Deducing the Fluid Dynamical Behaviour of Ancient Magma Bodies

The fluid dynamical behaviour of magma, either when it is trapped in the crust, or erupted at the Earth’s surface, plays a fundamental role in determining Earth evolution. For the most part, however, it is not possible to directly observe whether or not magma bodies in the crust convec, or whether they are entirely static during cooling and crystallisation. In this talk I will show how information about the fluid dynamical behaviour of ancient, now fully solidified, bodies of basalt can be extracted from careful observation both on the outcrop scale (1-100m) and on the grain-scale (<1mm). I will talk about large-scale processes inferred to have occurred in the km-scale Skaergaard Intrusion of East Greenland, and also about the fingerprint of convection preserved in small-scale spatial variations of composition and microstructure in sills and dykes (tabular intrusions that commonly act as conduits feeding surface eruptions). Link to join the YouTube live stream: https://youtu.be/p4EFP0VvsGw