Cara Wells, Postgraduate Researcher

Melt Fragmentation in Giant Impact Events: a Volcanological Approach

Contact DetailsCara Wells

Project Overview

Giant meteorite impacts have occurred throughout the history of Earth and are fundamental in all planetary evolution. These impacts form craters 10 to > 100 km across and in doing so melt the target rocks depositing regional ejecta blankets and global fallout layers. These proximal and distal ejecta layers can provide valuable sources of information about the physical processes that occur during terrestrial impacts.

Melt bearing impact deposits, known as “suevite”, are found both as a fill within the craters and as outflow sheets. Despite decades of research there is little consensus within the scientific community as to the formation of suevite with interpretations ranging from a granular-fluid-based density current to a fall out deposit. These deposits contain clasts of the target lithologies, shocked mineral phases, and fragments of chilled impact melt that range in size from <50 μm to >100mm.

This PhD project will focus in on these melt fragments within the suevite and use volcanological techniques employed to study explosive volcanic eruptions to gain a further understanding of the fragmentation processes during giant impact events. Using both SEM analysis and optical microscopy, images of the melt fragments will be generated and subsequent image analysis will quantify the range of shapes and vesicularities. With these measurements it should allow a comparison of impact melt morphology to pyroclasts from explosive eruptions to provide analogies for impact melt formation. This project aims to advance our understanding of the processes occurring during a meteorite impact, with an initial focus on Ries crater, Germany, and develop a method to allow comparisons to be made, not only to volcanic eruptions but across different craters of varying sizes and compositions.  This research will shed a new light on the fragmentation processes during impacts and provide further data to aid in constraining existing impact models.

Research Theme

Solid Earth

Research Questions

  • Can methods used to study pyroclasts from explosive volcanic eruptions be adapted for the study of impact melt fragments?
  • Can a comparison of shard shapes between impact melt fragments and volcanic pyroclasts provide an analogy to fragmentation in impact events?
  • Does fragmentation differ across impact sites where there are differences in composition and size?

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