Victoria C. Smith, 2014. "Volcanic markers for dating the onset of the Anthropocene", A Stratigraphical Basis for the Anthropocene, C. N. Waters, J. A. Zalasiewicz, M. Williams, M. Ellis, A. M. Snelling
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Volcanic ash is dispersed over thousands of kilometres during large-scale eruptions, forming sedimentary layers. These ash (tephra) deposits are increasingly being used as unique marker layers in a variety of sedimentary archives including ice cores, and terrestrial and marine records. Tephra dispersed during large explosive eruptions that coincide with the defined beginning of the Anthropocene could therefore be used to help identify this event in various archives, and assess the relative spatial differences in marked anthropogenic change. The 1815 eruption of Tambora, Indonesia, was the largest in historical time and occurred in the middle of Europe’s Industrial Revolution. Volatile emissions injected into the atmosphere during this eruption caused widespread effects including the ‘year without a summer’ during which there were anomalously cooler temperatures recorded across much of North America and Europe. Sulphate aerosols associated with the eruption were dispersed by stratospheric and tropospheric winds across the entire globe. Deposits of these are clearly recorded in the Earth’s key palaeoclimatic records: polar ice cores. Significantly, the Tambora eruption occurred immediately prior to substantial increases in greenhouse gases, a defining feature of the Anthropocene.
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Humankind has pervasively influenced the Earth’s atmosphere, biosphere, geosphere, hydrosphere and cryosphere, arguably to the point of fashioning a new geological epoch, the Anthropocene. To constrain the Anthropocene as a potential formal unit within the Geological Time Scale, a spectrum of indicators of anthropogenically-induced environmental change is considered, and shown as stratigraphical signals that may be used to characterize an Anthropocene unit, and to recognize its base. This volume describes a range of evidence that may help to define this potential new time unit and details key signatures that could be used in its definition. These signatures include lithostratigraphical (novel deposits, minerals and mineral magnetism), biostratigraphical (macro- and micro-palaeontological successions and human-induced trace fossils) and chemostratigraphical (organic, inorganic and radiogenic signatures in deposits, speleothems and ice and volcanic eruptions). We include, finally, the suggestion that humans have created a further sphere, the technosphere, that drives global change.