John Browning, BSc, MSc, PhD

Assistant Professor

Bubble growth in Rhyolite 

Bubble growth dynamics exert a primary control on the explosivity of volcanic bombs, but complex nucleation and growth dynamics remain poorly understood. Vesiculation that occurs post-fragmentation in rhyolitic pumice clasts and bombs as they travel along a ballistic cooling trajectory can lead to misleading interpretation of final end-member vesicularities. We have used hot-stage microscopy to directly observe vesiculation of a Chaitén rhyolite melt (containing ~0.95 wt. % H2O) at atmospheric pressure and magmatic temperatures.

Cone growth at Etna volcano, Italy using Long range laser scanning

During volcanic eruptions, measurements of the rate at which magma is erupted underpin hazard assessments. For eruptions dominated by the effusion of lava, estimates are often made using satellite data; here, in a case study at Mount Etna (Sicily), we make the first measurements based on terrestrial laser scanning (TLS), and we also include explosive products. During the study period (17–21 July 2012), regular Strombolian explosions were occurring within the Bocca Nuova crater, producing a ~50 m-high scoria cone and a small lava flow field. TLS surveys over multi-day intervals determined a mean cone growth rate (effusive and explosive products) of ~0.24 m3·s−1.