Paul A. Ashwell

• PhD in Geology
• Professor (Assistant) at University of Toronto

Fieldtrips are often seen as a crucial learning experience for undergraduate students. In the field, students are able to put into practice knowledge and skills previously learned in order to experience similar scenarios to those they may encounter in a career. However, fieldtrips are also a stressful experience, requiring students to work long hou...

The highly transient nature of outgassing commonly observed at volcanoes is in part controlled by the permeability of lava domes and shallow conduits. Lava domes generally consist of a porous outer carapace surrounding a denser lava core with internal shear zones of variable porosity. Here, we examine densification using uniaxial compression experi...

The eruption of large, rhyolitic lava domes is commonly accompanied by the production of block and ash flows, sourced from collapse of part of the dome. Eruption rate, lava dome structure, vent morphology, topography and the properties of the lava (e.g. crystallinity) all contribute to the likelihood of collapse. Here we present the initial finding...

Silica-oversaturated, alkaline igneous complexes represent unusual magmas that are frequently enriched in rare earth elements (REEs) and high field strength elements. This often makes them a prospecting target for economic mineralisation of these unique metals, for which demand is exponentially increasing in the renewable energy, military and advan...

A Correction to this paper has been published: https://doi.org/10.1007/s00445-021-01441-8

Understanding the processes that drive explosive-effusive transitions during large silicic eruptions is crucial to hazard mitigation. Conduit models usually treat magma ascent and degassing as a gradual, unidirectional progression from bubble nucleation through magmatic fragmentation. However, there is growing evidence for the importance of bi-dire...

The French Creek Granite, New Zealand, is an alkaline intrusion with enrichment in rare earth elements (REE). Petrography and whole-rock geochemical signatures demonstrate that the c. 82–84-Ma French Creek Granite is a composite granitoid, dominated by a ferroan, weakly peraluminous biotite alkali feldspar granite to syenogranite, with subordinate...

Field trips are one of the most critical pieces of learning for students in sciences like geology, biology, and geography. Virtual field trips (VFT) are being increasingly considered as sophisticated and effective forms of teaching, especially with the rise of new technologies and the growing demand for more inclusive classroom environments. This r...

The eruption of large, rhyolitic lava domes may be accompanied by the formation of large block and ash flows. This may be linked to the style of dome extrusion—whether it forms a series of individual lobes, flows or spines (exogenous) or grows by internal inflation (endogenous). Lava domes can transition from one extrusive style to another as a res...

As a recent hire in the position of Senior Tutor in geology, my focus is both on lab and field based teaching. In particular this is guided by an overarching goal of linking the introductory 100 level courses (open to students of any background) to 200 level courses (only geology majors). Here I will present my first impressions of teaching at thes...

Near-surface basaltic dykes may become unstable when buoyancy and overpressure are not maintained and solidification not fully accomplished. Additionally temporal variation of the dyke geometry such as widening may further compromise stability and induce draining. A 5-10 m wide, variably dipping basaltic-andesite dyke in the wall of Red Crater, New...

Lava dome stability is reliant on pore pressure, which varies according to the evolution of the permeable porous network. Here, we present experimental results of porosity and permeability evolution during compaction of aphiric (from Ngongotaha volcano) and crystal-bearing (from Tarawera volcano) pumiceous, rhyolitic lavas from Taupo Volcanic Zone,...

The evolution of the porous network during lava dome extrusions is commonly perceived as the key control on the permeability which regulates the pore pressure, thereby challenging the stability of the dome. Here, we present experimental results of porosity and permeability evolution during compaction of aphiric and crystal-bearing rhyolitic, pumice...

Shearing and faulting at active volcanoes may differ to tectonic faulting due to their distinct temperature conditions above those of the Earth's geotherm. In particular, the ascent of high-viscosity magma/rocks in upper conduits leads to shear/fault zones, with/without gouge formation and sometimes frictional melting; yet, details of the deformati...

During spherulite growth water enrichment occurs in the surrounding glass, but generally it is not assumed to play an important role in volcanic activity. Our new data on the influence of spherulite growth on the surrounding glass illustrates the magnitude and spatial distribution of water enrichment through cracks that accompany spherulite growth....

Technological advances now allow experimental volcanology at magmatic temperatures and pressures. We have designed an internally heated pressure vessel that allows 25mm by 50mm cylindrical samples to be heated to 1000oC in a steam atmosphere up to 100MPa. A sliding magnetic mechanism allows quenching of the sample and a external pressurization devi...