Newswise — NARRAGANSETT, R.I. – The following research will be presented by scientists at the University of Rhode Island’s Graduate School of Oceanography at the American Geophysical Union’s fall meeting in San Francisco from Dec. 9 to 13:
Earthquakes, landslides and tsunami hazards in the Greater AntillesPoster presentation: Dec. 11, 1:40 p.m., Moscone South, Hall A-C
The first deepwater exploration of the Greater Antilles region has changed our understanding of the geology and geological hazards of the area surrounding Puerto Rico and the Virgin Islands. Using remotely operated vehicles deployed from the Ocean Exploration Trust’s E/V Nautilus, the research team led by URI Marine Scientist Dwight Coleman, in collaboration with researchers from the U.S. Geological Survey, investigated several previously identified sources of seismic and tsunami hazards in the region to better understand their timing and activity. Examination of two wall scarps of the Mona landslide, previously believed to have caused a 1918 tsunami, showed the walls to be covered by manganese varnish, an indication that it was a much older landslide. The researchers found no evidence for the eastward continuation of the Septentrional Fault, the major fault stretching from Cuba through northern Hispaniola, into Mona Rift. This fault therefore may present a smaller seismic hazard to Puerto Rico than previously suggested. They also found no evidence of a fresh fault surface running from Desecheo Island into western Puerto Rico. The previously proposed fault trace of the 1867 Virgin Islands earthquake was found to be associated with a 30-meter high linear rock wall.
An additional possible fault, cut in places by landslide scars, was mapped by the ship’s multibeam echosounder close to St. Thomas, and could be associated with past earthquakes in the area. The suspected Noroît Seamount east of the Virgin Islands was mapped in detail and verified as being comprised of relatively young volcanic rock. If this volcano is part of the Lesser Antilles volcanic chain, then the Lesser Antilles chain extends almost to Barracuda Bank in the middle of Anegada Passage, where a steep landslide or fault trace was identified.
Derechos created meteorological tsunamis on East CoastPoster presentation: Dec. 10, 8 a.m., Moscone South, Hall A-C
When NOAA tide gauges from Maine to South Carolina recorded a small tsunami on June 13, 2013, doctoral student Christina Wertman investigated its cause, as well as that of similar phenomena that occurred along the East Coast in June 2012 and April 2013. After ruling out earthquakes or landslides as the cause of the waves that measured up to a half-meter in height, she concluded that the cause was weather-related. Meteorological tsunamis occur when an air pressure disturbance moves over the ocean, creating an interaction between the water and atmosphere that forces a shallow water wave. “They occur fairly commonly – within the last decade there have been about two per year – but they’re usually so small that most people don’t even notice them,” Wertman said. Because Wertman was able to track the air pressure disturbances back to their formation across the interior of the continental United States, she believes that these tsunamis can be predicted and monitored. She also found that, with each event, a second tsunami wave propagated back toward the shoreline after the first wave was reflected off the continental shelf break.
Ash from 1650 eruption of Kolumbo underwater volcano traveled twice previous estimatePresentation: Dec. 11, 2:25 p.m., Room 308, Moscone South When the Kolumbo underwater volcano last erupted in 1650 near the island of Santorini in the Aegean Sea, it spawned a tsunami, ash fallout in Turkey, and killed 70 people from its noxious gases. An examination of 60 boxcores from the seafloor in the vicinity of the eruption allowed graduate student Sarah Fuller to determine the extent of the ash deposits and how they got there. Fuller identified ash deposits from the eruption at least 19 kilometers from the caldera, more than twice the previous estimate. She also determined that the ash deposition occurred as a result of two types of sediment gravity flows – the collapse of the underwater eruption column, which occurs when the fine particles that are suspended in the water column collapse upon itself, and from a Rayleigh-Taylor instability, when ash in the atmosphere settles on the sea surface, causing an instability in the water column that leads to a rapid sinking of the ash. “This kind of information is important because it enhances our knowledge of volcano behavior,” said Fuller. “Kolumbo is in a very seismically active area, so this will help in modern day hazard mitigation planning.”
A model of hydrogen production in the oceanic basement – food for microbesPoster presentation: Dec. 9, 1:40 p.m., Moscone South, Hall A-C
When radioactive elements decay, ionizing radiation causes water molecules to split into oxygen and hydrogen, which microorganisms can use as a source of energy. This process, called water radiolysis, is helping scientists learn how microbial life may survive deep in the seafloor. Graduate student Mary Dzaugis developed a model to calculate how much hydrogen is produced through the radiolysis of water in the rock layer beneath the sediment in the South Pacific gyre. Analyzing samples of basalt rock collected in 2010, she found that the greatest yield of hydrogen occurred in the tiny fractures in the basalt where radioactive particles would come into contact with the most water. “This work is helping us understand the extent of life on Earth – the extreme pressures and temperatures that can still sustain life – which can help us understand how life first evolved here,” Dzaugis said. “And because there are similar environments on Mars and Europa, this research can be used as a model for potentially finding life on other planets.”
Surprising relationship between lavas erupting on the sea floor and the deep carbon cyclePresentation: Dec. 11, 8:30 a.m., Room 303, Moscone South
Katherine Kelley, associate professor of oceanography, and colleagues at the Smithsonian Institution will report on their discovery of unsuspected linkages between the oxidation state of iron in volcanic rocks and variations in the chemistry of the deep Earth. Their findings suggest that carbon plays a more significant role in the circulation of the deep Earth than had previously been predicted. “The relationships we’ve observed in basalts at mid-ocean ridges come about from the melting of Earth’s upper mantle, and it tells us about the chemistry and composition of Earth beneath ocean basins,” Kelley said. “We found a surprising relationship between the composition of lavas and the oxidation state of iron in the lavas.” The researchers used a microanalytical method called X-ray Absorption Near Edge Structure to analyze lava samples from mid-ocean ridges and found that carbon provides the means for exchanging oxygen and electrons with iron in the mantle, which is contrary to many years of previous research. “Carbon in Earth’s interior is impossible to measure directly, but it’s important that we know how much carbon there is because the volcanic flux of carbon out of Earth’s interior is a big variable in understanding how atmospheric CO2 is cycled through our planet,” Kelley said. “And that ties into our climate and the evolution of Earth.”
Understanding the evolution and natural selection of deep microbial lifePresentation: Dec. 10, 2:10 p.m., Room 2006 Moscone West
Oceanography Professor Steven D’Hondt, along with postdoctoral researcher John Kirkpatrick and graduate student Emily Walsh, are working with other scientists to census microbes that live deep below Earth’s surface. By conducting DNA analyses of microbes from sediments deep beneath the ocean floor, deep continental aquifers in South Africa, North America and Europe and elsewhere, they are discovering a fascinating network of subterranean microbial life. “There is widespread interest in learning whether there are unique organisms living down there, or whether it is dominated by organisms that are common at the surface,” said D’Hondt. “Are the same microorganisms found everywhere or is every subsurface ecosystem different? We’re mapping the geographic diversity of the subsurface world.” The URI team is working to understand the evolution and natural selection of subsurface microbes. By sampling microbial communities from different depths and comparing samples from beneath the Indian Ocean, the Bering Sea, the South Pacific and elsewhere, they have found that very few types of microbes last very long. “There doesn’t appear to be any single trait or characteristic that is key to survival in these challenging environments,” Kirkpatrick said. “If there were, there would be consistent winners and consistent losers, but the winners aren’t consistent and almost everything seems to be losing and getting wiped out. It’s remarkable that anything at all can survive under those conditions.”