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Fall 2017 Colloquia

Thursday, September 21st, 2017

John McCloy, Washington State University School of Mechanical and Materials Engineering
Title: Understanding the History of 1500-Year-Old Glass at Pre-Viking Swedish Vitrified Hillfort Site
Host: Julie Bowles

Abstract:
Geosciences have from the beginning been an integral part in robust planning and execution of nuclear waste management – from mineralogy of stable host phases for radioactive elements, to geochemistry of transport in the subsurface, to seismic and long term geophysical modeling of candidate repository sties for high level waste. This talk addresses yet another application, understanding and predicting the long-term degradation and alteration of emplaced glass using tools from various geoscience disciplines.

Nuclear waste must be immobilized and stored such that it does not cause significant impact on the environment or human health. In some cases, the integrity of the repositories will need to sustain for tens to hundreds of thousands of years. In order to ensure such containment, nuclear waste is frequently converted into a very durable glass. It is fundamentally difficult, however, to assure the validity of such containment based on short-term tests alone. To date, some anthropogenic and natural volcanic glasses, with ages of decades to thousands of years old, have been investigated for this purpose.

However, glasses produced by ancient cultures for the purpose of joining rocks in stonewalls have not yet been investigated as analogues, in spite of the fact that they might offer significant insight into the long-term durability of glasses in natural environments. Therefore, a project has been initiated with the scope of obtaining samples and characterizing their environment, as well as to investigate them using a suite of advanced materials characterization techniques. The objectives include determination of how the hillfort glasses may have been prepared, and to what extent they have altered under in-situ conditions. The ultimate goal is to obtain a better understanding of the alteration behavior of nuclear waste glasses and its compositional dependence, and thus to improve and validate predictive models for nuclear waste glass corrosion.

Broborg is an Iron Age site in Sweden dating ~450 AD. Evidence from field and experimental archaeology suggests that peoples were utilizing pyrotechnology to consolidate battlement walls. Sections of this “vitrified hillfort” still stand, indicating the durability resulting from this process. Excavations at Broborg and comparison with vitrified forts in other parts of Europe have suggested that at Broborg there was a practice of deliberate construction, based on melting amphibolite rock to consolidate gneissic-granite local boulders. Laboratory experiments have lent insight into requirements of local rock chemistry for melting using Iron Age pyrotechnology. Additionally, new excavations are planned for 2017 where paleomagnetic samples will also be collected, to confirm dating of the construction events based on recording of the earth’s magnetic field at the time of the crystallization of minerals like magnetite from the melted rock.

Given the presence of vitrified material of 1500+ years old, Broborg and similar sites provide a unique opportunity for studying long-term chemical durability of glass on a timescale relevant for application to models of nuclear waste glass alteration in geologic repositories.

Thursday, September 28th, 2017

Miles Traer, Stanford University (Video Presentation)
Title: Geology and Game of Thrones, Part 1
Host: UMW Department of Geosciences

Abstract:
Special guest Miles Traer discussed his “A Geologic Map of Game of Thrones” and talk about how pop culture can be an effective vehicle to communicate your science.

Miles Traer is a geological data scientist at Stanford University. He uses the tools of machine learning, Bayesian statistics, and physics-based models to investigate the creation and transformation of planetary surfaces. In his spare time, you can find Miles managing the award-winning Generation Anthropocene podcast, reconstructing the geological history of Game of Thrones, and calculating the carbon footprint of superheroes.

You can learn more about Miles and his science communication projects at milestraer.com and follow him on Twitter @Geo_Miles.

Tuesday, October 3rd, 2017

Kathy Sullivan – 7pm UNION BALLROOM — DEAN’S DISTINGUISHED LECTURE IN NATURAL SCIENCES
Title: Looking at Earth
Host: UW-Milwaukee

Abstract:
(taken from uwm.edu) 

Dr. Sullivan was the Under Secretary of Commerce for Oceans and Atmosphere and administrator of the National Oceanic and Atmospheric Administration (NOAA) from 2014 to 2017, a former astronaut, and the first American female to walk in space.

In addition to her NOAA and NASA roles, she was also President and CEO of the Center of Science & Industry in Columbus, Ohio; inaugural Director of the Battelle Center for Mathematics and Science Education Policy in the John Glenn School of Public Affairs at The Ohio State University; and Chief Scientist at NOAA where she oversaw research and technology for projects ranging from climate change to satellites and marine biodiversity.

Before and after the presentation, Boswell Book Company will be selling copies of Kathy’s children’s book, “To the Stars!: The First American Woman to Walk in Space,” which she co-authored with Carmella Van Vleet. Information about obtaining a signed copy will be forthcoming.

It’s UWM Homecoming Week – so we especially encourage alumni to come back and visit campus for this event.

A special thank you to Dr. Robert Greenler who helps underwrite this Dean’s Distinguished Lecture in the Natural Sciences.

Thursday, October 12th, 2017

Preston Jacobs, Rereading Fire, Rethinking Ice (Video Presentation)
Title: Geology and Game of Thrones, Part 2
Host: UMW Department of Geosciences

Abstract:
Special guest Preston Jacobs of Rereading Ice, Rethinking Fire will explore how geology has impacted events in the Game of Thrones series and how it may continue to affect the plot.

Thursday, October 19th, 2017

GSA practice talks/posters
Title: Various
Host: UMW Department of Geosciences

Thursday, November 9th, 2017

Laurel Goodwin, UW-Madison
Title: A Record of Earthquakes and Fault Mechanics Written in Stone
Host: Dyanna Czeck

Abstract:

An exhumed fault zone can preserve a record of earthquakes that extends over hundreds of thousands to millions of years. Recent studies indicate that such archives of earthquake information can be accessed effectively through integrated structural and isotopic analyses of appropriate fault rocks. In this talk, I will describe and explore the implications of two such records for better understanding the mechanics of extensional fault systems. U-Th dating of thirteen coseismic calcite veins in the Loma Blanca high-angle normal fault of the Rio Grande rift, NM, demonstrates remarkably periodic earthquakes with a recurrence interval of ca. 40ka over more than 400,000 years, consistent with recurrence intervals determined for shorter time intervals throughout the Basin and Range province. Interestingly, it also records a brief period in which the recurrence interval declines to 5-11 ka. Stable isotope analyses of the latter veins record fluid influx from a new source that fundamentally changed the seismic cycle. In contrast, 40Ar/39Ar dates on four low-angle normal, pseudotachylyte generation veins from the South Mountains metamorphic core complex, AZ, record a mean recurrence interval of 557 ka. The latter dataset, though much more limited in size, suggests that earthquakes produced by low-angle normal faults are far less likely to be sampled by the comparatively short-term instrumental and paleoseismic records.

High- and low-angle normal faults are commonly linked in networks, with numerous high-angle faults floored in a single low-angle detachment. I consider the implications of recurrence intervals that differ by an order of magnitude in light of this geometry. One possibility is that seismic slip at 40 ka intervals on multiple high-angle faults, which are optimally oriented for failure in extensional tectonic regimes, progressively loads low-angle normal faults, which are not, resulting in much longer recurrence intervals for earthquakes on the shallowly dipping structures. A second possibility is that this particular distribution of normal faults and slip rates minimizes the energy required to accommodate extension. These options are not mutually exclusive.

Thursday, November 16th, 2017

Christoph Geiss, Professor of Physics and Environmental Science, Trinity College
Title: Estimating the Likelihood of Concrete Failure Through Rock-magnetic Measurements
Host: Julie Bowles

Abstract:
Over the past decades pyrrhotite-containing aggregate has been used in concrete to build basements and foundations in central Connecticut. The sulphur in the pyrrhotite (Fe1-xS) reacts to several secondary minerals, and associated changes in volume lead to a loss of structural integrity. As a result hundreds of homes have been rendered worthless as remediation costs often exceed the value of the homes and the value of many other homes constructed during the same time period is in question as concrete provenance and potential future structural issues are unknown.
While minor abundances of pyrrhotite are difficult to detect or quantify by traditional means, the mineral is easily identified through its magnetic properties. All concrete samples from affected homes show a clear increase in magnetic susceptibility above 220°C due to the γ – transition of Fe9S10 [1] and a clearly defined Curie-temperature near 320°C for Fe7S8. X-ray analyses confirm the presence of pyrrhotite and ettringite in these samples. Synthetic mixtures of commercially available concrete and pyrrhotite show that the method is semiquantitative but needs to be calibrated for specific pyrrhotite mineralogies.

Thursday, November 30th, 2017

Esther Stewart, Wisconsin Geological and Natural History Survey
Title: Discovering hidden folds and faults in the Precambrian: Refining Baraboo interval stratigraphy and deformation in southernWisconsin
Description/Abstract
Host: Julie Bowles

Abstract:
The Paleoproterozoic Baraboo Quartzite (1710-1650 Ma) is present in the Baraboo Hills, Wisconsin, USA. It is one of several isolated quartzites outcropping across the southern Lake Superior region known as the Baraboo interval quartzites. These quartzites record a history of basin development followed by regional deformation along the south-central Laurentian margin. Baraboo interval stratigraphy in south central Wisconsin is unresolved, limiting understanding of the style and history of basin formation, sedimentation, and deformation, as well as correlation between regional quartzites.

New Precambrian geologic mapping focused on the core of the Baraboo syncline, Sauk County combined with regional subsurface Precambrian geologic mapping of Columbia, and Dodge Counties, WI refines the stratigraphy and large-scale deformation of the Baraboo interval in south-central Wisconsin. Mapping integrates traditional surface mapping, aeromagnetic and gravity anomaly data, drill core, historic drill records, drill cuttings, and well construction reports. Consistent with early interpretations of Baraboo interval stratigraphy, mapping suggests the Baraboo interval comprises two upward-fining sequences separated by an angular unconformity. The lower sequence comprises the Baraboo Quartzite, Seeley Slate, and Freedom Formation. The upper sequence comprises the Dake – Waterloo Quartzite and Rowley Creek Slate. The depositional age of the upper sequence is poorly constrained, though the Dake Quartzite must have been deposited after initiation of folding began in the Baraboo Hills area.