Upcoming Events

Guide for Seminar Speakers
Seminar Chair: Krista Soderlund •••• Brown Bag Organizer: Sophie Goliber

	April 2018
Mon	Tue	Wed	Thu	Fri	Sat	Sun
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2	3	4 Brown Bag Seminar: Jiachao Liu Brown Bag Seminar: Jiachao Liu April 4, 2018 @ 12:00 pm - 1:00 pm Seminar Conference Room 10100 Burnet Road, Bldg 196-ROC Austin, TX 78758 United States Informal weekly presentations by UTIG students and researchers. Bring your lunch! See more details •	5	6 Seminar: Adrian Lenardic, Rice University Seminar: Adrian Lenardic, Rice University April 6, 2018 @ 10:30 am - 11:30 am Seminar Conference Room 10100 Burnet Road, Bldg 196-ROC Austin, TX 78758 United States Watch live. Title: The Asthenosphere, Mantle Convection, and the Dynamics of Plate Tectonics Abstract: Since the discovery of plate tectonics it has been suspected, but never fully demonstrated, that a low-viscosity layer beneath the plates (i.e., the asthenosphere) may play a central role in facilitating their motions.This idea has cast a significant shadow not only on Earth dynamics but also on comparative planetology - in particular on Earth-Venus comparisons. We review constraints on the structure and viscosity of the asthenosphere that are provided by geoid and post glacial rebound studies. We also review previous numerical simulations that highlighted the potentially key role that a rheologically weak asthenosphere, interacting with plates above, could play in maintaining plate tectonics on Earth. We then present new models that expand explorations into the defining characteristics of the asthenosphere and its role for the mantle convection and plate tectonics. The collective works leads us to suggest a geodynamic definition of the asthenosphere that breaks from the traditional view that the principal role of the asthenosphere, for plate tectonics, is to provide basal lubrication for plates. Learn more about Dr. Lenardic . Host: Thorsten Becker See more details •	7	8
9	10	11 Brown Bag Seminar: Rodrigo Lima Brown Bag Seminar: Rodrigo Lima April 11, 2018 @ 12:00 pm - 1:00 pm Seminar Conference Room 10100 Burnet Road, Bldg 196-ROC Austin, TX 78758 United States Informal weekly presentations by UTIG students and researchers. Bring your lunch! See more details •	12	13 Seminar: James Tuttle Keane, Caltech Seminar: James Tuttle Keane, Caltech April 13, 2018 @ 10:30 am - 11:30 am Seminar Conference Room 10100 Burnet Road, Bldg 196-ROC Austin, TX 78758 United States Watch live. Title: The Wibbly Wobbly Moon: The Rotational Dynamics of the Moon Over Time Abstract: The spins of planets and moons are not constant with time; they change in response to both external and internal forces on a variety of spatial and temporal scales. These changes can have important consequences for the geology of a planet, including stirring up the core dynamo, generating tectonic stresses in the crust, and altering the stability of water and other volatile ices across the planet's surface. Beyond the Earth, the Moon is the only other solar system body where we have been able to constrain multiple aspects of its rotational history. In this seminar, I will present a variety of new results detailing our investigations into the Moon's rotational dynamics over time: from long-term true polar wander due due to mantle convection, to chaotic tumbling due to giant impacts. While I will focus on the Moon, these dynamical processes are incredibly general, and I will touch on some prospects for future analogous studies of Mercury, Venus, Mars, and the icy worlds. Learn more about Dr. Keane. Host: Duncan Young See more details •	14	15
16	17	18 Brown Bag Seminar: Tyler Meng Brown Bag Seminar: Tyler Meng April 18, 2018 @ 12:00 pm - 1:00 pm Seminar Conference Room 10100 Burnet Road, Bldg 196-ROC Austin, TX 78758 United States Informal weekly presentations by UTIG students and researchers. Bring your lunch! See more details •	19	20 Seminar: Jean-Arthur Olive, l'Ecole Normale Supérieure Seminar: Jean-Arthur Olive, l'Ecole Normale Supérieure April 20, 2018 @ 10:30 am - 11:30 am Seminar Conference Room 10100 Burnet Road, Bldg 196-ROC Austin, TX 78758 United States Watch live. Title: Shaping slow-spreading seafloor with detachment faults Abstract: While seafloor formed at intermediate- and fast-spreading mid-ocean ridges shows little variability in the along-axis direction, the morphology of slow-spread seafloor is inherently three-dimensional. Within tens of km along a slow ridge segment, the landscape can change from regularly-spaced basaltic hills bounded by short-offset faults to dome-shaped exposures of mantle units capped by a large-offset detachment. Because most previous modeling efforts have been confined to 2-D cross-axis sections, the mechanics of the along-axis transition between these two distinct modes of seafloor spreading is largely unknown. In a broader sense, the link between the sub-seafloor geometry / extent of a detachment fault and its expression at the seafloor remains contentious. I will address these questions through a combination of bathymetric analysis, 3-D thermo-mechanical modeling, and simple mechanical modeling. In the first part of the presentation, I will show that the along-axis extent and overall shape of detachment fault footwalls directly reflect along-axis gradients in the amount of magma supplied to the ridge axis. In the second part of the talk, I will discuss the way seafloor-shaping processes (e.g., mass wasting) continuously rework detachment fault footwalls and complicate the tectonic interpretation of bathymetry. Together, these efforts greatly improve our ability to interpret seafloor morphology in terms of underlying geodynamic processes. Learn more about Dr. Olive: https://jaolive.weebly.com/ Host: Luc Lavier See more details •	21	22
23	24	25 Brown Bag Seminar: Stefano Nerozzi Brown Bag Seminar: Stefano Nerozzi April 25, 2018 @ 12:00 pm - 1:00 pm Seminar Conference Room 10100 Burnet Road, Bldg 196-ROC Austin, TX 78758 United States Informal weekly presentations by UTIG students and researchers. Bring your lunch! See more details •	26	27 Seminar: Vera Schulte-Pelkum, University of Colorado Boulder Seminar: Vera Schulte-Pelkum, University of Colorado Boulder April 27, 2018 @ 10:30 am - 11:30 am Seminar Conference Room 10100 Burnet Road, Bldg 196-ROC Austin, TX 78758 United States Watch live. Title: Deep crustal evolution, continental deformation, and the roots of faults from seismology and xenoliths Abstract: I will present two studies that combine seismic and xenolith data to investigate continental assembly, evolution of deep crustal structure, and deformation along faults and their ductile roots of the North American continent. The first study uses EarthScope and pre-existing active source seismic data and xenolith studies to map the distribution of high-velocity lower crust, indicating mafic or garnet-bearing material, across the U.S. and assess its relationship to proposed emplacement and loss mechanisms such as under- and intraplating, collision, extension, heating, cooling, hydration, and delamination. Thin layers of high-velocity crust related to regional processes are found scattered throughout the continent. Thicker layers in large areas are found in the central and eastern U.S. in areas with thick crust, bounded roughly by the Rocky Mountain Front, which cuts across Proterozoic assembly provinces. Hence, the modern north-south first-order contrast in structure may reflect garnet growth with aging of continental crust in much of the central and eastern U.S., while conditions in the western U.S. are unfavorable for growth and maintenance of thick layers of high-velocity garnet-bearing lower crust. We find areas with differences between the seismically defined Moho and the petrological crust-mantle boundary. The second project combines laboratory data from xenoliths and anisotropic receiver functions to map fault zones and shear zones in the lithosphere. We developed a method to image contrasts in azimuthal anisotropy, dipping rock fabric, and dipping isotropic contrasts based on azimuthally varying conversions in receiver functions. Unlike shear wave splitting, azimuthally varying P to S conversions provide a large-amplitude, robustly observable signal even for small (few percent) contrasts in anisotropy in thin (few km) shear zones and provide depth resolution. Strikes from receiver functions typically align with surface fault traces in tectonically active regions, with depths of the converters extending into the ductile regime. Interpretation of observed seismic anisotropy requires knowledge of underlying symmetry systems, which are not well determined for the crust. We analyze a compilation of whole rock elasticity tensors from ultrasound and microstructural laboratory measurements. Our collection contradicts the commonly made assumption of elliptical hexagonal anisotropy; we observe that crustal anisotropy deviates from the elliptical case with increasing strength of anisotropy, which changes inferred anisotropy amplitudes and orientations in receiver function and surface wave studies. Our observations suggest that reactivation of inherited structures may play a significant role in present day deformation. Learn more about Dr. Schulte-Pelkum: https://www.colorado.edu/geologicalsciences/vera-schulte-pelkum Host: Thorsten Becker See more details •	28	29
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