"Heresy at Cambridge: Paleomagnetism before Vine and Matthews"

Gregory A. Good, Ph.D.
Director, Center for History of Physics
American Institute of Physics

Potomac Geophysical Society Meeting, October 15, 2009

The story of Fred Vine, Drummond Matthews, and sea-floor spreading is a well known part of the acceptance of plate tectonics in the 1960s. Vine and Matthews published their famous paper "Magnetic Anomalies over Oceanic Ridges" in Nature in 1963, but interest in paleomagnetism and continental drift in England started to rise as early as 1950 among a group of physicists and cosmologists there. These interlopers in geology -- Patrick Blackett, Teddy Bullard, and Keith Runcorn -- all had started in particle physics and cosmic ray research. How they ended up providing a basis for discovery in earth science traces an interesting tale of interdisciplinary research in the mid-20th century.

Greg is a historian of science who currently writes mostly about the history of geophysics and especially the history of geomagnetic research. He has degrees in both physics and in history of science and he taught in the History Department at West Virginia University from 1983 until 2008. He has been on the History Committee of the AGU since 1989 and is a member of GSA, the International Commission for the History of the Geological Sciences, and the History of Science Society. He has published many articles and two books, one on the geosciences at the Carnegie Institution of Washington and the other an encyclopedia of the history of the earth sciences. He edited the journal Earth Sciences History for the History of the Earth Sciences Society for six years. He was named a Fellow of the GSA this year, having received the Mary C. Rabbitt Award of the GSA Historical Division in 2008.

More information at the PGS website.

Labels: magnetism, meetings, pgs, plate tectonics

The September meeting of the Potomac Geophysical Society will be held September 17th at the Fort Myer Officers' Club in Arlington, VA in the Campaign Room. This month's talk will be: North Korean Nuclear Test of May 25 2009: Similarities and Differences With Respect to the Initial October 9, 2006 Test, by Jack Murphy (SAIC, McLean, VA).

Abstract:
On May 25, 2009 North Korea announced that it had conducted its second nuclear weapons test. As with the first test, this second explosion was well-detected by the seismic stations of the International Monitoring System (IMS), as well as numerous other international stations operated by the USGS and other organizations. The best relative seismic location for this explosion places it within 2 km of the ground truth location of the initial 2006 test in a mountainous region of northeastern North Korea. Comparisons of the seismic data recorded at common stations from these two tests indicate that the second was approximately four times larger than the first, having an estimated yield in the range from about 2 to 5 kt. While there are many similarities in the observations from the two tests, there are several notable differences. Perhaps the most surprising of these is that there were no reported detections from any of the IMS radionuclide stations. The report of a noble gas (Xe¹³³) detection in Canada tentatively associated with the October 2006 test had led to some optimism that the more complete network of stations operating in 2009 might provide powerful detection capability with respect to clandestine underground nuclear tests. While analyses are continuing, the absence of detections from the May 2009 test has tempered that optimism to some extent. Another unusual aspect of the May 2009 test was the observation of anomalously large long-period surface waves. While the surface waves from the October 2006 were also somewhat larger than expected, the surface wave Ms magnitude value for the May 2009 test places it in the earthquake population on the Ms:Mb discriminant plot, and there has been no convincing explanation offered for this to date. Thus, despite the many years of experience with nuclear test monitoring, there continue to be unanticipated surprises that require in-depth analyses and assessments.

Reception at 6:30. Dinner at 7:30. Talk at 8:30 PM. Allow 15 minutes for security entering Ft. Myer as all civilian vehicles are searched. To ensure access to and from Fort Myer use the Hatfield Gate, open 24 hours a day. If you wish to attend dinner ($25), please make reservations with Joydeep Bhattacharyya at 703-676-4373 or via e-mail. If you wish, please feel free to attend the talk without dinner. Non-members and guests are welcome. Visit the PGS web site at for new meeting announcements, etc.

Labels: earthquakes, korea, meetings, pgs

The April meeting of the Potomac Geophysical Society will be held April 16th at the Fort Myer Officers' Club in Arlington, VA in the Campaign Room. This month's talk will be: Mapping Rocks and Minerals using Advanced Spaceborne Thermal Emission and Reflection Radiometer data, by John 'Lyle' Mars (USGS, Reston, VA).

Abstract:
The Advanced Spaceborne Thermal Emission and Reflectance Radiometer (ASTER) measures reflected radiation in 3 bands in the 0.52 to 0.86 micrometer wavelength region (VNIR); 6 bands in the 1.6 to 2.43 micrometer wavelength region (SWIR); and 5 bands of emitted radiation in the 8.125 to 11.65 micrometer wavelength region (TIR) with 15-m, 30-m, and 90-m resolution, respectively. ASTER also has a backward-looking VNIR telescope with 15-m resolution. The swath-width is 60 km, but off-nadir pointing capability extends the total cross-track viewing of ASTER to 232 km. ASTER VNIR bands are positioned to delineate Fe absorption features, ASTER SWIR bands can delineate Al-OH, Fe Mg-OH, H-O-H and CO3 absorption features, and TIR bands are particularly useful for mapping Si-O vibrational features. This talk will demonstrate techniques and results of minerals and lithologic mapping using ASTER data. Mineral and lithologic maps compiled from ASTER data include parts of the western U.S., Afghanistan, Iran, Kazakhstan, Morocco, and Pakistan. Mapping algorithms include band ratio, matched filtering, and logical operators. Minerals and mineral groups mapped using ASTER data include, muscovite, argillic and phyllic-altered rocks, carbonate rocks, hydrothermal quartz, and quartz-rich rocks.

Biographical Information:
Lyle Mars is currently a Research Geologist in Remote Sensing at the USGS. He got his PhD from the University of Kentucky in 1995. His research is focused on gaining a better understanding of the spectral characteristics of a wide range of earth materials and how these characteristics are remotely sensed. This work is enhancing our abilities to identify important mineral resources, elucidate global tectonic relationships and facilitate recognition of environmental degradation related to mining. He investigates the spectral properties of rocks, minerals and vegetation and applies spectroscopic observations to research in multispectral and hyperspectral remote sensing studies. Most of his remote sensing projects are focused on spectral data in the 0.35 to 14.0 micrometer region. This research is applied to new remote sensing techniques in the identification of minerals, rock types, stratigraphy, structures, and vegetation. His spectroscopic research is also used in the calibration of new remote sensing systems such as the Advanced Spaceborne Thermal Reflection and Emission Radiometer (ASTER), Hyperion, and Hymap. Prior to USGS he was a Visiting Assistant Professor at George Mason University.

Reception at 6:30. Dinner at 7:30. Talk at 8:30 PM. Allow 15 minutes for security entering Ft. Myer as all civilian vehicles are searched. To ensure access to and from Fort Myer use the Hatfield Gate, open 24 hours a day. If you wish to attend dinner ($25), please make reservations with Joydeep Bhattacharyya at 703-676-4373 or via E-mail at Joydeep.bhattacharyya@saic.com. If you wish, please feel free to attend the talk without dinner. Non-members and guests are welcome. Visit the PGS web site for new meeting announcements, etc. Please send changes of address or email to Joydeep.bhattacharyya@saic.com.

Labels: minerals, pgs, satellite imagery

The March meeting of the Potomac Geophysical Society will be held March 19th at the Fort Myer Officers' Club in Arlington, VA in the Campaign Room. This month's talk will be: Geoarchaeology, Hydrology, and Wetland Morphology in the Belize Coastal Plain, by Sheryl Luzzadder-Beach (Assoc. Prof., George Mason University) and Timothy Beach (Professor, Georgetown University). Reception at 6:30. Dinner at 7:30. Talk at 8:30 PM.

Labels: belize, central america, pgs

The February meeting of the Potomac Geophysical Society will be held February 19th at the Fort Myer Officers' Club in Arlington, VA in the Campaign Room. This month's talk will be: Listening to a Melting Arctic Ocean - Singing the Blues?, by Peter N. Mikhalevsky, SAIC, VA.

Abstract:
The waters of the Arctic Ocean have been warming since the mid 1990's. Average maximum temperatures have risen by more than 1°C. In the last 20 years submarine measurements of sea ice draft have shown a 40% reduction in average sea ice thickness while satellite remote sensing has shown a 14% reduction in sea-ice extent over the same period decreasing at a rate of 3-5%/decade (thicker multi-year ice at 7-10%/decade). Forecasts indicate that if these trends continue the Arctic Ocean could be ice-free, "A Blue Arctic Ocean" before the end of this century. Significant effort is needed to expand our observational capabilities in the Arctic Ocean to support better modeling, forecasting and improve our understanding of this critical ocean and the linkages to global climate. One technique - acoustic thermometry - has been shown to be a very effective for monitoring average heat content and average temperature in the Arctic Ocean and in particular in the Arctic Intermediate Water (AIW) layer. Two experiments conducted in 1994 and 1999 measured the warming and demonstrated the feasibility of long term observations. Plans are in process to incorporate acoustic thermometry and tomography in in-situ Arctic Ocean observatories.

Dinner Menu
Chicken Marsala (House salad & vegetables, rolls and butter)
Tira Mi Su
Coffee / tea
A vegetarian meal can be substituted by request.

Reception at 6:30. Dinner at 7:30. Talk at 8:30 PM. Allow 15 minutes for security entering Ft. Myer as all civilian vehicles are searched. To ensure access to and from Fort Myer use the Hatfield Gate, open 24 hours a day (https://webmail-1.nvcc.edu/exchweb/bin/redir.asp?URL=http://www.fmmcmwr.com/directionsmyer.htm). If you wish to attend dinner ($25), please make reservations with Joydeep Bhattacharyya at 703-676-4373 or via E-mail at Joydeep.bhattacharyya@saic.com. If you wish, please feel free to attend the talk without dinner. Non-members and guests are welcome. Visit the PGS web site at https://webmail-1.nvcc.edu/exchweb/bin/redir.asp?URL=http://www.potomacgeophysical.com%2520/ for new meeting announcements, etc.

Labels: climate change, global warming, meetings, oceans, pgs

The January meeting of the Potomac Geophysical Society will be held January 15th at the Fort Myer Officers' Club in Arlington, VA in the Campaign Room.

This month's talk will be: How Deep Was That Earthquake?, by Jack Murphy, SAIC, McLean, VA.

Abstract:
Less than 100 years ago, seismologists were still actively debating whether deep earthquakes existed, and it wasn't until the 1920s that Turner in England and Wadati in Japan confirmed that some earthquakes do indeed occur at great depths below the surface of the Earth. We now know that, while the majority of earthquakes are shallow and confined to the Earth's crust, there are numerous earthquakes every year that occur at depths of hundreds of kilometers below the Earth's surface. Moreover, these deep earthquakes have played an important role in the development of our understanding of plate tectonics in that they mostly are confined to restricted zones along convergent plate boundaries, where their locations as functions of depth map out the trajectories of the descending slabs. However, despite the many improvements in computing power and analysis capability that have been introduced into earthquake location studies in recent years, it is still a challenge in many cases to accurately estimate the depth of an earthquake using commonly available seismological arrival time data. In this talk, the history of earthquake depth determination will be briefly reviewed and some recent research that has led to new approaches designed to address limitations of existing standard analysis procedures will be discussed.

Biographical Information:
Mr. Murphy is the Deputy Division Manager of the Monitoring Research Division of SAIC where he is responsible for managing research contracts with a variety of government agencies. He has had more than 40 years experience as a research seismologist and is an internationally recognized expert in the modeling and analysis of seismic signals produced by explosion and earthquake sources.

Labels: meetings, pgs

FYI, all you DC-metro-area-geophysicist types:

The October meeting of the Potomac Geophysical Society will be held October 16th at the Fort Myer Officers' Club in Arlington, Virginia in the Campaign Room. This month's talk will be: Infrasonic studies in the atmosphere using gravity wave models and a study of the 1988 PEPCON chemical explosion, by Dr. David Norris of Applied Physical Sciences.

Reception at 6:30. Dinner at 7:30. Talk at 8:30 PM. Allow 15 minutes for security entering Ft. Myer as all civilian vehicles are searched. To ensure access to and from Fort Myer use the Hatfield Gate. If you wish to attend dinner ($25), please make reservations with Joydeep Bhattacharyya at 703-284-1219 or via e-mail at jbhattac@bbn.com. If you wish, please feel free to attend the talk without dinner. Non-members and guests are welcome. Visit the PGS web site for new meeting announcements, etc.

Labels: meetings, pgs, virginia

Last night I attended my first meeting of the Potomac Geophysical Society (PGS). The PGS meets on Thursday nights, and I usually can't make it because I teach on Thursday nights. (I do however attend meetings of the Geological Society of Washington quite regularly, but those are on Wednesday nights.) Now that the semester is over, I was able to make it to the final PGS meeting of the spring.

The meeting was held at Fort Meyer Officer's Club. It's on a military base adjacent to Arlington National Cemetery, and before entering, my Prius had to be searched for bombs (as did all other civilian vehicles). The Officer's Club was about what you would expect, I guess -- kind of 1950's decor, elegant once. I noticed they had compact fluorescent light bulbs in all the sockets, which pleased me. PGS meetings consist of: (1) beer downstairs in the lounge, (2) dinner upstairs in the "Campaign Room," (3) business details, and (4) a talk by a guest speaker.

Last night's speaker was Bill Burton, from the USGS's volcano hazards and monitoring program. Bill's office will be launching a comprehensive new volcano website later this year, and he gave us a brief preview of its features in last night's talk. If you'd like a look for yourself, they have a beta version of the site online now.

Labels: gsw, meetings, pgs, volcano, websites