Séminaire - Onset of plate tectonics on Earth and implications for habitability - Camille François (Site Buffon)

Lundi 7 janvier 2019, à 10 h 30

IMPMC, Salle des élèves, 2^e étage, 61 rue Buffon, Paris 5^e (entrer par le 43 rue Buffon, plan Vigipirates oblige)

Camille François - Université de Liège

Abstract
Understanding the geodynamic processes of the Early Earth is crucial because they have strong implications for the habitability of the Earth but also for other planets. The Earth is the only proven planet in the solar system with a plate tectonics. This phenomenon has played an important role in the evolution of our planet but may also have a significant impact on its sustained habitability. However, plate tectonics on Earth did not always function as today. Characterizing the transition from ancient to modern-style geodynamics regime, including plate tectonics and subduction process, is therefore important to understand the evolution of our own planet but also to compare our model to other rocky planets in our solar system and test their habitability.
Here, we characterize the oldest eclogite worldwide (2.1 Ga). These rocks are generally only produced in the geodynamic setting of subduction.  This discovery evidences a modern-style plate tectonics operating since at least 2.1 Ga. It highlights the fundamental differences between the ancient Earth, without plate tectonics, and the modern Earth, as we know it today. The appearance of plate tectonics had important impacts on Life evolution on our planet, with an increased supply of nutrients, increased diversity of ecological niches and geographic isolation leading to increased biodiversity, variable climatic conditions and oceanic circulation, as well as volcanic gases of different composition that may have influenced the composition of our atmosphere.