Tue 27 Feb 12:00: The TTG window and the formation of Earth’s earliest continental crust.
A large number of papers have been written on the processes responsible for the formation of the Earth’s earliest continental crust. These range from plume-based processes, through modern style plate tectonics all the way through to formation from bombardment as the solar system passed through galactic regions with high impact potential. Simultaneously, numerous papers have Attempted to identify the melting sources for the magnetic suites that define early continental crust, The Trondjhemite- Tonalite-Granodiorite suite. Despite the progress in these studies there remains considerable disagreement on sources and processes for TTG generation – in part because of a tendency to try and identify a single process and a single source for all the earliest fragments of continental crust. In this talk I will discuss a number of these issues and, in particular, whether or not a single source and single process is a geologically sensible approach, arguing instead that a number of different processes may operate and may independently form crust that is sufficiently thick and buoyant as to be preservable in the geological record.
- Speaker: Richard White, School of Earth and Environmental Sciences, University of St Andrews
- Tuesday 27 February 2024, 12:00-13:00
- Venue: Department of Earth Sciences, Tilley Lecture Theatre.
- Series: Department of Earth Sciences Seminars (downtown); organiser: Dr Rachael Rhodes.
Tue 27 Feb 12:00: The TTG window and the formation of Earth’s earliest continental crust.
A large number of papers have been written on the processes responsible for the formation of the Earth’s earliest continental crust. These range from plume-based processes, through modern style plate tectonics all the way through to formation from bombardment as the solar system passed through galactic regions with high impact potential. Simultaneously, numerous papers have Attempted to identify the melting sources for the magnetic suites that define early continental crust, The Trondjhemite- Tonalite-Granodiorite suite. Despite the progress in these studies there remains considerable disagreement on sources and processes for TTG generation – in part because of a tendency to try and identify a single process and a single source for all the earliest fragments of continental crust. In this talk I will discuss a number of these issues and, in particular, whether or not a single source and single process is a geologically sensible approach, arguing instead that a number of different processes may operate and may independently form crust that is sufficiently thick and buoyant as to be preservable in the geological record.
- Speaker: Richard White, School of Earth and Environmental Sciences, University of St Andrews
- Tuesday 27 February 2024, 12:00-13:00
- Venue: Department of Earth Sciences, Tilley Lecture Theatre.
- Series: Department of Earth Sciences Seminars (downtown); organiser: Dr Rachael Rhodes.
Thu 01 Feb 11:30: Transport and Settling of Buoyant Microplastics in Turbidity Currents
Although tens of millions of tons of plastic waste are released into the ocean each year, less than 300 kilotons remain on or near the ocean surface. This is particularly puzzling because more than half of plastics that are produced are buoyant in sea water. One mechanism that can result in buoyant plastic settling is the process of biofouling in which microbes and other organic material can accumulate on the plastics rendering them more dense. Less studied is the accumulation of inorganic material on the plastics. For example, clay has recently been shown to attach to plastics, particularly in the presence of surfactants. Here we report on laboratory experiments showing that plastic particles which are less dense than fresh water can settle due to the accumulation of glass spheres (“sand”) on their surface. This process is shown to occur dynamically as sand and plastic particles mix turbulently during the impulsive release of a turbidity current, which can carry some of the plastic particles to depth along with the settling sand. [This work reports on experiments performed by Woods Hole Oceanographic Institute (WHOI) Geophysical Fluid Dynamics (GFD) Fellow Quentin Kriaa during the WHOI GFD Summer Program 2023, co-supervised by Claudia Cenedese and Jim McElwaine.]
- Speaker: Professor Bruce Sutherland, Uni of Alberta
- Thursday 01 February 2024, 11:30-12:30
- Venue: Open Plan Area, Institute for Energy and Environmental Flows, Madingley Rise CB3 0EZ.
- Series: Institute for Energy and Environmental Flows (IEEF); organiser: Catherine Pearson.
Thu 01 Feb 11:30: Transport and Settling of Buoyant Microplastics in Turbidity Currents
Although tens of millions of tons of plastic waste are released into the ocean each year, less than 300 kilotons remain on or near the ocean surface. This is particularly puzzling because more than half of plastics that are produced are buoyant in sea water. One mechanism that can result in buoyant plastic settling is the process of biofouling in which microbes and other organic material can accumulate on the plastics rendering them more dense. Less studied is the accumulation of inorganic material on the plastics. For example, clay has recently been shown to attach to plastics, particularly in the presence of surfactants. Here we report on laboratory experiments showing that plastic particles which are less dense than fresh water can settle due to the accumulation of glass spheres (“sand”) on their surface. This process is shown to occur dynamically as sand and plastic particles mix turbulently during the impulsive release of a turbidity current, which can carry some of the plastic particles to depth along with the settling sand. [This work reports on experiments performed by Woods Hole Oceanographic Institute (WHOI) Geophysical Fluid Dynamics (GFD) Fellow Quentin Kriaa during the WHOI GFD Summer Program 2023, co-supervised by Claudia Cenedese and Jim McElwaine.]
- Speaker: Professor Bruce Sutherland, Uni of Alberta
- Thursday 01 February 2024, 11:30-12:30
- Venue: Open Plan Area, Institute for Energy and Environmental Flows, Madingley Rise CB3 0EZ.
- Series: Institute for Energy and Environmental Flows (IEEF); organiser: Catherine Pearson.