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A technical user manual for volcanic ash dispersion modelling using python-FALL3D.

Recently acquired seismic reflection and gravity potential field data was used to investigate the distribution of volcanic facies and large scale structural architecture of the Mentelle Basin, located on the southwestern margin of Australia. Isochron and seismic facies maps were used to identify the thickness and distribution of volcanic facies. These maps show that volcanism is generally confined to the Western Mentelle Basin, with two distinct areas of thick volcanic deposits occurring to the centre and north of the area. Two and three dimensional gravity forward models were created in IGMAS+. Two dimensional gravity modelling shows that the crust is extremely thin in the Western Mentelle (c.10km), associated with two mantle highs observed to the north and centre of the Western Mentelle. The crust thickens from the Eastern Mentelle (>20km) towards mainland Australia and the Naturaliste Plateau. The two modelled mantle highs coincide with the two seismically defined areas of thick volcanic deposits. Analogue models indicate that rift related volcanism is generally confined to the locus of extension where the pressure is lowest. Thus results of gravity modelling and seismic interpretation in this study indicate that Jurassic - Cretaceous extension was focussed in the Western Mentelle. This conclusion conforms to models of rift related basin formation, where the flanks of the basin are uplifted; an angular unconformity in the Eastern Mentelle may support the occurrence of rift-flank uplift in this area as a result of asthenospheric rise and rifting while the deposition of volcanic material was focussed in the Western Mentelle.

The Asia-Pacific region is home to well over half the world's population and is also the focus of some of earth's most intense geological activity. It is no surprise therefore that geological hazards, in particular earthquake and volcano hazards, make the Asia-Pacific region the scene of som e of the worlds most lethal natural disasters. While this is evident form a perusal of historical data relating to natural disasters, it is not clear how well such historical data can be used as a guide for high -impact events that might be expected in the future. This uncertainty is due to (1) how poorly extreme geological events having long recurrence intervals are represented in the relatively short historical record, and (2) the failure of the historical record to account for recent demographic trends, in particular the explosive growth of population in the Asia -Pacific region and its rapid urbanisation during the 20 th century. We present here two novel techniques for assessing the potential impacts of volcanic and earthquake events on human population in the Asia Pacific region. For volcanic risk, we have calculated the frequency of large eruptions, aggregated for the countries of the Asia -Pacific region, using data provided by the Smithsonian Institution's Global Volcanism Program. These eruption frequ encies have been combined with an analysis of population data for the region to estimate the average number of people who might be affected, in the broad sense of death, injury or loss of essential services, by a major volcanic eruption. For earthquake, risk, we have considered that the potential future high -impact events will be driven by the probability that an earthquake might occur in or adjacent to one of the many megacities of the Asia -Pacific region. Earthquake probabilities near megacities are cal culated from catalogue data, and these are combined with a rough criterion for damage based on earthquake ground motion, to asses potentially affected populations. We present preliminary results of these analyses, which suggest the potential for earthquakes and volcanoes in the Asia-Pacific region to cause future `mega-disasters', for which affected populations may be much larger than the numbers indicated by the historical record.

This booklet identifies different types of volcanoes, and the dangers associated when volcanic materials are ejected in an eruption. It explains the importance of why we should study volcanoes and the effects these eruptions have on the atmosphere and climate. It also identifies where volcanoes are located in Australia. Student activities are included.