ESS Department - December 1st, 2022
Multiphase flows are ubiquitous in the world around us. Geophysical mass flows such as snow avalanches, mudslides, debris flows, and volcanic eruptions present significant natural hazards. Sediment transport processes in rivers, lakes, and oceans affect the health of freshwater, estuarine, and benthic ecosystems, while magma flows shape the evolution of Earth’s crust. A common feature shared by the above environmental multiphase flows is the enormous range of length scales to which they give rise, from droplets and clay particles of micrometer size to atmospheric weather systems and ocean currents exceeding thousands of kilometers. The resulting multiscale nature renders the exploration of environmental multiphase flows by laboratory experiments, numerical simulations, field o bservations and remote sensing highly challenging. I will review the latest developments and new directions that employ common organizing principles across the...
ESS Department - November 17th, 2022
Oxygen isotopes, measured in microstructural context using secondary ion mass spectrometry (SIMS), are emerging as a tool to dissect high-temperature fluid-rock interactions. Our group recently obtained some of the first in situ SIMS oxygen isotope data for metamorphic core complexes, demonstrating interactions between meteoric water and footwall mylonites. Inter-grain and intra-grain oxygen isotope variations help constrain the temperatures and the timings of meteoric fluid infiltration along the core complex-bounding detachment faults. These data inform understanding of evolving core complex rheology, as well as models of metamorphic core complex formation and thermal evolution.
ESS Department - November 10th, 2022
This study investigates the anisotropic structure of the Earth’s upper mantle, and focuses on what the mantle anisotropy tells us about the dynamics of the oceanic mantle and the formation of the continents. The mantle anisotropic model is built from an analysis of more than 5x10^6 seismic waveforms, and the model is developed by jointly inverting for isotropic shear wave speed (Vs) and radial anisotoropy (ξ) along each path. The path-average Vs and ξ measurements are tomographically inverted for a 3D Vs and ξ model. Beneath the ocean basins, the average ξ increases from ~1.03 below the Moho, peaks at ~1.06 at ~150 km depth, decreasing to ~1 at ~250 km depth. The thickness of the ξ>1 layer increases slightly with the increasing age of the oceanic lithosphere. At >200 km and deeper below the East Pacific Rise, and starting at somewhat greater depths beneath the slower spreading ridges, ξ<1. The Vs signature of the mid-ocean ridges...