Dynamic observations of vesiculation reveal the role of silicate crystals in bubble nucleation and growth in andesitic magmas

Bubble nucleation and growth control the explosivity of volcanic eruptions, and the kinetics of these processes are generally determined from examinations of natural samples and quenched experimental run products. These samples, however, only provide a view of the final state, from which the initial conditions of a time-evolving magmatic system are then inferred. The interpretations that follow are inexact due to the inability of determining the exact conditions of nucleation and the potential detachment of bubbles from their nucleation sites, an uncertainty that can obscure their nucleation location \u2013 either homogeneously within the melt or heterogeneously at the interface between crystals and melts. We present results of a series of dynamic, real-time 4D X-ray tomographic microscopy experiments where we observed the development of bubbles in crystal bearing silicate magmas. Experimentally synthesized andesitic glasses with 0.25\u20130.5 wt% H2O and seed silicate crystals were heated at 1 atm to induce bubble nucleation and track bubble growth and movement. In contrast to previous studies on natural and experimentally produced samples, we found that bubbles readily nucleated on plagioclase and clinopyroxene crystals, that their contact angle changes during growth and that they can grow to sizes many times that of the silicate on whose surface they originated. The rapid heterogeneous nucleation of bubbles at low degrees of supersaturation in the presence of silicate crystals demonstrates that silicates can affect when vesiculation ensues, influencing subsequent permeability development and effusive vs. explosive transition in volcanic eruptions

Rugby Union football in the land of the Wallabies, 1874-1949: same game, different ethos

Football as a generic game-form was a feature of the sporting culture of the settlers of Australia. As the various codes emerged in Britain they were 'exported' to the colonies throughout the Empire. In Australia this cultural imposition was not complete for the British games faced significant cultural resistance, most notably from Australian Rules football. The first formal club was founded circa 1865 and by the time a governing body was formed in 1874, the game had acquired distinctive playing and administrative traits and a sporting ethos, These were aberrant to the British form as pragmatic modifications were made in response to the social, cultural and environmental exigencies and demands of the frontier-like context: the game of Rugby immediately became Australianized. This analysis traces the development of the game's culture in Australia through the initial 75 years of its institutionalization and demonstrates that despite its transit through the colonial era, urbanization, nationalism, federation and the travails of two World Wars, aspects of the residual culture remained. Rugby football, established in NSW and Queensland as a feature of the cultural hegemony of British Imperialism, prevailed largely unchanged in terms of power relations, ideology, finances and success over its first 75 years. This discussion reflects upon the critical influences, incidents and individuals that impacted upon and shaped Rugby union football in NSW and Queensland up to the founding of the Australian Rugby Football Union, which took until 1949 to occur