#deposition|aeolian]] [[sediment]]s.<ref name=David>David, P.P. 1970. Discovery of Mazama Ash in Saskatchewan, Canada. Canadian Journal of Earth Sciences, vol. 7, p. 1579-1583.</ref>

In the U.S., it is present in portions of the [[U.S. state]]s of [[California]], [[Oregon]], [[Washington (state)|Washington]], [[Idaho]], [[Montana]], [[Nevada]], [[Wyoming]] and [[Utah]].<ref name=White>White, J.M. and Osborn, G. 1992. Evidence for a Mazama-like tephra deposited ca. 10 000 B.P. at Copper Lake, Banff National Park, Alberta; Fig. 1 (inset), p. 53. Canadian Journal of Earth Sciences, vol. 29, p. 52-62.</ref>

Comparison with the effects of the [[Mount St. Helens]] eruption of 1980 indicates that the Mazama Ash would have covered the landscape in a blanket up to 15 &nbsp;cm (6 &nbsp;in) thick, coating vegetation and clogging watercourses throughout the ashfall area. This would have caused an immediate scarcity of resources for the native people and wildlife, necessitating the movement of people out of the main ashfall area. Available archeological evidence from a site in the [[Cypress Hills (Canada)|Cypress Hills]] of southern Alberta suggests a hiatus in human occupation of the ash-affected area there of perhaps 200 years.<ref name=Oetelaar /><ref name=Beaudoin />

The particles and gasses released during the Mazama eruption caused climate cooling. Studies of the Greenland ice core suggest that the eruption produced a substantial [[stratospheric sulfur aerosols|stratospheric aerosol loading]] spread over a period about 6 years. This may have produced a temperature depression of about 0.6 to 0.7 &nbsp;°C at mid to high northern latitudes for 1 to 3 years. The release of [[chlorine]] during the eruption may also have led to substantial depletion of stratospheric [[ozone]].<ref name=Age />