UMD: Boise State’s Kohn on Shear heating in subduction zones

2017 University of Maryland Geology Colloquium Series

Friday, November 17th 2017 at 3:00 pm
in PLS 1130, College Park campus

Matthew Kohn
Boise State University

Shear heating controls mineralogy, seismicity, and convection in subduction zones

Popular thermal-mechanical models of modern subduction systems are c. 300 °C colder at c. 50 km depth – the seismic-aseismic transition – than pressure-temperature conditions determined from exhumed metamorphic rocks, i.e. “Rocks are hotter than models” (Penniston-Dorland et al., 2015, EPSL). Subduction zone thermal structure is crucial for predicting depths of seismicity, fluid release, and sub-arc melting conditions. In this talk I will show that adding realistic shear stresses to thermal models quantitatively reproduces surface heat flow and the pressure-temperature conditions recorded by exhumed metamorphic rocks. A consistent seismic-aseismic transition depth of c. 50 km, however, is difficult to explain through mineralogical or thermal weakening mechanisms. Rather, I propose that mechanical removal of rheologically weak and buoyant rocks along the subduction interface leads to seismic decoupling and dynamic coupling bet! ween slab and mantle to drive mantle wedge convection and arc volcanism.


GSW 1524: Bentley on geological visualization

The 1524th meeting of the Geological Society of Washington will be on
Wednesday, December 6, 2017
featuring :

Presidential address

Visualization in Geology:
a brief history, best practices, & dispatches from the future

Stretched belemnite from the Alps
Callan Bentley, Northern Virginia Community College

(GSW’s 124th Annual Meeting to follow.)

Refreshments at 7:30 PM; Formal program at 8:00 PM
John Wesley Powell Auditorium, 2170 Florida Avenue NW, Washington, DC
(see here for directions)

AEG: Ground Vibration Control from Explosives Demolition of the Kosciuszko Bridge

Association of Environmental & Engineering Geologists

D.C. – Maryland – Virginia Chapter (

Thursday, November 16, 2017, from 5:30 PM to 7:45 PM
at Brewer’s Alley in Frederick, MD

AEG Members $40, Non-members $45 (includes dinner; student and retiree discounts available). Please RSVP by Monday, November 13, via email ( or via online payment (

Patrick T. Hastings, G.I.T. and David K. Miller, P.G.

Seismic Surveys, Inc.

Ground Vibration Control from Explosives Demolition of the Kosciuszko Bridge

The project involved designing and building the new eastbound structures of Interstate 278 over the Newtown Creek from Brooklyn to Queens, New York City, and the subsequent explosives felling of the existing Kosciuszko Bridge. The explosive demolition of the old Kosciuszko Bridge included 10 steel trusses on the Brooklyn approach and 10 steel trusses on the Queens approach. This presentation discusses the methods and procedures that were developed to protect third-party buildings, buried gas transmission pipelines, the Long Island Railroad, the Historical Old Calvary Cemetery and the new K-Bridges. During the explosive demolition on October 1, 2017, SSI used 52 seismographs at adjacent structures to monitor vibrations. The conclusion of the presentation will include a video compilation of Controlled Demolition, Inc. (CDI) successful explosives felling of the 3,104’ long, 20-span, structural steel, iconic Kosciuszko Bridge.

Please refer to our meeting announcement for full details (

UMD: Le Mével on volcanic unrest at large silicic systems

2017 University of Maryland Geology Colloquium Series

Friday, November 10th 2017 at 3:00 pm
in PLS 1130, UMD- College Park

Hélène Le Mével
DTM/Carnegie Institution for Science

Geodetic measurements and numerical models of volcanic unrest at large silicic systems.

I will examine the ground deformation associated to non-eruptive unrests at two volcanic systems: the Laguna del Maule volcanic field (Chile), experiencing high uplift rates since 2007, and the Long Valley caldera (USA), experiencing multiple episodes of surface uplift over the last 40 years. I will present results from analytical and numerical models to interpret these episodes of ground deformation in terms of magmatic processes.

Paleontological Society of Washington November seminar

The Paleontological Society of Washington

7:00 pm, Wednesday, November 15

National Museum of Natural History, Constitution Ave. entrance

An Amateur’s Collection of Corals from the North East DC Area

Christopher Hough

Member, Paleontological Society of Washington

From the Coastal Plain to the eastern edge of the Tectonic Plate(s) of Eastern North America, an amateur’s collection of marine invertebrate fossils tells an intriguing natural history that we all pass every day on our way to work. Taking advantage of the well –eroded stream beds of northeastern DC area and the foresight of the National Area Park and Planning Commission to preserve them as they are, I have collected a sampling of corals spanning the late Pre-Cambrian to the late Cretaceous. Though the collection is spotty from the perspective of diversity, it tells an interesting story of what went on during that time.

Non-Smithsonian visitors will be escorted from the Constitution Ave. entrance of the NMNH to the Q?rius auditorium at 6:50 and 6:55 p.m. Society members will host the speaker for dinner at the Elephant & Castle (1201 Pennsylvania Ave.) prior to the meeting. Members may meet at the restaurant or inside the Constitution Ave. entrance of the NMNH at 5:00 and walk to the restaurant as a group. Parking is available in the west side parking lot of the NMNH.

PGS: W and L’s Conners on Alaskan tectonics

November 16th, 2017 Meeting
Willow Room, DoubleTree Hotel, Tysons Corner, Va.
Located at 1960 Chain Bridge Rd., McLean, VA 22102

Social: 6:00-7:00 PM O’Malley’s Pub
Dinner: 7:00- 8:15 PM Willow Room, 2nd floor DoubleTree Hotel
Presentation: Begins at 8:15 PM Willow Room, 2nd floor DoubleTree

Chris Conners, PhD
Washington and Lee University

Subsurface Expression of the Tectonic History of Arctic Alaska and Adjacent Beaufort and Chukchi Seas

If you wish to attend dinner ($30 members; $40 non-members), please inform us via email at . Or if you wish, please feel free to attend only the talk without dinner. Non-members and guests are always welcome. To obtain more details
about the meeting and society, please visit our website at:

UMD: Georgetown’s Johnson on “Life on Mars” (+ distant moons)

2017 Geology Colloquium Series at the University of Maryland, College Park
Friday, November 3rd 2017 at 3:00 pm
in PLS 1130
Sarah Johnson
Georgetown University
Searching for Life on Mars and Distant Moons
Advances in molecular biology have the potential to alter the way we look for life in solar system, from direct detections to a deeper understanding of how biology affects patterns of mineralization. This talk will discuss our ongoing research into biosignature detection, including work in planetary analog environments like Australian acid salt lakes and the Dry Valleys of Antarctica. It will explore how handheld sequencers are starting to change the way we do remote field work, and how one day they may transform biological observation of the most inaccessible places on Earth, just as remotely telemetered image data revolutionized our understanding of the planet at the dawn of the Space Age. The talk will conclude with possibilities for nanopore-based life detection, including a concept that harnesses the power of sequencing to fingerprint patterns of surface chemical complexity as signatures of life, regardless of whether that life is based on nucleic acids.