Draft Minutes for the 1521st meeting of the Geological Society of Washington

October 4th, 2017

John Wesley Powell Auditorium, Cosmos Club, Washington, D.C.

President Bentley called to order the 49 attendees of the 1520th meeting to order at 20:02 EDT with all the vigor befitting a man carrying a Budweiser gavel.

The minutes of the 1519th meeting were approved with no corrections having been read by an overwhelming minority of attending members. Again, no one uncovered the hidden Easter egg.

Guests, new members, deaths

Several guests were in attendance. The Society was honored with the presence of Rob Wallace – affiliation unknown, Amiga Thompson – NASA, Natalie Irwin – AGU, Robert Cohen – affiliation unknown, Megan Holycrus – NMNH, Arya Udry – UNLV (Go Rebels!), and David Smallwood, who still has not signed up for membership – DC Grotto.

There were five new members to announce. The Society was honored to have the following join the ranks: Barbara Cohen – NASA Goddard, Robert Wasserman – Environmental Chemical Corp., Bobbie Marcoux – NOVA Community College, Joseph Kanney – US Nuclear Regulatory Commission, and Adriana Potra – University of Arkansas.

After naming the new members, President Bentley assumed the somber duty of announcing the passings of former members, John Pojeta and Chuck Rice. President Bentley asked for a moment of silence, which the members observed.

Announcements and informal communiqués

There were no announcements or informal communications and President Bentley called to order the formal program.

Formal Program

The first presentation of the evening was given by Michael Ryan titled Columnar Jointing Mechanics in the Three Dimensions.

Inter-crystalline glass is ubiquitous in basalt, the common volcanic rock of earth’s ocean basins and oceanic islands. In Hawaii, eruption temperatures are in the 1190 – 1150 °C range and the solidus is reached at about 1000 – 980 °C. Inter-crystalline super cooled melt reaches the glass transition, Tg, at 750 °C, and subsequent cooling occurs in a high temperature mix of crystals and glass: a rheological, ‘sand-and-molasses’ mixture. Strong temperature gradients and ‘zero-displacement’ lateral boundary conditions conspire to set up thermal stresses in the cooling mass. The result is stress relief via elastic-plastic crack growth that is incremental and cyclic in time and space. This cyclic fatigue fracture is defined by abrupt elastic crack growth increments in the crystal + glass domain, and plastic crack tip blunting in the crystal + super cooled melt domain. The overall increment is preserved on the crack face as a fatigue striation. As the crack advances orthogonal to the isotherms, it (and neighboring cracks) collectively define polygonal columns in three dimensions. Under conditions of maximum local equilibrium, such polygons are hexagonal in plan form with faces meeting at 120 degree triple junctions. In forming the polygons, Nature strikes a balance between the maximum reduction in the thermally-induced elastic strain energy per unit volume and the creation of the minimum fracture surface area per unit volume. This (thermodynamic) balance occurs via cyclic fatigue fracture at the elastic-plastic interface.

Inquisitive minds, who stepped forward were Carl-Henry Geschwind – independent researcher, Partner of George Helz – UMD, Jamie Allan – NSF, Bill Burton – USGS, Pete Toulmin, Dan – beard, second row, glasses, right behind me and Patrick

The second talk of the evening was given by Christopher “Chuck” Bailey titled Normal Faulting and graben Development as catalysts for late Cenozoic landscape change, Fish Lake Plateau, UT

Sparked by the difference in summer time dew points, Dr. Bailey has long conducted field research in the western US. His recent work has focused on the Fish Lake Plateau. The Fish Lake Plateau forms a distinctive highland between the elevated Colorado Plateau, and the extended Basin & Range province in south-central Utah. Suites of normal faults and graben cut the Cenozoic to Mesozoic bedrock, and disrupt/modify regional to local drainage networks.Some faults are long-lived and deeply-rooted structures, whereas other faults and graben are shallow localized structures. In this talk, we’ll examine the links between deformation and landscape change during the late Cenozoic.

Questions were put forth by Carl-Henry Geschwind – 2nd VP and independent researcher, Bill Burton – USGS, Caitlin Sheza – affiliation unknown, Karn Prestigard, Victor Zabeilski – NOVA

The final talk of the evening was orated by Elizabeth McClellan titled Evolution of a Neoproterozoic Intracontinental Rift: New Insights from Provenance Analysis of Conglomerates in the Mount Rogers Formation, SW VA

Neoproterozoic volcano-sedimentary strata of the Mt. Rogers (MR) area in SW VA formed during a continental rifting phase of breakup of the Rodinia supercontinent. Geochronological analyses of igneous clasts in MR conglomerates reveal details of a more protracted history of this phase than previously understood.

Questions were asked by Bill Burton – USGS, Patrick Carr, Graham Lederer – USGS, Barbara Cohen – NASA, Chuck Bailey - UWM, and then Bill Burton, and then Chuck Bailey…

Upon the cessation of the back and forth between Bill and Chuck, President Bentley announced the program for the 1522nd meeting, and requested that members cajole friends and family to join them.

President Bentley adjourned the 1521st meeting of the Geological Society of Washington at 21:42 EDT.

Respectfully submitted,

Nik Deems

Meeting Secretary