Wed 13 Mar 16:00: TBC
TBC
- Speaker: Victoria Fernandes, GFZ Potsdam
- Wednesday 13 March 2024, 16:00-17:00
- Venue: Wolfson Lecture Theatre.
- Series: Bullard Laboratories Wednesday Seminars; organiser: Megan Holdt.
Wed 13 Mar 16:00: TBC
TBC
- Speaker: Victoria Fernandes, GFZ Potsdam
- Wednesday 13 March 2024, 16:00-17:00
- Venue: Wolfson Lecture Theatre.
- Series: Bullard Laboratories Wednesday Seminars; organiser: Megan Holdt.
Wed 28 Feb 16:00: The Tristan da Cunha mantle plume, new insights from geophysical, petrological and geochemical studies along the Walvis Ridge hotspot track and at Tristan da Cunha Island
Tristan da Cunha is a hotspot in the South Atlantic Ocean, located 450 km east of the Mid-Atlantic Ridge. The intraplate volcanoes and seamounts that form the Tristan da Cunha archipelago are connected to the Cretaceous (132 Ma) Etendeka continental flood basalt province in Namibia via the aseismic Walvis Ridge. The ridge is built-up by seamounts chains and submarine volcanic plateaus that show a clear age progression and extend from the Namibian continental margin (northeast) to the volcanic islands of Tristan da Cunha and Gough (southwest). This age-progressive distribution of volcanic rock samples collected from the Walvis Ridge and the Rio Grande Rise west of the Mid-Atlantic Ridge provide evidence for the volcanism at Tristan da Cunha and the formation of Cretaceous flood basalts in Namibia and Brazil to be due to a common hotspot source, with the Walvis Ridge and the Rio Grande Rise documenting the hotspot tracks. The Tristan da Cunha-Walvis Ridge system is one of the few examples of a complete hotspot track, and thus the it is generally assumed to be a surface expression of a long-lasting mantle plume. However, a debate continues about whether the mantle plume beneath Tristan da Cunha is an expression of convection of the whole mantle or of shallower plate-driven convection. NW Namibia, the Walvis Ridge, Tristan da Cunha, and the South Atlantic Ocean in general were target regions for various international geophysical and geochemical projects over the past two decades, including a recent IODP expedition to the Walvis Ridge. In my talk, I will summarize the recent findings with a special focus to the crust and upper mantle structure beneath the region around Tristan da Cunha.
- Speaker: Wolfram Geissler, Alfred Wegener Institute
- Wednesday 28 February 2024, 16:00-17:00
- Venue: Wolfson Lecture Theatre.
- Series: Bullard Laboratories Wednesday Seminars; organiser: Megan Holdt.
Wed 28 Feb 16:00: The Tristan da Cunha mantle plume, new insights from geophysical, petrological and geochemical studies along the Walvis Ridge hotspot track and at Tristan da Cunha Island
Tristan da Cunha is a hotspot in the South Atlantic Ocean, located 450 km east of the Mid-Atlantic Ridge. The intraplate volcanoes and seamounts that form the Tristan da Cunha archipelago are connected to the Cretaceous (132 Ma) Etendeka continental flood basalt province in Namibia via the aseismic Walvis Ridge. The ridge is built-up by seamounts chains and submarine volcanic plateaus that show a clear age progression and extend from the Namibian continental margin (northeast) to the volcanic islands of Tristan da Cunha and Gough (southwest). This age-progressive distribution of volcanic rock samples collected from the Walvis Ridge and the Rio Grande Rise west of the Mid-Atlantic Ridge provide evidence for the volcanism at Tristan da Cunha and the formation of Cretaceous flood basalts in Namibia and Brazil to be due to a common hotspot source, with the Walvis Ridge and the Rio Grande Rise documenting the hotspot tracks. The Tristan da Cunha-Walvis Ridge system is one of the few examples of a complete hotspot track, and thus the it is generally assumed to be a surface expression of a long-lasting mantle plume. However, a debate continues about whether the mantle plume beneath Tristan da Cunha is an expression of convection of the whole mantle or of shallower plate-driven convection. NW Namibia, the Walvis Ridge, Tristan da Cunha, and the South Atlantic Ocean in general were target regions for various international geophysical and geochemical projects over the past two decades, including a recent IODP expedition to the Walvis Ridge. In my talk, I will summarize the recent findings with a special focus to the crust and upper mantle structure beneath the region around Tristan da Cunha.
- Speaker: Wolfram Geissler, Alfred Wegener Institute
- Wednesday 28 February 2024, 16:00-17:00
- Venue: Wolfson Lecture Theatre.
- Series: Bullard Laboratories Wednesday Seminars; organiser: Megan Holdt.
Wed 21 Feb 16:00: The Turkana Rift Arrays Investigating Lithospheric Structure (TRAILS) Experiment
The Turkana Depression is a broad ( 500km-wide), topographically-subdued ( 0.5km), region between the elevated Ethiopian ( 1.5km) and East African Plateaus ( 2.5km). The Depression is unique in East Africa for being host to a NW-SE-trending failed Mesozoic (Anza) rift system through which the near-orthogonal, N-S-trending East African Rift subsequently developed. Whether the Depression’s low-lying nature is a result of a significantly thinned crust instigated by its multiple rifting phases, or instead due to a lack of dynamic mantle support is debated. Also poorly understood is the extent to which Cenozoic rifting and magmatism have developed across the Depression during the linkage of other comparatively narrow East African Rift zones to the north and south. Utilising data from the 2019-2021 Turkana Rift Arrays Investigating Lithospheric Structure project and surrounding networks, receiver function analysis and its joint inversion with surface-waves2, are used to probe Moho architecture and the lithosphere-asthenosphere system. Receiver function results1 reveal a thinned crust (20-25km) throughout the Depression: 10-20km thinner than the Ethiopian Plateau and Tanzania Craton. The Depression’s low elevations are thus likely an isostatic response from a thinned crust and not a lack of mantle dynamic support. High associated crustal stretching factors (β
1. Ogden, C. et al., (2023), Earth Planet. Sci. Lett., 609, 118,088, doi:10.1016/j.epsl.2023.118088. 2. Kounoudis, R. et al., (2023), Earth Planet. Sci. Lett., doi:10.1016/j.epsl.2023.118386. 3. Boyce, A., et al., (2023), Geochem. Geophys. Geosyst., 24 (8), e2022GC010,775, doi:10.1029/2022GC010775.
- Speaker: Ian Bastow, Imperial College London
- Wednesday 21 February 2024, 16:00-17:00
- Venue: Wolfson Lecture Theatre.
- Series: Bullard Laboratories Wednesday Seminars; organiser: Megan Holdt.
Wed 21 Feb 16:00: The Turkana Rift Arrays Investigating Lithospheric Structure (TRAILS) Experiment
The Turkana Depression is a broad ( 500km-wide), topographically-subdued ( 0.5km), region between the elevated Ethiopian ( 1.5km) and East African Plateaus ( 2.5km). The Depression is unique in East Africa for being host to a NW-SE-trending failed Mesozoic (Anza) rift system through which the near-orthogonal, N-S-trending East African Rift subsequently developed. Whether the Depression’s low-lying nature is a result of a significantly thinned crust instigated by its multiple rifting phases, or instead due to a lack of dynamic mantle support is debated. Also poorly understood is the extent to which Cenozoic rifting and magmatism have developed across the Depression during the linkage of other comparatively narrow East African Rift zones to the north and south. Utilising data from the 2019-2021 Turkana Rift Arrays Investigating Lithospheric Structure project and surrounding networks, receiver function analysis and its joint inversion with surface-waves2, are used to probe Moho architecture and the lithosphere-asthenosphere system. Receiver function results1 reveal a thinned crust (20-25km) throughout the Depression: 10-20km thinner than the Ethiopian Plateau and Tanzania Craton. The Depression’s low elevations are thus likely an isostatic response from a thinned crust and not a lack of mantle dynamic support. High associated crustal stretching factors (β
1. Ogden, C. et al., (2023), Earth Planet. Sci. Lett., 609, 118,088, doi:10.1016/j.epsl.2023.118088. 2. Kounoudis, R. et al., (2023), Earth Planet. Sci. Lett., doi:10.1016/j.epsl.2023.118386. 3. Boyce, A., et al., (2023), Geochem. Geophys. Geosyst., 24 (8), e2022GC010,775, doi:10.1029/2022GC010775.
- Speaker: Ian Bastow, Imperial College London
- Wednesday 21 February 2024, 16:00-17:00
- Venue: Wolfson Lecture Theatre.
- Series: Bullard Laboratories Wednesday Seminars; organiser: Megan Holdt.
Wed 31 Jan 16:00: TBC
TBC
- Speaker: Max Van Wyk de Vries, University of Cambridge
- Wednesday 31 January 2024, 16:00-17:00
- Venue: Wolfson Lecture Theatre.
- Series: Bullard Laboratories Wednesday Seminars; organiser: Megan Holdt.
Wed 31 Jan 16:00: TBC
TBC
- Speaker: Max Van Wyk de Vries, University of Cambridge
- Wednesday 31 January 2024, 16:00-17:00
- Venue: Wolfson Lecture Theatre.
- Series: Bullard Laboratories Wednesday Seminars; organiser: Megan Holdt.