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EPSS Colloquium - Winter-2018

Flavors of Pacific Northwest Earthquakes

Jan. 9, 2018
3:30 p.m. - 4:30 p.m.
geology 3656

Presented By:

  • John Vidale - USC
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Sudden mayhem. Tremendous impact. Unpredictable disruption. Is it any wonder earthquakes reserve a dark corner in our nightmares? The Pacific Northwest is vulnerable to several shades of shakes: giant coastal quakes, isolated, 50-km-deep pops, and crustal rips that could tear Seattle's (or Tacoma's, or Olympia's, or Portland's) downtown apart. The University of Washington's M9 Project, is making the repercussions of PNW quakes clearer and both less and more frightening.

Surface processes reveal hidden active faults in the Himalaya and Cascadia

Jan. 16, 2018
3:30 p.m. - 4:30 p.m.
geology 3656

Presented By:

  • Kristin Morell - UCSB
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In this presentation I will describe how coupling landscape processes to active tectonics can constrain the dynamics of crustal deformation in active mountain ranges. In particular, I will show examples of 1) how river profiles elucidate along-strike and across-strike variations in strain accumulation in the NW Himalaya; and 2) how lidar topography combined with paleoseismic trenching reveals previously unidentified active faults in the Canadian forearc of the Cascadia subduction zone.

Environmental sustainability at the intersection of climate and human change

Jan. 23, 2018
3:30 p.m. - 4:30 p.m.
geology 3656

Presented By:

  • Efi Foufoula-Georgiou - UCI
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Climatic trends and intensive exploration of landscapes are changing water cycle dynamics in unprecedented and often unfavorable ways. In this talk I will use as example a prototype intensively managed agricultural landscape in the Midwestern US where agricultural production is thriving but threatening the health of receiving waters from the local basin scale to the Gulf of Mexico hypoxic zone. The scientific challenges, and our approach in meeting them, will be presented including 1) the multiple processes that need to be modeled in minimally parameterized models (hydrology, sediment production and transport, river biota, nitrogen exports) 2) the wide range of temporal and spatial scales over which system understanding is needed 3) the need to identify process thresholds that can trigger unsustainable change 4) the need for a comprehensive and strategic program of field monitoring, laboratory testing, and multi-scale modeling to gain system understanding and 5) the challenge of putting science into practice to suggest effective management and policy options.

The Magnetic Sun

Jan. 30, 2018
3:30 p.m. - 4:30 p.m.
geology 3656

Presented By:

  • Vasyl Yurchyshyn - BBSO
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In this talk I will introduce the 1.6 meter Goode Solar Telescope (GST) and the novel instrumental work on adaptive optics that the BBSO team is doing in Big Bear. The presentation will also briefly review several studies performed by the NST team that are focused on fine-scale structures of quiet Sun, solar flares, and sunspots. The research areas that will be discussed include moving magnetic features, Ellerman bombs, formation of sunspot penumbra and waves, sunspot evolution, a white light flare, small-scale dynamics in the penumbra, as well as small scale phenomena such as magnetic field dissipation, chromospheric spicules, and jets.

Extensional Terrains: Tectonic windows into ocean worlds

Feb. 6, 2018
3:30 p.m. - 4:30 p.m.
geology 3656

Presented By:

  • Samuel Howell - JPL
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The tectonic and magmatic processes that link planetary interiors to their surfaces fundamentally affect surface morphology, environment, and potential habitability. Recent discoveries of present-day oceans beyond Earth have further motivated the study of surface-interior interactions, and analogue processes for terrestrial plate tectonics have been proposed on the icy moons of Jupiter. Because direct observations of interior mechanics are impossible, I will present research that explores the surface expression of numerically simulated tectonic and magmatic processes at Earths mid-ocean ridges and the icy bands of Europa and Ganymede.

Climate Reconstruction from Tree-Rings. AKA, how the past informs us about the future

Feb. 13, 2018
3:30 p.m. - 4:30 p.m.
geology3656

Presented By:

  • David Frank - UAZ
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The growth rings of trees are an archive of plant responses to environmental change, and as such they have played an important role in reconstructing climate over the past centuries to millennia at annual resolution. Nearly everyone is familiar with tree-rings themselves, and can intuitively understand many applications of dendrochronology. Yet the process to reconstruct climate variation, and the climate reconstructions themselves, have been subject to misconceptions, uncertainty, and controversy. Some of this is part of the scientific process, and some is not. In this talk I aim to set the stage for a discussion about “everything you always wanted to know about tree-rings, but were afraid to ask” by providing an introduction to dendroclimatology. I will share our current understanding of temperature and hydroclimatic variation over the past 1-2 millennia. And I will also show examples of how tree-ring reconstructions have been, and could have been, applied to improve policy decisions and the management of resources.

Global Geology of Titan from Cassini

Feb. 20, 2018
3:30 p.m. - 4:30 p.m.
Geology 3656

Presented By:

  • Rosaly Lopes - JPL
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Titan has shown itself to be one of the solar system's most intriguing objects for study, with a variety of unusual candidate materials on its surface, such as hydrocarbons. Titan is very geologically complex, and features found include large craters, cryovolcanoes, mountains, flowing channels, vast fields of dunes, and giant lakes and seas of liquid hydrocarbons. Titan is very Earth-like in its geology, despite the very different surface conditions and composition, and has become known as "the Earth of the outer solar system". This talk will discuss the global distribution and origin of different surface units.

Microbial biosignatures in sedimentary rocks

Feb. 27, 2018
3:30 p.m. - 4:30 p.m.
geology3656

Presented By:

  • Tanja Bosak - MIT
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How to recognize signs of life in past sediments from Earth or other planets? Signatures of microbial life are preserved from 80 percent of Earth's history, but these biosignatures can be difficult to recognize or interpret. Specifically, it is often unclear to what extent microbial metabolisms and microbial interactions with minerals and sediments promote fossilization in siliciclastic sediments. This talk will highlight some questions that arise from the record on the early Earth and address them by taphonomic experiments. The utility of these insights will be also discussed in the context of the search for life on early Mars.

Explosions in the Sky: Modeling Asteroid Airbursts

March 6, 2018
3:30 p.m. - 4:30 p.m.
geology 3656

Presented By:

  • Mark Boslough - Sandia Labs
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Computational models of asteroid airbursts on Earth are rooted in simulations of the 1994 impact of Comet Shoemaker-Levy 9 on Jupiter. The 1908 Tunguska explosion in Siberia is the best-known example. Models suggest that the altitude of maximum energy deposition is not a good estimate of the equivalent height of a point explosion. The 2013 Chelyabinsk event yielded direct observational data that could be compared to models, confirming this conclusion. The center of mass of an exploding projectile maintains a significant fraction of its initial momentum and is transported downward and forward. The fireball - a hot jet of ablated asteroid - descends to a depth well beneath the burst altitude before its velocity becomes subsonic. Stronger blast waves and thermal radiation pulses are therefore experienced at the surface than for an equivalent nuclear explosion. In the Tunguska case, the jet lost its momentum before making contact with the Earth's surface. For impacts above some energy threshold, the fireball reaches the ground, expands radially, and drives supersonic hot winds that can melt surface materials. The Libyan Desert Glass event (~29 million years ago) may be an example of this second, larger and more destructive type of airburst. Recent research has suggested that such airbursts can generate tsunami waves, but the efficiency of this coupling remains controversial. Better understanding of airbursts, combined with the diminishing number of undiscovered large asteroids, leads to the conclusion that airbursts represent a large and growing fraction of the total impact threat. The most effective policies to reduce the impact threat would therefore be to raise awareness of tsunami risk even in seismically inactive ocean basins, and to resurrect the old cold-war duck-and-cover concept to minimize casualties from air blast effects.

A case for the Millennium Eruption of Paektu volcano, North Korea

March 13, 2018
3:30 p.m. - 4:30 p.m.
geology 3656

Presented By:

  • Kayla Iacovino - ASU
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Magmatic volatiles such as H2O, CO2, sulfur, and halogens (e.g. F, Cl) are injected into the atmosphere during explosive volcanic eruptions and can drive globally significant climate change. Accurate quantification of volatile yield and composition is critical in assessing the impact of an eruption but is elusive, particularly for pre-historic or unmonitored eruptions. We utilize a geochemical technique to calculate C-O-H-S-F-Cl gas composition and mass yield from silica-rich explosive volcanoes by examining trends in incompatible trace and volatile element concentrations in crystal-hosted melt inclusions. We apply this technique to one of the largest volcanic eruptions in recorded human history, the 946 CE Millennium Eruption (ME) of Paektu (Changbaishan) volcano, which produced comenditic tephra and a caldera that straddles the border between the Democratic Peoples Republic of Korea (DPRK) and China. We calculate a sulfur yield of up to 45 Tg S from the ME. An estimated column height of 29 km indicates injection of much of this S into the stratosphere. This sulfur yield is 1.5 times that released during the eruption of Tambora in 1815, which resulted in significant global cooling in 1816. We suggest that the minimal climate perturbations after the Millennium Eruption as inferred from polar ice cores was due to the high latitude and season of the eruption and is not reflective of the significant S output. Our work places the Millennium Eruption among the top ranking volcanic volatile emitters in recorded human history.