Társilo Girona, University of Alaska Fairbanks
Low-temperature thermal anomalies as a precursor to volcanic eruptions
February 4, 2022 at 3:00 pm (Zoom)
Identifying the observables that warn of volcanic unrest and eruptions is one of the greatest challenges in natural hazard management. An important observable is the release of heat through volcano surfaces, which represents a major energy source at quiescent volcanoes. However, many questions remain open: To what extent are volcanic eruptions preceded by an enhancement of low-temperature (~ambient) thermal anomalies at the surface? Is there a direct correlation between low-temperature thermal anomalies and the subsurface processes preceding volcanic eruptions? In this talk, I will address these questions by using different volcanoes as case studies, including Nyiragongo (Congo) and Cumbre Vieja (La Palma, Spain), two of the most socially impactful volcanoes in 2021; and numerical simulations. More information on this work can be found in these papers: https://www.nature.com/ articles/s41561-021-00705-4, https://www.nature.com/ articles/s41598-020-67982-8, and https://www.pnas.org/content/ 118/2/e2020943118.
Diana Roman, Carnegie Earth and Planets Laboratory
Multi-Disciplinary Evidence for a Large, Previously Unrecognized Caldera in the Islands of Four Mountains, Aleutian Arc, Alaska
February 11, 2022 at 3:00 pm (PLS 1140)
Large caldera-forming eruptions (CFEs, VEI ≥ 6) are one of the greatest and most globally transformative natural hazards. Knowledge of their location, history, and the magmatic processes that drive caldera formation is critical for understanding Earth’s past climate and preparing for hazards associated with future eruptive activity. The eastern Islands of Four Mountains (IFM) are a volcanic archipelago in the central Aleutian arc comprised of six closely spaced stratovolcanoes (Cleveland, Carlisle, Uliaga, Kagamil, Tana and Herbert) and a number of subsidiary cones and fissures. The remote location, difficulty with access, and perpetually poor weather have long precluded in-depth investigations of Aleutian volcanoes, yet they pose hazards to overflying aircraft, boat traffic, and local communities. Here we present multi-disciplinary evidence that includes bathymetry, gravity, geologic deposits, earthquake hypocenters, gas chemistry and locations of fumaroles, and structural trends and volcanic vent morphology, that suggest that volcanism in the IFM may be influenced by a large, previously unrecognized caldera that is largely hidden by the ocean and recent geologic deposits. The existence of a large caldera in the IFM would help explain the persistent activity at Mount Cleveland, the most active volcano in North America since at least 2001.
Julie Rathbun, Planetary Science Institute
Part 1: “Burdened with Glorious Purpose: Understanding Loki and Io’s other active volcanoes”
Part 2: “Who is missing in planetary science?"
February 18, 2022 at 3:00 pm (Zoom)
Rhonda Stroud, US Naval Research Laboratory
Fresh Dirt from the Dawn of the Solar System: A First Look at Hayabusa2 Returned Samples from Asteroid Ryugu
March 18, 2022 at 3:00 pm (PLS 1140)
The Japanese Space Agency (JAXA) sent the Hayabusa2 spacecraft to asteroid Ryugu to collect and return samples of a carbonaceous (C-type) asteroid. Although carbonaceous chondrite meteorites have been assumed to originate in C-type asteroids, the Hayabusa2 mission samples are the first available for laboratory study that have a definitive link to specific asteroid. The Hayabusa2 sample return capsule arrived back on Earth on December 6, 2020, with Ryugu particle samples totaling more than 5 grams from two distinct sampling sites. Initial Analysis of the samples is underway by teams of researchers world-wide. The first results of laboratory studies confirmed some expectations, e.g., Ryugu has abundant organic carbon, but also provided some surprises, e.g., Ryugu shows extensive hydration and is less heated than expected from remote sensing observations. Overall, the Hayabusa2 samples have much in common with CI meteorites, particularly Orgueil. However, their known astronomical origin and pristine state with limited exposure to terrestrial contaminants makes them among our most valuable samples for searching for signatures of the chemistry of the early solar system.
Natalie Burls, George Mason University
How will the tropical Pacific respond to global warming? The importance of timescale when considering apparent paleo-paradoxes
April 1, 2022 at 3:00 pm (PLS 1140)
Several oceanic and atmospheric mechanisms have been put forward to describe the response of the tropical Pacific to global warming. Still uncertainties persist in their interaction and relative importance, with projections varying substantially across climate models. When we turn to the last time in Earth’s history that atmospheric CO2 estimates exceed 400 ppm, the Pliocene, several apparent paradoxes related to the equatorial east-west sea surface temperature (SST) gradient appear. These paradoxes cloud our view of the tropical Pacific during the Pliocene and its utility as a potential analogue for future warming. However, as I will cover in this talk, when proper consideration is given to the timescales associated with the oceanic and atmospheric mechanisms that support tropical Pacific climate variability, several of these apparent paradoxes can be resolved.
Marc Hirschmann, University of Minnesota
Silicate melting on planets and planetesimals and the path towards Earth-like planets
April 15, 2022 at 3:00 pm (PLS 1140)
Two properties of Earth that influence its character and possibly its habitability are the depletion in volatiles compared to cosmochemically available sources and the relatively oxidized character of its interior. The former is of significant influence to the operation of deep planetary volatile cycles and the large-scale controls on atmospheric and climatic evolution. The latter is of importance to both the internal dynamics of the planet as well as to the path towards an oxidized surface environment.
In this talk, I will consider two ways in which silicate melting played an important role in these. First, considering volatile loss, I will examine evidence from iron meteorites which suggests that early planetesimals experienced significant volatile loss owing to silicate melting. To the extent that earth-like planets are formed from planetesimals, it is this early melting that may be a crucial portion of their volatile-depletion. Second, I will discuss how high pressure equilibration between silicate melts and core-destined iron-rich alloy plays an important role in establishing the early oxidized state of earth-sized planets. However, the evolution of interior oxidation of terrestrial oxidation is complex, and I will also discuss several additional processes in need of further consideration.
Don Fisher, Penn State
Interseismic Deformation, Fluid flow, and Great Subduction Zone Earthquakes: Insights from the Rock Record
April 22, 2022 at 3:00 pm (PLS 1140)
Subduction interfaces are loci of interdependent seismic slip behavior, fluid flow, and mineral redistribution. Mineral redistribution leads to coupling between fluid flow and slip behavior through decreases in porosity/permeability and increases in cohesion during the interseismic period. We investigate this system from the perspective of ancient accretionary complexes with regional zones of mélange that record noncoaxial strain during underthrusting adjacent to the subduction interface. Deformation of weak mudstones is accompanied by low-grade metamorphic reactions, dissolution along scaly microfaults, and the removal of fluid-mobile chemical components, whereas stronger sandstone blocks preserve veins that contain chemical components depleted in mudstones. These observations support local diffusive mass transport from scaly fabrics to veins during interseismic viscous coupling. Underthrusting sediments record a crack porosity that fluctuates due to the interplay of cracking and precipitation. Permanent interseismic deformation involves pressure solution slip, strain hardening, and the development of new shears in undeformed material. In contrast, coseismic slip may be accommodated within observed narrow zones of cataclastic deformation at the top of many mélange terranes. A kinetic model implies interseismic changes in physical properties in less than hundreds of years, and a numerical model that couples an earthquake simulator with a fluid flow system depicts a subduction zone interface governed by feedbacks between fluid production, permeability, hydrofracturing, and aging via mineral precipitation. During an earthquake, interseismic permeability reduction is followed by coseismic rupture of low permeability seals and fluid pressure drop in the seismogenic zone. Updip of the seismogenic zone, there is a post-seismic wave of higher fluid pressure that propagates trenchward.
Anne Pommier, Carnegie Earth and Planets Laboratory
Experimental Investigation of Planetary Interiors using Electrical Measurements
April 29, 2022 at 3:00 pm (PLS 1140)
Electrical measurements are one of few methods for exploring the physical and chemical state of planetary interiors. The interpretation of electrical data from field measurements and space observations requires laboratory experiments on natural or
analogous geomaterials performed at relevant temperatures and pressures. This presentation focuses on how electrical conductivity experiments at extreme pressures and temperatures are used to probe the structure and dynamics of the Earth and other terrestrial bodies. In particular, two examples, applied to cratonic contexts and to metallic cores, will be highlighted.
The coordinator for the Colloquium Series is Dr. Megan Newcombe. You can contact her at firstname.lastname@example.org.