Author Archives: Callan Bentley

Bentley to speak on local geology at Manassas library Sept. 15


​ The Mid-Atlantic region showcases two complete “Wilson cycles” of supercontinent formation and destruction. Though Virginia is mostly sedate today (occasional earthquakes notwithstanding), in the past the Old Dominion has been the site of Himalayan-scale mountain-building and rifting fully comparable to the Great Rift Valley of modern day East Africa. Award-winning NOVA geology professor Callan Bentley provides a fascinating tour of our region’s geologic history, looking at the modern landscape and interpreting these ancient tectonic events.

Tuesday, September 15, 2015, 7:00 p.m.

AEG/PGS: Conventional Tunneling at Tyson’s Corner

BWH Section of the Association of Environmental &

Engineering Geologists and the Potomac Geophysical Society

Date: Thursday May 21, 2015


Baltimore MD – Washington DC – Harrisburg PA

The Meeting will be held at the Amphora Restaurant, 377 Maple Ave., Vienna VA, 6:00-8:30pm. Reservations are necessary,  we need a head count for the restaurant, so, if you wish to attend dinner ($40, members; $45, non-members), please inform Bob Fraser by May 15th at 703-624-3965 (takes both voice and cell text messages) or via E-mail at Non-members and guests are welcome but must have a reservation. Let’s make this joint meeting a success: make a reservation!

TOPIC: Conventional Tunneling (SEM) at: Tysons Corner, Virginia

PRESENTER: Vojtech Gall, Ph.D., P.E. Gall Zeidler Consultants, Ashburn, VA

BIO: Dr. Gall is a Principal of Gall Zeidler Consultants, a tunnel engineering and consulting company headquartered in Northern Virginia. He has over twenty-five years of experience in the design, construction, and construction management of tunnels and underground structures. He frequently serves on expert review panels dedicated to the investigation and improvement of tunneling schemes ranging from initial inception stages through final design development at bid document level. His services relate to a wide variety of facilities ranging from hydro-power schemes in remote settings to complex transit structures at shallow overburden in difficult, over-built urban settings. He has led tunneling efforts on large infrastructure project such as Dulles Metrorail in DC, the Caldecott 4-th bore tunnel in San Francisco and the East Side Access project in New York City. He holds M.Sc. and B.Sc. degrees in Civil Engineering from the RWTH University in Aachen, Germany, a M.Sc. in Mineral Engineering from the University of Alabama and a Ph.D. in Civil Engineering from the University of Maryland. He is a registered Professional Engineer in 18 states and has authored over 40 technical publications on the subjects of tunneling.

ABSTRACT: The Metropolitan Washington Airports Authority (MWAA) is constructing the Dulles Corridor Metrorail Project (DCMP), which will extend Washington Metropolitan Area Transit Authority’s (WMATA) rail services from the Metrorail Orange Line in Fairfax County, Virginia to Route 772 near Ashburn in eastern Loudoun County, Virginia. The extension will be known as the Silver Line and once completed will add 23 miles to the existing Washington Metro System. The project was subdivided in two phases. Phase I segment is 12 miles long and involves 5 stations (two at grade and three elevated) and was opened to public in 2014. Phase II will extend the rail by another 11 miles with a station at Dulles International Airport and a terminus station in Ashburn.

Both phases use the design-build (DB) delivery method. Phase I was constructed by Dulles Transit Partners (DTP) a Joint Venture of Bechtel and URS and included twin 1,700 feet long single track, 22 feet diameter conventional tunnels (excavated by the Sequential Excavation Method or SEM) that are situated in the urban setting of Tysons Corner.

The presentation will address design and construction of these soft ground tunnels that emerged as the most feasible alternative to practically all other tunneling methods including open and closed face TBM drives and cut-and-cover techniques. Tunneling was accomplished with shallow overburden of as low as about 7 feet from the tunnel crown. Because of the shallow depth, soft ground conditions, and the need to control settlements, the tunnel design included use of a double row grouted pipe arch canopy as pre-support for the first 300 feet of excavation and a single row pipe arch canopy for the remaining length of tunnels thereafter. A real-time monitoring of the surface when tunneling the first 90 m under International Drive was implemented to assure VDOT of the tunneling performance.

USGS Mendenhall seminar: Mariana Islands seismicity & infrasound

Mendenhall Postdoctoral Research Seminar

John Lyons, USGS – Anchorage, AK

When: Monday, May 18, 2015 – 12 Noon

Where: Via WebEx and National Center, Room 3A409 (Chief Geologist’s Conference Room)


Long-period seismicity and infrasound driven by shallow magmatic degassing at Mount Pagan, Mariana Islands

Mount Pagan (570 m) is the currently active vent on the north end of Pagan Volcano, Mariana Islands.  Since the establishment of a monitoring network in 2013, a persistent degassing plume, long-period (LP) seismicity and infrasound, and infrequent small degassing explosions have dominated activity. The current low-level, open vent activity provides an ideal platform for studying the source processes of LP events, and how they relate to degassing. Many active volcanoes display LP (0.2-5 Hz) seismicity and because variations in LP activity often herald changes in eruption behavior, understanding the source mechanisms that generate LP events is a primary goal of volcano seismology. Expanding observations to include other data types greatly facilitates the interpretation of LP events. Studies correlating seismic and infrasound data have revealed important linkages between shallow LP seismicity and the generation of LP infrasound at other open vent, basaltic systems. Some form of degassing often accompanies LP activity, and integrating seismic and infrasound data with plume observations or gas chemistry allows further refinement of source models. In this study, we focus on characterizing the LP activity and interpreting the source processes generating the seismic and infrasonic signals through waveform modeling. The results are combined with gas emission and composition data and information about the shallow geologic structure to develop a model of shallow degassing for Mount Pagan.

WebEX Info

Topic: Mendenhall research Seminar
Date: Monday, May 18, 2015
Time: 11:00 am, Eastern Daylight Time (New York, GMT-04:00)
Meeting number: 714 351 061
Meeting password: (This meeting does not require a password.)
Host Key: 237217

Please verify the meeting topic above starts with the number of expected
connections, counting the presenter, for example:

Click the following link to view or edit your meeting information, or to start your meeting.

Teleconference: National Center in Reston, VA Dial In: x4848
DOI Dial In Number: 703-648-4848
Non-DOI Toll Free Dial In Number: 1-855-547-8255*
Security Code: 91930 followed by the # sign

Seth Burgess at USGS Reston: magmatism and mass extinctions

Special Seminar

Seth Burgess*, USGS – Menlo Park, CA

* Recipient of the 2014 Cozzarelli Prize (

When: Monday, April 27, 2015 – 11 AM

Where: Via WebEx and National Center, Room 1C400 (Visitor Center)


Using high-precision geochronology to test the link between magmatism and mass extinction

Broad temporal coincidence between select Phanerozoic instances of mass extinction and large igneous province (LIP) magmatism has led many to hypothesize a causal link between the two. Testing the plausibility of this connection depends on the tempo of both and their relative timing. Thus, dating the records of mass extinction and magmatism with the maximum possible precision and accuracy is critical. This presentation will detail the application of U/Pb thermal ionization mass spectrometry (TIMS) geochronology to (1) volcanic ash beds intercalated with the fossil record of the end-Permian mass extinction, and (2) lava flows, sills, and pyroclastic rocks of the Siberian Traps LIP. New dates permit a revised calculation of the tempo of magmatism and mass extinction and allow resolution of their relative timing.

WebEX Info

Topic: Mendenhall Fellow Talk: Seth Burgess

Date: Monday, April 27, 2015
Time: 10:30 am, Eastern Daylight Time (New York, GMT-04:00)
Meeting number: 719 125 959
Meeting password: (This meeting does not require a password.)
Host Key: 819447

Click the following link to view or edit your meeting information, or to start your meeting.

Teleconference: National Center in Reston, VA Dial In: x4848
DOI Dial In Number: 703-648-4848
Non-DOI Toll Free Dial In Number: 1-855-547-8255*
Security Code: 91930 followed by the # sign

May PSW meeting announcement

The Paleontological Society of Washington

Wednesday, May 20, 7:00 pm, in the Cooper room (E-207A), National Museum of Natural History, Constitutional Ave. entrance

Fossil Sea Cows (Mammalia: Sirenia) of Europe and the Mediterranean: Why So Depauperate?

Daryl Domning

Laboratory of Evolutionary Biology, Department of Anatomy, College of Medicine, Howard University, Washington D.C. 20059

Non-Smithsonian visitors will be escorted to the Cooper Room at 6:45 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 Constitutional Ave. entrance of the NMNH at 5:00 and walk to the restaurant as a group.

Spring Symposium, AEG-BWH, April 18 (Saturday)

Geologists and friends:

AEG-BWH is sponsoring a Spring Symposium on Saturday April 18, 2015. The Symposium will this year be held at James Madison University in Harrisonburg, VA. The theme of the Symposium is: The many facets of engineering geology

Our goal is to gather together leaders and students in geo-science, geo-engineering, and related disciplines to discuss their experiences with innovative methods (applied or research) being used in today’s projects. Our hope is that, through such gatherings, the AEG community will continue to grow and better serve to protect property and the environment.

We have a full-day program (see below) and offer 5 PDH’s.

My goal is to make the conference a yearly event. I hope to make it an opportunity for those universities with geology departments with an engineering bent to showcase their achievements.

For those students who wish to just attend the symposium, the cost is nominal ($20). Scholarships are available. Students making a presentation will have a scholarship. Others may be supported when recommended by their department professors.

Professional registration is $70. Contact:

Patrick Hastings
Seismic Surveys, Inc.
604 Solarex Court # 105
Frederick, MD 21703
Phone: (301) 663-6630

Below is the current program.

S. J. Stokowski, PG
Chairman, AEG-BWH
cell: 508-259-3536


Presentation Schedule:

8:30 am Registration
9:00-9:10 am Welcome & Introductions
9:10-9:35 am Steve Stokowski, TEC Services, “History and Geology of Aggregate Supply to Washington, DC”
9:35-10:00 am April Kelly, James Madison U, “Earthquake Detection in Central Virginia Using a Dual Template and Autocorrelation Method”
10:00 am BREAK
10:15-10:40 am Stephen Lane, VA Highway Res. Council., Application of Petrography to Highways
10:40-11:05 am Aida Farough, VA Tech, “Evolution Of Physical Properties Of Ultramafic Rocks At High Pressures And Variable Temperatures: Implications To Fault Zones”
11:05-11:30 am Jeremy Butcher, James Madison U, “Sediment source for Smith Creek, Shenandoah County, VA”
11:30-12:40 pm Poster Session and LUNCH (sandwiches and soft drinks included)
12:40 pm-1:00 pm Dr. Steve Whitmeyer, James Madison U. “Visualizing the Geology of Virginia Appalachians”.
1:00-1:25 pm Skip Watts, Radford U, “Do You Need More Geo In Your Geotechnical? Lessons Learned From Hydrogeology and Slope Stability”
1:25-1:50 pm, Louie, Timothy, James Madison U, “The Origins Of Late Silurian Cherts In The Sandstone Member Of The Tonoloway Formation In Bath County, VA”
1:50-215 pm Matt Heller, VA DMME, “Surface Exposure Dating of Debris Deposits in the Valley and Ridge Province, Rockingham County, VA”
2:15 pm BREAK
2:15-2:40 pm Elliott Andelman, James Madison U, “Pangea Breakup Revisited: A New Web Interface For Student Inquiry”
2:40-3:05 pm Dave Fenster, Bechtel Power, “Using Multiple Investigative Methods to Reduce Uncertainty in Karst Characterization”
3:05 -4:00 pm Mineral Museum
Poster Session (Noon)
Aida Farough, VA Tech, “An Experimental Study On Evolution Of Fracture Permeability Of Ultramafic Rocks Undergoing Serpentinization At Hydrothermal Conditions”
Kent Weidlich, Dylan Dwyer*, and Skip Watts, Radford U, “Potential Auxiliary Water Sources For Mountain Lake, Giles County, VA”
Dylan Dwyer, David Imberg*, and Skip Watts, Radford U, “Effects Of Terrain Modification On Surface Water Runoff From The Blueberry Cottages Watershed At Mountain Lake, Giles County, VA”
*Poster presenter

GSW Spring Field Trip: Karst

The 2015 GSW Spring field trip is scheduled for Saturday, May 2, 2015 and will be a cross section through karst areas of the Mid-Atlantic Piedmont to the Great Valley. This trip will start by looking at the intersection between karst and society by examining sinkhole development in the Wakefield Marble near New Market, Maryland, and within the Cambro-Ordovician limestones of the Frederick Valley at Frederick, Maryland. Next, a commercial cave tour of Crystal Grottoes in Boonsboro, Maryland (if possible). Spring-fed tufa, travertine, and marl soil development will be seen at Fairplay, Maryland. Caves and solutional features will be seen along the bluffs of the Potomac River within the C&O Canal National Park at McMahon’s Mill. Finally, karst topography will be discussed in relation to the epic Civil War battle fought at Antietam National Battlefield. 
Trip participants should congregate at the McDonald’s located at the New Market exit 62 off of I-70 in Maryland.  The trip will begin at 9 am and end at Antietam National Battlefield at dusk. Parking is not an issue, so multiple vehicles are permitted.