[Eoas-seminar] Geophysics Job Talk Today at 3:30 PM

[eoas-seminar at lists.fsu.edu]

Please attend

Geophysics Job talk by Johnny Seales @ 3:30 PM
Zoom link for the talk: https://fsu.zoom.us/j/99846006873

Title: Deep Volatile Cycles and the Thermal History of the Earth
Abstract: Volatile cycles play a key role in sustaining habitable surface conditions for the Earth. The cycling of volatiles between surface and interior reservoirs depends on the Earth’s internal dynamics. Volcanism transfers volatiles from the Earth’s interior to its surface, while subduction cycles volatiles into the interior. Here I will demonstrate the influence of the deep water and carbon cycles on the Earth system. The balance of water in the mantle affects mantle viscosity, which, in turn, influences convection and plate tectonics. Age dated rock samples suggest that Earth had a multi-staged cooling history. I will show that the first stage of less efficient mantle cooling is attributable to the effects of water cycling on mantle viscosity. A change from net mantle dewatering to rewatering is predicted to occur at approximately 2.5 billion years ago. This alters the relative influence of thermal to water cycling and leads to more rapid cooling. This timing coincides with the Great Oxidation Event which can also be connected to the coupling between volatile cycling and mantle dynamics. I will show that an increase in the flux of carbonates and organics, to different mantle depths, and delivery back to the surface can explain the rise of oxygen and the most positive d13C carbonate excursion in the Earth’s history. A final aspect I will explore is the role of deep volatile cycling on maintaining surface temperatures that allow for liquid water. We know that our own planet has had water at the surface for billions of years. Accounting for carbon and water cycling, I will show that terrestrial planets, akin to Earth, may have first had surface temperatures warm enough for liquid water over a time window that spans billions of years. This last analysis will show that Earth may fall in the tail of a galactic distribution of planets that allow for surface water over their evolutions.



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