UTIG Brown Bag: Andrew Gase, UTIG

Informal weekly presentations by UTIG students and researchers. Bring your lunch!

Speaker: Andrew Gase, Graduate Research Assistant, UTIG

DeFord Lecture: Christie Rowe

UTIG Seminar Series: William Moore, Hampton University

Click to watch online.

Speaker: William Moore, Hampton University

Host: Thorsten Becker

Title: Venus: How Heat Pipes Closed the Window on Plate Tectonics

Abstract: Venus, like the smaller terrestrial bodies but unlike Earth, exhibits single-plate, rigid lid tectonics and a surface dominated by voluminous plains-forming volcanism. The absence of plate tectonics on Venus has long been a puzzle, since buoyancy forces should be quite similar to Earth. One major difference between the two planets is the surface temperature, which is 430 degrees C hotter on Venus. Venus’ surface is nearly twice as close to the melting point of rocks as Earth’s. For any terrestrial planet, the difference between the surface temperature and the solidus determines the maximum amount of heat that can be transported without melting the mantle. If the heat production exceeds this level, melt will be produced and erupt at the surface, carrying the excess heat in what is known as the heat-pipe mode of planetary heat transfer. This means that a planet with a higher surface temperature, will sustain significant volcanism at lower heat production rates, since sub-solidus convection is less efficient. As planets cool from a hot state and gradually lose heat producing elements, a planet with an elevated surface temperature takes longer to exit the heat-pipe mode from a given initial heat production rate, and this exit takes place at a lower heat production rate. Since heat-pipe volcanism suppresses lithospheric stresses (through the capping of temperatures and flattening of isotherms by the solidus), any opportunity to initiate plate tectonics therefore takes place later and at lower heat production rates and lower lithospheric stress on a planet with a higher surface temperature. If those stresses are insufficient to break the lithosphere, rigid-lid evolution results. This hypothesis explains a number of features of Venusian geology that previously have been explained by strongly non-monotonic behavior which is difficult to reconcile with evolution from a hot initial state. Instead, the extensive plains volcanism, the apparently thick lithosphere, the uniform crater distribution, and the relatively old age of elevated crust are all explained by the rapid cessation of heat pipe volcanism approximately 1 billion years ago, a delay of about 2 billion years (roughly one half life of mantle heat sources) relative to Earth. Venus’ extended childhood has therefore caused it to miss its window of opportunity to undergo plate tectonics and it is now stably trapped in the rigid lid state.

Barb Cohen, NASA Goddard

Talk on In situ geochronology on Mars and the development of future instrumentation

Steve Forman, Baylor University

Talk on: Luminescence dating to quantify eolian depositional process on Earth and Mars on decadal to million year-timescales

UTIG Brown Bag: Stefano Nerozzi, UTIG (PhD Talk)

Informal weekly presentations by UTIG students and researchers. Bring your lunch!

This week: Stefano Nerozzi presents his PhD defense talk!
"Reconstructing the early emplacement of the north polar cap of Mars"

Speaker: Stefano Nerozzi, Graduate Research Assistant, UTIG

De Ford Lecture Series: John Doherty

Doug Ming, NASA Johnson Space Center

Talk on: Sedimentary Deposits on Mars from the Eyes of Rovers and Landers

DeFord Lecture: Gabriel Bowen

UTIG Seminar Series: Amy Clement, University of Miami

Click to watch online.

Speaker: Amy Clement, University of Miami

Host: Yuko Okumura

Hot Science - Cool Talk "Save the...Sharks!?"

“We have been hating sharks on general principles for centuries … now it is high time that they should pay up.” This was a 1928 invitation to harvest sharks in Scientific Monthly (now Science). This mentality has been accepted by generations of fishermen and fishery managers. However, modern science shows many of the world’s shark stocks have decreased to unprecedented levels, placing ocean ecosystems in peril. Through his research and interactions with sharks, Dr. Stunz will share the history and current status of their declines, and their future along the northern Gulf of Mexico.

DeFord Lecture: Brian Arbic

UTIG Brown Bag: Doug Foster, UTIG

Informal weekly presentations by UTIG students and researchers. Bring your lunch!

Speaker: Doug Foster, Senior Research Scientist, UTIG

DeFord Lecture: Marcello Coradini

UTIG Seminar Series: Anne Becel, Lamont-Doherty Earth Observatory

Click to watch online.

Speaker: Anne Becel, Lamont-Doherty Earth Observatory

Host: Shuoshuo Han

Title: Connections between along-strike variations in seismic structure and earthquake behavior at the Alaska Peninsula subduction zone

Abstract: Subduction zones worldwide exhibit striking variations in seismic activity and slip behavior along strike and down dip, and many factors have been invoked to explain this variability. The subduction zone off the Alaska Peninsula is characterized by marked changes in seismic behavior, earthquake rupture history and geodetic coupling over relatively small along-strike distances, making it an ideal location to examine controls on seismo- and tsunami-genesis.

Marine seismic reflection and refraction data acquired across this subduction zone with the R/V Marcus Langseth reveal substantial along-strike variations in structure and properties of the incoming oceanic lithosphere as well as differences in thickness and pore-fluid pressure within the subducting sediment layer. We propose the amount of water and sediment delivered into the subduction zone on the incoming plate are influencing seismic behavior throughout this system. Seismic data also reveal major downdip changes in seismic reflection character of the megathrust interpreted as a broadening of the deformation zone at depth and thought to represent a gradual transition from conditionally stable and stable-sliding regions. Last, seismic data show a structural architecture favorable to the generation of tsunami in one of the subduction zone segments that needs to be taken into account when considering hazards for this region.

De Ford Lecture Series: Paul Myrow

UTIG Brown Bag: Mark Cloos, UT

Informal weekly presentations by UTIG students and researchers. Bring your lunch!

Speaker: Mark Cloos, Professor, Department of Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin

DeFord Lecture: Freya George

UTIG Seminar Series: Jamin Greenbaum, UTIG

Click to watch online.

Speaker: Jamin Greenbaum, UTIG

Host: Don Blankenship

Title: Vulnerabilities to ice sheet retreat along East Antarctica’s Indo-Pacific margin

Abstract: Global average sea level was 6.6 to 9.4 meters higher than it is now during the last interglacial period, to which Antarctica must have contributed between 3.6 and 6.4 meters given the estimated contributions from other sources. Much attention has been given to the West Antarctic Ice Sheet (WAIS) due to the rapidly retreating Thwaites and Pine Island Glaciers; however, their combined maximum sea level contribution is limited to 83 cm and the maximum possible contribution of the WAIS, assuming a complete collapse, is limited to 3.3 meters. This sea level budgeting exercise, combined with satellite observations of coastal glacier thinning on the margin of the East Antarctic Ice Sheet (EAIS), motivated UTIG’s polar geophysics group to organize the International Collaborative Exploration of the Cryosphere through Airborne Profiling (ICECAP) consortium, resulting in what has become a decade-long campaign of interdisciplinary surveys that have now filled in every major data gap in the EAIS. Here I will highlight how our recent efforts in Princess Elizabeth Land (PEL) have revealed lithosphere that thinned due to Cretaceous breakup of Gondwana, resulting in a large area of the ice sheet grounded below sea level and vulnerable to climate-paced marine ice sheet instability. We show that the area of thinned lithosphere along coastal PEL is similar in extent to thin lithosphere in the conjugate area of India’s Bengal Basin –a region currently vulnerable to seawater inundation. I will conclude with an overview of ongoing efforts to characterize ice shelves and the seafloor along the Indo-Pacific margin, now the least understood area of Antarctica due to the presence of sea ice that complicates access by marine platforms.

UTIG Brown Bag: Cornelia Rasmussen, UTIG

Informal weekly presentations by UTIG students and researchers. Bring your lunch!

Speaker: Cornelia Rasmussen, Postdoctoral Fellow, UTIG