Date/Time
Date(s) - Thu 25 June
19:00 - 20:00
Location
Lecture Theatre One (GBLT1), Old Government Buildings, VUW
GSNZ Wellington branch meeting
The Transantarctic Mountains – the curious case of a mountain range that popped up twice out of nowhere, with Tim Stern, Professor-Emeritus of Geophysics, Victoria University of Wellington
The Transantarctic Mountains (TAM) form a long (~ 3000 km) and high (~4600 m) range between East and West Antarctica, which have risen in two distinct episodes starting at about 105 and 55 Ma. These mountains have long been a geological enigma because, unlike other major mountain ranges, they have formed well away from zones of plate convergence.
Professor-Emeritus Stern proposes that the origin of the TAM lies not just in what has happened in the crust, but also much deeper down at the bottom of the tectonic plate. The central idea is that the lithospheric mantle is potentially unstable because It is colder, and hence more dense, than the underlying asthenospheric mantle. Given the right conditions, this part of the lithosphere – possibly together with the mafic lower crust – can detach itself from the overlying crust and sink into the asthenosphere, thereby removing a massive ‘anchor’ which allows the overlying crust to bob up. In detail, the detachment forms a commonly observed phenomenon in fluid dynamics called a Rayleigh-Taylor instability.
This process provides a context to explain two recent discoveries: firstly, Miocene volcanics in the southern TAM, about 300 km inland from the edge of the ranges and just 200 km from South Pole (2018); and secondly, the very recent (Science, May 26, 2026) discovery of mantle earthquakes located deep beneath the TAM.
Professor-Emeritus Stern shows that the 50 my gap between the two erosion/uplift events is a natural outcome of an evolving mantle instability, and is common to many rift or passive margins. If so, Rayleigh-Taylor instabilities of the continental mantle are likely to be a global phenomenon and one of the key mechanisms for the stabilisation and preservation of continental crust. The TAM are one of the critical localities in the world to study this process.
This talk will be available live via Zoom but not recorded.
Contact: wellington@gsnz.org.nz