Bare Earth Elements: GSA highlights, days 2 and 3
CHARLOTTE, N.C. — EARTH’s Tim Oleson is in Charlotte, N.C., this week for the Geological Society of America’s (GSA) annual conference. He is blogging about interesting talks and activities he’s attended, so keep checking back to get the scoop. Read his first report from the conference here. You can also follow the action by following @earthmagazine on Twitter.
Monday and Tuesday at GSA are in the books here in Charlotte. Naturally, there were too many interesting presentations to attend, but that’s the beauty of conferences. What’s another great thing about them? In the same day: You can visit with undergraduate researchers like Nicole Finnegan of the College of St. Rose in Albany, N.Y., who along with her advisor is monitoring conditions in local streams. You can attend a talk given by a coral-reef-studying graduate student, Stephen Levas of Ohio State University, who collaborated with his wife, a high school teacher, to bring the science of reefs and the effects of climate change on them to ninth graders in an inner-city school in Columbus, Ohio. (They set up aquariums in the classroom and involved the students in monitoring efforts.) And you can listen to Jay Famiglietti, a renowned hydrogeologist at the University of California at Irvine who works with remote sensing data from the GRACE (Gravity Recovery and Climate Experiment) satellites, deliver an engaging yet sobering call-to-action regarding global groundwater redistribution and depletion in a warming world.
Of course, there were the hundreds of other talks and posters as well. Big themes were sea-level rise (as on Sunday), fracking, Mars, and geoscience education and outreach, among many others. Here’s a quick rundown of a few topics I found particularly interesting.
“How do you predict something that hasn’t happened?” asked geophysicist Uri ten Brink of the U.S. Geological Survey in Woods Hole, Mass., to begin his talk on Monday of possible tsunami hazards along the U.S. Atlantic Coast. Given the susceptibility of the coastline and its vast human-made infrastructure to severe flooding (ahem, does Sandy ring a bell?), it’s a very good question.
Ten Brink pointed out that there has been one recorded tsunami along the Atlantic Coast, albeit in Canada, in 1929. That event inundated the coast near the Grand Banks with a 3- to 8-meter wave that had a maximum run-up of 13 meters on land. Other than that, no other historical or pre-historical tsunamis are known to have doused our eastern shores. In the wake of other reminders, though, we’d probably be wise to keep in mind that nature loves to surprise us.
There are two potential sources for tsunamis, ten Brink said: offshore landslides that rapidly carry enormous sediment loads down the continental shelf, and “far-field” earthquakes in places like the Puerto Rico Trench or the Azores-Gibraltar plate boundary. A massive rupture on the latter led to the 1755 Lisbon tsunami that flooded much of the southern Portuguese coastline and, along with the earthquake and subsequent fires, nearly destroyed Lisbon. Thankfully, ten Brink reported, there is no evidence for an impending far-field earthquake capable of producing a tsunami large enough to affect the U.S. East Coast.
There is, however, evidence of numerous landslides off the coast during the geologically recent past. Looking at the record and size distribution of these past events, ten Brink said, shows that “landslides are mainly caused by earthquakes,” and that there is an apparent relationship between the size of the landslides and earthquake magnitude, as well as the stability of the slope on which the landslide forms.
Right now, ten Brink noted, there are still “more questions than answers” about the tsunami threat to the East Coast, but he did offer one comforting note: In order to cause a significant landslide — one capable of producing a potentially dangerous tsunami — an earthquake would have to be located within about 100 kilometers of the continental shelf. Because the continental shelf is farther than 100 kilometers offshore in most places, that finding basically rules out terrestrial earthquakes up and down most of the eastern portion of the country as potential causes.
In other East Coast-relevant earthquake and landslide news, Randall Jibson of the U.S. Geological Survey in Denver presented the results of a study on Tuesday morning showing that the magnitude-5.8 earthquake that struck central Virginia in August 2011 caused terrestrial rock falls and landslides over an area of about 33,400 square kilometers (albeit not on the continental shelf). The previous maximum area over which landslides were observed for a quake of this magnitude was just 1,500 square kilometers. Additionally, the Virginia earthquake, the largest on the east coast of the U.S. since 1897, spurred landslides at distances up to 245 kilometers from the epicenter, compared to the previous high of up to 60 kilometers for a similarly sized shaker.
CSG: Crime Scene Geology
In a session entitled “Progress in Forensic Geochemistry” on Monday, Elisa Bergslien of Buffalo State College spoke about the usefulness of analytical techniques such as inductively coupled plasma emission spectroscopy, atomic absorption spectroscopy and X-ray diffraction in identifying the authenticity of cremated remains. At least, that is, in telling whether remains are in fact animal in nature and not a fraudulent substitute.
As an example of how the techniques may be useful in deciphering the nature of cremated remains, Bergslien recounted the bizarre 2002 case of a Georgia crematory proprietor who was arrested and convicted after it was discovered that he had passed off distinctly nonhuman materials — concrete dust and wood ash, for example, as ashes to the families of deceased loved ones. (Instead of cremating 339 bodies, the proprietor had stored the bodies on crematory property.)
Calcium-to-phosphorus ratios and concentrations of elements such as titanium, zinc and strontium can be used to distinguish bones and teeth from other materials that might possibly be substituted, Bergslien said. Unfortunately, she noted, it is not yet possible to tell human bones from animal bones.
In another talk in the same session, George Kamenov of the University of Florida discussed the cold case of a woman whose body was recovered near Lake Pannasoffkee in Florida. Not much information about the identity of the woman — who came to be known as Little Miss Pannasoffkee — could be determined at the time, and the case went cold. Kamenov and his colleagues revisited the case this past spring, taking samples of hair, teeth and bone from the body. Analyses of oxygen, carbon, lead and strontium in the samples suggested that the woman was originally from southern Europe, possibly Greece, and had come to the U.S. within two months to a year before she died. Her true identity has still not been determined, but the research allowed for renewed efforts to track down Little Miss Pannasoffkee’s family. The case shows that such geo-referencing techniques can be very useful in helping provide new details in cold cases, Kamenov said.
Little Threat From Residual Fracking Fluids
As widespread apprehension over the environmental safety of shale gas-producing hydrofracturing operations continues, scientists have been trying to determine the various fates of water injected underground in the process. Much of this water stays underground for durations that outlast the lifetime of individual well sites, prompting concerns that it might later find its way into groundwater. In a Tuesday session devoted to studies related to water and hydrofracturing operations, specifically in the Marcellus Shale, Terry Engelder of Penn State suggested the threat of such upward migration of “fracking” wastewater known as residual treatment water was negligible for several reasons.
For one thing, noted Engelder, a specialist in rock mechanics and structural geology, there are no vertical pathways in the Marcellus sufficient to allow water to migrate upward freely, at least in areas where drilling is approved. Additionally, the prevailing capillary forces within the pore spaces of the shale — where the natural gas and water collect — and a process known as imbibition hold the treatment water (or water in general) in place in the pores rather than letting it escape easily. Although other hazards of fracking operations remain uncertain, “it is this natural imbibition that is going to assure the long-term sequestration of fracked fluid,” Engelder said. He added: “It ain’t gonna get out, folks.”