Project overview: The eruption of low viscosity magmas (≲ 1,000 Pa s) is the most frequent and volumetrically abundant form of volcanism on Earth and on other planets and satellites. Explosive eruption of these magmas (i.e. episodes or events that produce fragments termed pyroclasts) commonly occurs by lava fountaining and is indicative of magmas spanning a wide range of melt compositions including komatiite, basalt, alkaline mafic melts and carbonatite. Fountains show a great diversity in height and are typically 100’s m but can reach heights of ~1 km.
During fountaining, hot pyroclasts, originally formed by fluid dynamic induced breakup of the parent magma, are cooled by forced convection and radiative heat loss. Depending on the efficiency of cooling with respect to other timescales (e.g., transport, relaxation), a wide array of deposit textures can be formed. Clasts may be deposited hot, above their glass transition temperature, forming spatter mounds, ramparts and potentially rheomorphic lava flows. In contrast, clasts may be deposited cold, producing tephra cones and laterally extensive tephra blankets. Thus, the deposit type and clast textures formed can ‘forensically’ provide information about the fountain dynamics and the physical properties of the melt.
Overall PhD project aim: To combine analogue experiments, textural study of natural pyroclasts and thermal modelling to produce a framework that allows the textural properties of pyroclasts (e.g. shape, size) to ‘forensically’ reveal the internal dynamics (e.g. temperature, velocity) of the parent lava fountain.
(1) Analogue experiments. Scaled laboratory experiments on analogue materials offer a way to systematically isolate variables and observe and quantify volcanologically relevant processes. In this PhD, at UoL, a controlled gas/air flow will be fed into a column of analogue magma. The gas flux will be systemically varied, and high-speed videography will identify when magma disruption/fragmentation occurs. In the cases where fragmentation is successful the high-speed images will document the droplet (i.e. analogue pyroclast) size distribution produced.
(2) Thermal modelling. Building on Lin’s existing modelling infrastructure at NTHU, commonly used to address heat transfer problems in turbulent flows, a pyroclast cooling model that accounts for non-spherical morphologies will be developed. This will yield a characteristic cooling time for irregular shaped pyroclasts of various sizes (informed by the analogue experiments) –key information that will allow for ‘forensic’ interpretation of deposits.
(3) Textural analysis of natural samples. Close to the NTHU campus lies the active Tatun Volcanic Group. Of particular interest here is Mt. Hunglu – a basaltic volcano with a range of lava fountain deposits. Jones and the PhD student will travel to Mt. Hunglu to study these deposits in the field. Samples from the deposits will be texturally analysed at UoL to uncover their thermal history.
Studentship information: This project is part of a 4-year Dual PhD degree programme between the National Tsing Hua University (NTHU) in Taiwan and the University of Liverpool (UoL) in England. As Part of the NTHU-UoL Dual PhD Award students are in the unique position of being able to gain 2 PhD awards at the end of their degree from two internationally recognised world leading universities. As well as benefiting from a rich cultural experience, students can draw on large scale national facilities of both countries and create a worldwide network of contacts across two continents.
To apply for this opportunity, please visit: https://www.liverpool.ac.uk/study/postgraduate-research/how-to-apply/ When applying through the UoL website please ensure you quote the supervisor (Dr Jones) & project title you wish to apply for and note ‘NTHU-UoL Dual Scholarship’ when asked for details of how plan to finance your studies.
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