One method for dating the core is tephrochronolog, that is, locating fallout from known volcanic eruptions.
. Electrical conductivity measurements are made along the entire length of the core. Increases in celectrical onductivity indicate the presence of volcanic eruption fallout. Sections of the ice are melted and filtered through a capillary-pore membrane filter. An automated scanning electron microscope equipped for x-ray microanalysis is used to determine the size, shape and elemental composition of hundreds of particles on the filter
Cluster analysis, a multivariate statistical routine, of the elemental compositions of sodium, magnesium, aluminum, silicon, potassium, calcium, titanium and iron is done to identify the volcanic glass particles in the sample. Representative glass particles are re-located for photomicrography and more detailed chemical analysis.
Tephra collected from near the volcanic eruption that may have produced the fallout in the core is ground to a fine powder, dispersed in liquid and filtered through a capillary-pore membrane. Automated SEM analysis is used on the tephra sample to obtain representative elemental composition for the volcanic glass for compariuson with the glass particles found in the ice core. Fallout from several know volcanic eruptions have been found in Greenland.
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