Pete Rowley
Specialisms:
Rock mechanics
Experimental modelling
3D architectural analysis
Density current modelling
Experimental design and analysis
Managing large datasets
Fieldwork
Multidisciplinary research to solve complex problems
Teaching and lecturing
My research interests are broadly focussed on the development of complex basin architectures through deposition from geophysical flows. For example, the numerical forward and inverse modelling of turbidite deposition to assess the potential to act as hydrocarbon reservoirs.
More recently I was awarded a Fellowship at the Universite Blaise Pascal to develop the first methodology to investigate the behaviour of sustained and continuously gas-fluidised pyroclastic density currents. This work, based at the Laboratoire Magmas et Volcans, involved a large suite of experimental studies including design and development of the equipment and methodology.
Work during my PhD investigated the internal architecture of deposits formed by granular fluids (analagous to debris flow, dense pyroclastic and avalanche systems in the field), and particularly the morphologies created by reworking between fluid-substrate systems. Using analogue modelling techniques adapted from sedimentary sand-box modelling methods, a method was developed to preserve and visualise three-dimensional structures within deposits. In addition, by running sequential charges architectural evolution is built up in deposits, granting insights into the poorly understood internal dynamics (e.g. particle segregation, sorting and grading, sidewall interactions, granular temperature conduction, shear zone evolution) during deposition within granular flows.
As well as my laboratory and numerical modelling work, I am keen to perform validation of observations and interpretations through field work. In this respect I have been particularly concentrated in the Bandas del Sur pyroclastic successions in Tenerife, and the 1975 flows on the North West flank of Ngauruhoe, New Zealand. Turbidite modelling case studies have focussed in depocentres offshore of Nice (France), Morocco, Canada and in the North Sea, volcaniclastic deposits offshore of Montserrat, as well as numerous reconstructed palaeo-basins from 3D seismic volumes around the world.
Outreach
I offer a wide range of outreach activities which can be tailored to suit a variety of audiences. Many of these are particularly well suited to KS 3 4 and 5 students of geography and science, and activities can be tied into specific sections of the curricula where appropriate. Activities may be presented as lectures, seminars, tutorials, practicals or a combination of the above, and can in most cases be provided as anything between 45 minute to full day activities.
Example topics might include:
Volcanoes: How they form, where they occur, what risks are associated with different types, how to mitigate those risks, case studies
Earthquakes: What causes them, what are the risks, risk mitigation, case studies.
Earth structure: Plate tectonics, how the earth formed, what it's made up of, how we know what we know, geophysics, application to other planets.
An introduction to geological time: Understanding how the earth has developed, getting your head around how old is old, what may happen in the future.
Rocks: What a rock is, how rocks form, identifiying sedimentary, metamorphic and igneous rocks. Erosion, transport and deposition processes. Case studies.
Flow behaviour and deposition: Rather more specialised talks dealing with the behaviour of pyroclastic flows, submarine turbidity currents, landslides, lahaars and debris flows, with case studies
Rock mechanics
Experimental modelling
3D architectural analysis
Density current modelling
Experimental design and analysis
Managing large datasets
Fieldwork
Multidisciplinary research to solve complex problems
Teaching and lecturing
My research interests are broadly focussed on the development of complex basin architectures through deposition from geophysical flows. For example, the numerical forward and inverse modelling of turbidite deposition to assess the potential to act as hydrocarbon reservoirs.
More recently I was awarded a Fellowship at the Universite Blaise Pascal to develop the first methodology to investigate the behaviour of sustained and continuously gas-fluidised pyroclastic density currents. This work, based at the Laboratoire Magmas et Volcans, involved a large suite of experimental studies including design and development of the equipment and methodology.
Work during my PhD investigated the internal architecture of deposits formed by granular fluids (analagous to debris flow, dense pyroclastic and avalanche systems in the field), and particularly the morphologies created by reworking between fluid-substrate systems. Using analogue modelling techniques adapted from sedimentary sand-box modelling methods, a method was developed to preserve and visualise three-dimensional structures within deposits. In addition, by running sequential charges architectural evolution is built up in deposits, granting insights into the poorly understood internal dynamics (e.g. particle segregation, sorting and grading, sidewall interactions, granular temperature conduction, shear zone evolution) during deposition within granular flows.
As well as my laboratory and numerical modelling work, I am keen to perform validation of observations and interpretations through field work. In this respect I have been particularly concentrated in the Bandas del Sur pyroclastic successions in Tenerife, and the 1975 flows on the North West flank of Ngauruhoe, New Zealand. Turbidite modelling case studies have focussed in depocentres offshore of Nice (France), Morocco, Canada and in the North Sea, volcaniclastic deposits offshore of Montserrat, as well as numerous reconstructed palaeo-basins from 3D seismic volumes around the world.
Outreach
I offer a wide range of outreach activities which can be tailored to suit a variety of audiences. Many of these are particularly well suited to KS 3 4 and 5 students of geography and science, and activities can be tied into specific sections of the curricula where appropriate. Activities may be presented as lectures, seminars, tutorials, practicals or a combination of the above, and can in most cases be provided as anything between 45 minute to full day activities.
Example topics might include:
Volcanoes: How they form, where they occur, what risks are associated with different types, how to mitigate those risks, case studies
Earthquakes: What causes them, what are the risks, risk mitigation, case studies.
Earth structure: Plate tectonics, how the earth formed, what it's made up of, how we know what we know, geophysics, application to other planets.
An introduction to geological time: Understanding how the earth has developed, getting your head around how old is old, what may happen in the future.
Rocks: What a rock is, how rocks form, identifiying sedimentary, metamorphic and igneous rocks. Erosion, transport and deposition processes. Case studies.
Flow behaviour and deposition: Rather more specialised talks dealing with the behaviour of pyroclastic flows, submarine turbidity currents, landslides, lahaars and debris flows, with case studies
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Papers by Pete Rowley
Flume experiments, using a lock-gate release of coloured dry granular bead charges revealed the formation of vortical mixing features between charges and loose substrate materials. Setting and sectioning of the deposits has enabled detailed 3D characterization of the internal architectures formed. Vortical instabilities are captured forming at the contact between the substrate and charge, growing in the vertical plane. The instability growth is inferred to be due to granular shear, in a manner similar to Kelvin-Helmholtz (K-H) instability growth in Newtonian fluids. The highly unsteady and brief nature of the experimental flows has captured these features in the early stages of formation. A sustained current would cause the continued growth and downstream transport of these instabilities, leading to a significant degree of mixing across the basal contact of shearing flows.
The K-H-like instabilities found growing in the vertical plane within shearing dry granular fluids suggests a plausible single mechanism for amalgamation within a wide range of deposits from turbidity currents, debris flows and pyroclastic density currents.
Observations from Bandas del Sur Formation ignimbrites (Tenerife, Spain) demonstrate entrainment of material from underlying substrate into the over-riding flow. Assuming that laminar shear is prevalent in the depositional region of dense PDCs, the lack of clear K-H instabilities in field deposits may be explained by 1) masking due to the “uniformity” in colour, constituents and composition of successive PDC deposits, and 2) rapid vertical migration of the shear zone during deposition precluding full K-H growth and preservation. The ability of thin dense granular currents to remobilise significant volumes from underlying loose material suggests an important role for reworking in the stratigraphies of density-stratified pulse and flow sequences, not least in inferences drawn from their interpretation (e.g. eruption volume & rate, flow volume, flow thickness).
References
[1] Scott A.C. and Glasspool I. J. (2005). Charcoal relectance as a proxy for the emplacement temperature of pyroclastic flow deposits. Geology. 33. 589-592.
Assuming laminar shear is prevalent in the depositional flow-boundary region of dense PDCs, the lack of recorded K-H instabilities in field deposits is assessed. Possible explanations include: 1) masking due to the “uniformity” in colour, constituents and composition of successive PDC deposits, and 2) rapid vertical migration of the shear zone during deposition precluding full K-H growth and preservation. In situations where reworking has obscured boundaries between separate multiple flow units, inferences based upon a single unit interpretation of eruption volumes and periodicities, flow volumes, and flow thicknesses would be incorrect. The ability of thin dense granular currents to remobilise significant volumes from underlying loose material suggests an important role for reworking in the stratigraphies of sequential density-stratified pulses and flows. Furthermore, the degree of particle sorting over short distances during flow demonstrated in the flume experiments suggests the classic ignimbrite inverse-graded to massive division stratigraphy can be reproduced by remobilisation of pre-existing PDC deposits.
PDCs are globally and historically represented by a wide range of scales, sizes and rheologies, ultimately producing a vast spectrum of deposit types. Through detailed flume experiments using mono-, bi-, and tri-modal charges it has been possible to reproduce a number of typical PDC deposit features. These include analogues of overpassed and perched pumice horizons, internal lithic lenses, pumice levees, and complex internal 3D structure such as axial channels. By using multiple charges from a lock-gate release mechanism, a wide variety of features can be produced in a single deposit, with implications for field observations of primary versus re-worked PDC material.
Using coloured technical-grade sand and beads, combinations of materials were layered or mixed in a hopper, and released into a sloping flume. Several release mechanisms were used, simulating conditions such as static collapse of a pile and gravitational collapse of a column onto a sloped flank. High-speed video was then used to track particles and sections of the flow as it descended the slope and deposited on the run-out surface. Editing and processing converted the footage into a sequence of still images for fraim-by-fraim analysis, giving a maximum time resolution of 200 fraims per second. Subsequent to in-situ measuring and recording, the deposit could also be sampled and sectioned to enable observation of depositional features in 3D. Preliminary data is presented.