Potassium argon dating volcanic ash Erotk lve cams
Because intrusive rocks solidify deep within the Earth away from cool water and air, volcanic glass is absent and the grains may be fairly large (that is, easily reaching lengths of one centimeter or more). In other cases, such as Austin's dacite, a partially crystallized melt erupts on the Earth's surface and produces a volcanic rock, which may be a mixture of rapidly quenched volcanic glass and coarser phenocrysts (Hyndman, 1985, p. The zoning appears as a series of concentric rings of various shades of gray within the grains (see the two obvious examples in the middle of Figure 4). Furthermore, many studies (for example, the Haulalai basalt; Funkhouser and Naughton, 1968) demonstrate that Swenson and other YECs cannot automatically assume that modern volcanic glass contains excess argon.
However, Dalrymple  found that even volcanic glass can give wrong ages and rationalized that it can be contaminated by argon from older rock material.'Clearly, Swenson simply assumes that the volcanic glass contains 'excess argon.' However, dating a mixture of older plagioclase and younger volcanic glass with inadequate equipment (hypothesis #2) does not prove that any of these components contain excess argon. No attempt was made to separate the hornblende from the Fe-Ti oxides, but further finer milling and use of heavy liquids should be considered.''The 'heavy-nonmagnetic concentrate' (DOME-1H) was dominated by orthopyroxene with much less clinopyroxene, but had a significant quantity of glassy particles attached to mafic microphenocrysts and fragments of mafic phenocrysts along incompletely fractured grain boundaries. These mafic microphenocrysts and fragments of mafic phenocrysts evidently increased the density of the attached glass particles above the critical density of 2.85 g/cc, which allowed them to sink in the heavy liquid. 9), the K-Ar method cannot be used to date samples that are much younger than 6,000 years old (Dalrymple, 1991, p. 93)Cambridge, Massachusetts, USA, performed the K-Ar dating for Austin et al. However, when they did, their website clearly stated in a footnote that their equipment could not accurately date rocks that are younger than about 2 million years old ("We cannot analyze samples expected to be younger than 2 M.