Scientists discover carbonate rocks are unrecognized methane sink

Since the first undersea methane seep was discovered 30 years ago, scientists have meticulously analyzed and measured how microbes in the seafloor sediments consume the greenhouse gas methane as part of understanding how the Earth works.

The sediment-based microbes form an important methane “sink,” preventing much of the chemical from reaching the atmosphere and contributing to greenhouse gas accumulation. As a byproduct of this process, the microbes create a type of rock known as authigenic carbonate, which while interesting to scientists was not thought to be involved in the processing of methane.

That is no longer the case. A team of scientists has discovered that these authigenic carbonate rocks also contain vast amounts of active microbes that take up methane. The results of their study, which was funded by the National Science Foundation, were reported today in the journal Nature Communications.

“No one had really examined these rocks as living habitats before,” noted Andrew Thurber, an Oregon State University marine ecologist and co-author on the paper. “It was just assumed that they were inactive. In previous studies, we had seen remnants of microbes in the rocks – DNA and lipids – but we thought they were relics of past activity. We didn’t know they were active.

“This goes to show how the global methane process is still rather poorly understood,” Thurber added.

Lead author Jeffrey Marlow of the California Institute of Technology and his colleagues studied samples from authigenic compounds off the coasts of the Pacific Northwest (Hydrate Ridge), northern California (Eel River Basin) and central America (the Costa Rica margin). The rocks range in size and distribution from small pebbles to carbonate “pavement” stretching dozens of square miles.

“Methane-derived carbonates represent a large volume within many seep systems and finding active methane-consuming archaea and bacteria in the interior of these carbonate rocks extends the known habitat for methane-consuming microorganisms beyond the relatively thin layer of sediment that may overlay a carbonate mound,” said Marlow, a geobiology graduate student in the lab of Victoria Orphan of Caltech.

These assemblages are also found in the Gulf of Mexico as well as off Chile, New Zealand, Africa, Europe – “and pretty much every ocean basin in the world,” noted Thurber, an assistant professor (senior research) in Oregon State’s College of Earth, Ocean, and Atmospheric Sciences.

The study is important, scientists say, because the rock-based microbes potentially may consume a huge amount of methane. The microbes were less active than those found in the sediment, but were more abundant – and the areas they inhabit are extensive, making their importance potential enormous. Studies have found that approximately 3-6 percent of the methane in the atmosphere is from marine sources – and this number is so low due to microbes in the ocean sediments consuming some 60-90 percent of the methane that would otherwise escape.

Now those ratios will have to be re-examined to determine how much of the methane sink can be attributed to microbes in rocks versus those in sediments. The distinction is important, the researchers say, because it is an unrecognized sink for a potentially very important greenhouse gas.

“We found that these carbonate rocks located in areas of active methane seeps are themselves more active,” Thurber said. “Rocks located in comparatively inactive regions had little microbial activity. However, they can quickly activate when methane becomes available.

“In some ways, these rocks are like armies waiting in the wings to be called upon when needed to absorb methane.”

The ocean contains vast amounts of methane, which has long been a concern to scientists. Marine reservoirs of methane are estimated to total more than 455 gigatons and may be as much as 10,000 gigatons carbon in methane. A gigaton is approximate 1.1 billion tons.

By contrast, all of the planet’s gas and oil deposits are thought to total about 200-300 gigatons of carbon.

Scientists discover carbonate rocks are unrecognized methane sink

Since the first undersea methane seep was discovered 30 years ago, scientists have meticulously analyzed and measured how microbes in the seafloor sediments consume the greenhouse gas methane as part of understanding how the Earth works.

The sediment-based microbes form an important methane “sink,” preventing much of the chemical from reaching the atmosphere and contributing to greenhouse gas accumulation. As a byproduct of this process, the microbes create a type of rock known as authigenic carbonate, which while interesting to scientists was not thought to be involved in the processing of methane.

That is no longer the case. A team of scientists has discovered that these authigenic carbonate rocks also contain vast amounts of active microbes that take up methane. The results of their study, which was funded by the National Science Foundation, were reported today in the journal Nature Communications.

“No one had really examined these rocks as living habitats before,” noted Andrew Thurber, an Oregon State University marine ecologist and co-author on the paper. “It was just assumed that they were inactive. In previous studies, we had seen remnants of microbes in the rocks – DNA and lipids – but we thought they were relics of past activity. We didn’t know they were active.

“This goes to show how the global methane process is still rather poorly understood,” Thurber added.

Lead author Jeffrey Marlow of the California Institute of Technology and his colleagues studied samples from authigenic compounds off the coasts of the Pacific Northwest (Hydrate Ridge), northern California (Eel River Basin) and central America (the Costa Rica margin). The rocks range in size and distribution from small pebbles to carbonate “pavement” stretching dozens of square miles.

“Methane-derived carbonates represent a large volume within many seep systems and finding active methane-consuming archaea and bacteria in the interior of these carbonate rocks extends the known habitat for methane-consuming microorganisms beyond the relatively thin layer of sediment that may overlay a carbonate mound,” said Marlow, a geobiology graduate student in the lab of Victoria Orphan of Caltech.

These assemblages are also found in the Gulf of Mexico as well as off Chile, New Zealand, Africa, Europe – “and pretty much every ocean basin in the world,” noted Thurber, an assistant professor (senior research) in Oregon State’s College of Earth, Ocean, and Atmospheric Sciences.

The study is important, scientists say, because the rock-based microbes potentially may consume a huge amount of methane. The microbes were less active than those found in the sediment, but were more abundant – and the areas they inhabit are extensive, making their importance potential enormous. Studies have found that approximately 3-6 percent of the methane in the atmosphere is from marine sources – and this number is so low due to microbes in the ocean sediments consuming some 60-90 percent of the methane that would otherwise escape.

Now those ratios will have to be re-examined to determine how much of the methane sink can be attributed to microbes in rocks versus those in sediments. The distinction is important, the researchers say, because it is an unrecognized sink for a potentially very important greenhouse gas.

“We found that these carbonate rocks located in areas of active methane seeps are themselves more active,” Thurber said. “Rocks located in comparatively inactive regions had little microbial activity. However, they can quickly activate when methane becomes available.

“In some ways, these rocks are like armies waiting in the wings to be called upon when needed to absorb methane.”

The ocean contains vast amounts of methane, which has long been a concern to scientists. Marine reservoirs of methane are estimated to total more than 455 gigatons and may be as much as 10,000 gigatons carbon in methane. A gigaton is approximate 1.1 billion tons.

By contrast, all of the planet’s gas and oil deposits are thought to total about 200-300 gigatons of carbon.

Extinct undersea volcanoes squashed under Earth’s crust cause tsunami earthquakes, according to new

New research has revealed the causes and warning signs of rare tsunami earthquakes, which may lead to improved detection measures.

Tsunami earthquakes happen at relatively shallow depths in the ocean and are small in terms of their magnitude. However, they create very large tsunamis, with some earthquakes that only measure 5.6 on the Richter scale generating waves that reach up to ten metres when they hit the shore.

A global network of seismometers enables researchers to detect even the smallest earthquakes. However, the challenge has been to determine which small magnitude events are likely to cause large tsunamis.

In 1992, a magnitude 7.2 tsunami earthquake occurred off the coast of Nicaragua in Central America causing the deaths of 170 people. Six hundred and thirty seven people died and 164 people were reported missing following a tsunami earthquake off the coast of Java, Indonesia, in 2006, which measured 7.2 on the Richter scale.

The new study, published in the journal Earth and Planetary Science Letters, reveals that tsunami earthquakes may be caused by extinct undersea volcanoes causing a “sticking point” between two sections of the Earth’s crust called tectonic plates, where one plate slides under another.

The researchers from Imperial College London and GNS Science in New Zealand used geophysical data collected for oil and gas exploration and historical accounts from eye witnesses relating to two tsunami earthquakes, which happened off the coast of New Zealand’s north island in 1947. Tsunami earthquakes were only identified by geologists around 35 years ago, so detailed studies of these events are rare.

The team located two extinct volcanoes off the coast of Poverty Bay and Tolaga Bay that have been squashed and sunk beneath the crust off the coast of New Zealand, in a process called subduction.

The researchers suggest that the volcanoes provided a “sticking point” between a part of the Earth’s crust called the Pacific plate, which was trying to slide underneath the New Zealand plate. This caused a build-up of energy, which was released in 1947, causing the plates to “unstick” and the Pacific plate to move and the volcanoes to become subsumed under New Zealand. This release of the energy from both plates was unusually slow and close to the seabed, causing large movements of the sea floor, which led to the formation of very large tsunami waves.

All these factors combined, say the researchers, are factors that contribute to tsunami earthquakes. The researchers say that the 1947 New Zealand tsunami earthquakes provide valuable insights into what geological factors cause these events. They believe the information they’ve gathered on these events could be used to locate similar zones around the world that could be at risk from tsunami earthquakes. Eyewitnesses from these tsunami earthquakes also describe the type of ground movement that occurred and this provides valuable clues about possible early warning signals for communities.

Dr Rebecca Bell, from the Department of Earth Science and Engineering at Imperial College London, says: “Tsunami earthquakes don’t create massive tremors like more conventional earthquakes such as the one that hit Japan in 2011, so residents and authorities in the past haven’t had the same warning signals to evacuate. These types of earthquakes were only identified a few decades ago, so little information has been collected on them. Thanks to oil exploration data and eyewitness accounts from two tsunami earthquakes that happened in New Zealand more than 70 years ago, we are beginning to understand for first time the factors that cause these events. This could ultimately save lives.”

By studying the data and reports, the researchers have built up a picture of what happened in New Zealand in 1947 when the tsunami earthquakes hit. In the March earthquake, eyewitnesses around Poverty Bay on the east coast of the country, close to the town of Gisborne, said that they didn’t feel violent tremors, which are characteristic of typical earthquakes. Instead, they felt the ground rolling, which lasted for minutes, and brought on a sense of sea sickness. Approximately 30 minutes later the bay was inundated by a ten metre high tsunami that was generated by a 5.9 magnitude offshore earthquake. In May, an earthquake measuring 5.6 on the Richter scale happened off the coast of Tolaga Bay, causing an approximate six metre high tsunami to hit the coast. No lives were lost in the New Zealand earthquakes as the areas were sparsely populated in 1947. However, more recent tsunami earthquakes elsewhere have devastated coastal communities.

The researchers are already working with colleagues in New Zealand to develop a better warning system for residents. In particular, new signage is being installed along coastal regions to alert people to the early warning signs that indicate a possible tsunami earthquake. In the future, the team hope to conduct new cutting-edge geophysical surveys over the sites of other sinking volcanoes to better understand their characteristics and the role they play in generating this unusual type of earthquake.

Extinct undersea volcanoes squashed under Earth’s crust cause tsunami earthquakes, according to new

New research has revealed the causes and warning signs of rare tsunami earthquakes, which may lead to improved detection measures.

Tsunami earthquakes happen at relatively shallow depths in the ocean and are small in terms of their magnitude. However, they create very large tsunamis, with some earthquakes that only measure 5.6 on the Richter scale generating waves that reach up to ten metres when they hit the shore.

A global network of seismometers enables researchers to detect even the smallest earthquakes. However, the challenge has been to determine which small magnitude events are likely to cause large tsunamis.

In 1992, a magnitude 7.2 tsunami earthquake occurred off the coast of Nicaragua in Central America causing the deaths of 170 people. Six hundred and thirty seven people died and 164 people were reported missing following a tsunami earthquake off the coast of Java, Indonesia, in 2006, which measured 7.2 on the Richter scale.

The new study, published in the journal Earth and Planetary Science Letters, reveals that tsunami earthquakes may be caused by extinct undersea volcanoes causing a “sticking point” between two sections of the Earth’s crust called tectonic plates, where one plate slides under another.

The researchers from Imperial College London and GNS Science in New Zealand used geophysical data collected for oil and gas exploration and historical accounts from eye witnesses relating to two tsunami earthquakes, which happened off the coast of New Zealand’s north island in 1947. Tsunami earthquakes were only identified by geologists around 35 years ago, so detailed studies of these events are rare.

The team located two extinct volcanoes off the coast of Poverty Bay and Tolaga Bay that have been squashed and sunk beneath the crust off the coast of New Zealand, in a process called subduction.

The researchers suggest that the volcanoes provided a “sticking point” between a part of the Earth’s crust called the Pacific plate, which was trying to slide underneath the New Zealand plate. This caused a build-up of energy, which was released in 1947, causing the plates to “unstick” and the Pacific plate to move and the volcanoes to become subsumed under New Zealand. This release of the energy from both plates was unusually slow and close to the seabed, causing large movements of the sea floor, which led to the formation of very large tsunami waves.

All these factors combined, say the researchers, are factors that contribute to tsunami earthquakes. The researchers say that the 1947 New Zealand tsunami earthquakes provide valuable insights into what geological factors cause these events. They believe the information they’ve gathered on these events could be used to locate similar zones around the world that could be at risk from tsunami earthquakes. Eyewitnesses from these tsunami earthquakes also describe the type of ground movement that occurred and this provides valuable clues about possible early warning signals for communities.

Dr Rebecca Bell, from the Department of Earth Science and Engineering at Imperial College London, says: “Tsunami earthquakes don’t create massive tremors like more conventional earthquakes such as the one that hit Japan in 2011, so residents and authorities in the past haven’t had the same warning signals to evacuate. These types of earthquakes were only identified a few decades ago, so little information has been collected on them. Thanks to oil exploration data and eyewitness accounts from two tsunami earthquakes that happened in New Zealand more than 70 years ago, we are beginning to understand for first time the factors that cause these events. This could ultimately save lives.”

By studying the data and reports, the researchers have built up a picture of what happened in New Zealand in 1947 when the tsunami earthquakes hit. In the March earthquake, eyewitnesses around Poverty Bay on the east coast of the country, close to the town of Gisborne, said that they didn’t feel violent tremors, which are characteristic of typical earthquakes. Instead, they felt the ground rolling, which lasted for minutes, and brought on a sense of sea sickness. Approximately 30 minutes later the bay was inundated by a ten metre high tsunami that was generated by a 5.9 magnitude offshore earthquake. In May, an earthquake measuring 5.6 on the Richter scale happened off the coast of Tolaga Bay, causing an approximate six metre high tsunami to hit the coast. No lives were lost in the New Zealand earthquakes as the areas were sparsely populated in 1947. However, more recent tsunami earthquakes elsewhere have devastated coastal communities.

The researchers are already working with colleagues in New Zealand to develop a better warning system for residents. In particular, new signage is being installed along coastal regions to alert people to the early warning signs that indicate a possible tsunami earthquake. In the future, the team hope to conduct new cutting-edge geophysical surveys over the sites of other sinking volcanoes to better understand their characteristics and the role they play in generating this unusual type of earthquake.

Panama Canal, Panama City at risk of large earthquake, says new research

Satellite image showing location of Panama canal.
Satellite image showing location of Panama canal.

New data suggest that the Limon and Pedro Miguel faults in Central Panama have ruptured both independently and in unison over the past 1400 years, indicating a significant seismic risk for Panama City and the Panama Canal, according to research published today by the Bulletin of the Seismological Society of America (BSSA).

The Panama Canal is undergoing expansion to allow for greater traffic of larger ships, scheduled for completion by 2014. As part of a seismic hazard characterization for the Panama Canal Authority (ACP) expansion project, Rockwell, et al., studied the geologic and geomorphic expression of the Pedro Miguel, Limon, and related faults, followed by an in-depth study into their earthquake and displacement history, critical factors in the design of the Panama Canal new locks and associated structures.

“The Pedro Miguel fault actually runs between the existing Pacific locks – the Pedro Miguel and Miraflores locks – and last ruptured in a large earthquake in 1621,” said lead author Thomas K. Rockwell, professor of geology at San Diego State University. “That earthquake resulted in nearly 10 feet of displacement where the fault crosses the canal, and a similar amount of offset of the historical Camino de Cruces, the old Spanish cobblestone road that was used to haul South American gold across the isthmus. Another such earthquake today could have dramatic effects.”

The Republic of Panama sits atop two colliding tectonic plates — Central and South America — and is internally deforming at a significant rate. The Pedro Miguel, Limon and related faults comprise a zone that extends from the southern flank of the Sierra Maestra in north central Panama southward for at least 40 km (about 25 miles) crossing the Panama Canal between the Miraflores and Pedro Miguel Locks, and extending southward offshore into the Gulf of Panama.

Paleoseismic work by Rockwell, et al., demonstrates that both the Limon and Pedro Miguel faults are seismically active, having a relatively short recurrence rate for large earthquakes, with displacements in the range of 1.5 to 3 meters (4.9 to 9.8 feet). The oldest event on the Pedro Miguel fault is estimated at 455 AD and is older than any of the events recorded for the Limon fault. However, the penultimate Pedro Miguel event and the third Limon fault event identified in this study have very similar ages at about 700 AD and may represent rupture of the entire onshore zone.

The apparent ability for these two distinct faults to fail in unison has important implications for Panama Canal. While no fault passes through or beneath any critical structures, the area and structures would be subject to significant shaking. The authors note that the close proximity of Panama City to this active fault zone, and the lack of consideration of earthquake loads in structural design codes, puts this area at high seismic risk, particularly before current buildings can be replaced with stronger, more earthquake-resistant construction.

New satellite maps of Haiti coming in

This is a damage evaluation map based on satellite data over the Port-au-Prince area of Haiti, following a 7.0 magnitude earthquake and several aftershocks that hit the Caribbean nation on 12 January. Map based on data from CNES's SPOT-5, JAXA's ALOS and the US-based GeoEye-1 satellites; this was processed by SERTIT. -  CNES, JAXA, GeoEye, SERTIT
This is a damage evaluation map based on satellite data over the Port-au-Prince area of Haiti, following a 7.0 magnitude earthquake and several aftershocks that hit the Caribbean nation on 12 January. Map based on data from CNES’s SPOT-5, JAXA’s ALOS and the US-based GeoEye-1 satellites; this was processed by SERTIT. – CNES, JAXA, GeoEye, SERTIT

As rescue workers scramble to provide assistance to hundreds of thousands of people following Haiti’s earthquake, Earth observation satellite data continues to provide updated views of the situation on the ground.

Following the 7.0-magnitude earthquake that hit Haiti on 12 January, international agencies requested satellite data of the area from the International Charter on ‘Space and Major Disasters’.

The Charter, an international initiative aimed at providing satellite data free of charge to those affected by disasters anywhere in the world, immediately began re-tasking their satellites to get the data urgently needed.

Data are being collected by various satellites including Japan’s ALOS, CNES’s Spot-5, the U.S.’s WorldView and QuickBird, Canada’s RADARSAT-2, China’s HJ-1-A/B and ESA’s ERS-2 and Envisat.

These data are being processed into maps that show the degree of destruction. As soon as new data arrives, updated maps will be produced and made available to the international community.

Haiti quake occurred in complex, active seismic region




The Haiti earthquake epicenter is marked by the star along the displaced portion (shown in red) of the Enriquillo-Plantain Garden Fault. The 7.0 magnitude quake struck along about one-tenth of the 500-km-long strike-slip fault. The region sits on a complex  seismic area made up of numerous faults and plates. The fault lines with small arrows denote a different kind of fault called thrust faults, where one plate dives under another. Strike-slip faults grind past one another. The dotted lines at bottom denote complex seafloor formations. (Source: Jansma, P. and Mattioli, G., 2005, GPS results from Puerto Rico and the Virgin Islands: constraints on tectonic setting and rates of active faulting, Geol. Soc. Amer. Spec. Paper 385 (ed. Paul Mann), 13-30.)
The Haiti earthquake epicenter is marked by the star along the displaced portion (shown in red) of the Enriquillo-Plantain Garden Fault. The 7.0 magnitude quake struck along about one-tenth of the 500-km-long strike-slip fault. The region sits on a complex seismic area made up of numerous faults and plates. The fault lines with small arrows denote a different kind of fault called thrust faults, where one plate dives under another. Strike-slip faults grind past one another. The dotted lines at bottom denote complex seafloor formations. (Source: Jansma, P. and Mattioli, G., 2005, GPS results from Puerto Rico and the Virgin Islands: constraints on tectonic setting and rates of active faulting, Geol. Soc. Amer. Spec. Paper 385 (ed. Paul Mann), 13-30.)

The magnitude 7.0 earthquake that triggered disastrous destruction and mounting death tolls in Haiti this week occurred in a highly complex tangle of tectonic faults near the intersection of the Caribbean and North American crustal plates, according to a quake expert at the Woods Hole Oceanographic Institution (WHOI) who has studied faults in the region and throughout the world.

Jian Lin, a WHOI senior scientist in geology and geophysics, said that even though the quake was “large but not huge,” there were three factors that made it particularly devastating: First, it was centered just 10 miles southwest of the capital city, Port au Prince; second, the quake was shallow-only about 10-15 kilometers below the land’s surface; third, and more importantly, many homes and buildings in the economically poor country were not built to withstand such a force and collapsed or crumbled.

All of these circumstances made the Jan. 12 earthquake a “worst-case scenario,” Lin said. Preliminary estimates of the death toll ranged from thousands to hundreds of thousands. “It should be a wake-up call for the entire Caribbean,” Lin said.

The quake struck on a 50-60-km stretch of the more than 500-km-long Enriquillo-Plantain Garden Fault, which runs generally east-west through Haiti, to the Dominican Republic to the east and Jamaica to the west.

It is a “strike-slip” fault, according to the U.S. Geological Survey, meaning the plates on either side of the fault line were sliding in opposite directions. In this case, the Caribbean Plate south of the fault line was sliding east and the smaller Gonvave Platelet north of the fault was sliding west.

But most of the time, the earth’s plates do not slide smoothly past one another. They stick in one spot for perhaps years or hundreds of years, until enough pressure builds along the fault and the landmasses suddenly jerk forward to relieve the pressure, releasing massive amounts of energy throughout the surrounding area. A similar, more familiar, scenario exists along California’s San Andreas Fault.

Such seismic areas “accumulate stresses all the time,” says Lin, who has extensively studied a nearby, major fault , the Septentrional Fault, which runs east-west at the northern side of the Hispaniola island that makes up Haiti and Dominican Republic. In 1946, an 8.1 magnitude quake, more than 30 times more powerful than this week’s quake, struck near the northeastern corner of the Hispaniola.

Compounding the problem, he says, is that in addition to the Caribbean and North American plates, , a wide zone between the two plates is made up of a patchwork of smaller “block” plates, or “platelets”-such as the Gonvave Platelet-that make it difficult to assess the forces in the region and how they interact with one another. “If you live in adjacent areas, such as the Dominican Republic, Jamaica and Puerto Rico, you are surrounded by faults.”

Residents of such areas, Lin says, should focus on ways to save their lives and the lives of their families in the event of an earthquake. “The answer lies in basic earthquake education,” he says.

Those who can afford it should strengthen the construction and stability of their houses and buildings, he says. But in a place like Haiti, where even the Presidential Palace suffered severe damage, there may be more realistic solutions.

Some residents of earthquake zones know that after the quake’s faster, but smaller, primary, or “p” wave hits, there is usually a few-second-to-one-minute wait until a larger, more powerful surface, or “s” wave strikes, Lin says. P waves come first but have smaller amplitudes and are less destructive; S waves, though slower, are larger in amplitude and, hence, more destructive.

“At least make sure you build a strong table somewhere in your house and school,” said Lin. When a quake comes, “duck quickly under that table.”

Lin said the Haiti quake did not trigger an extreme ocean wave such as a tsunami, partly because it was large but not huge and was centered under land rather than the sea.

The geologist says that aftershocks, some of them significant, can be expected in the coming days, weeks, months, years, “even tens of years.” But now that the stress has been relieved along that 50-60-km portion of the Enriquillo-Plantain Garden Fault, Lin says this particular fault patch should not experience another quake of equal or greater magnitude for perhaps 100 years.

However, the other nine-tenths of that fault and the myriad networks of faults throughout the Caribbean are, definitely, “active.”

“A lot of people,” Lin says, “forget [earthquakes] quickly and do not take the words of geologists seriously. But if your house is close to an active fault, it is best that you do not forget where you live.”

Geologists to help communicate the dangers of Colombian volcano

During the past decade, residents of Pasto, Colombia, and neighboring villages near Galeras, Colombia’s most dangerous volcano, have been threatened with evacuation, but compliance varies. With each new eruption — the most recent explosion occurred June 7-9 — Colombian officials have grown increasingly concerned about the safety of the residents who live within striking distance of Galeras, located 700 km from Bogota.

Now, geologists from the University at Buffalo and the Universidad de Nariño have organized a special workshop in Colombia designed to tackle the communication issue, with support from the National Science Foundation and the Universidad de Nariño.

The purpose is to develop a consensus as to how best to raise awareness and protect these communities from dangerous eruptions at Galeras.

Unlike most scientific workshops, which are exclusively attended by scientists, this program will include the active participation of local residents and government officials working together with the scientists in all of the workshop sessions.

From July 6-11, Michael F. Sheridan, Ph.D., an internationally renowned volcanologist and director of UB’s Center for Geohazards Studies, and Gustavo Cordoba, Ph.D., a post-doctoral researcher in the UB center, will run the workshop on “Knowledge Sharing and Collaboration in Volcanic Risk Mitigation at Galeras Volcano, Colombia.” Complete information is at http://galerasworkshop09.weebly.com/index.html.

The first half of the workshop, which will feature professors from the UB Department of Geology, the Universidad de Nariño in Colombia, officials from the local and federal government and the Red Cross, among others, will cover the history of volcanic eruptions at Galeras, volcanic crisis management, the physics and modeling of explosive volcanism and discussions about crisis management at Soufriere Hills Volcano, Chaiten Volcano,Vesuvius and others.

The second half of the workshop will begin July 10 with a session called “The People Speak.”

Sheridan said that this part of the workshop puts a spotlight on the critical connection between local populations affected by an adjacent hazard and the level of scientific understanding and certainty — or the lack of it — about that hazard.

“The villagers feel they are safe,” said Sheridan.

In one example, he said, some of them have said that there is a sacred stone with petroglyphs on it that lies directly in the path where volcanic debris is expected to flow, but it has been there for 500 years and has never been damaged by eruptions at Galeras.

The workshop will use the example of a bridge that connects a village in the region (La Florida) to the capitol city Pasto, a city of 400,000 located only six miles from the crater of Galeras.

“Using our computational tools, we will show that if mudflows from this volcano inundate the bridge, then the evacuation route will be gone,” he said.

At the workshop, scientists, officials and residents will analyze existing hazard maps and safety plans for Galeras in light of the latest research on forecasting volcanic hazards.

“Our hope is that through the presentations by scientists and crisis management experts about what has happened at other volcanoes, and by using some visual tools, like computational modeling of mud and debris flows, we can help people living around the volcano better understand the hazard they live with,” said Sheridan.

With decades of experience all over the globe, working with scientists, governments and local populations, Sheridan concedes that it will be a challenge to try to improve the residents’ preparedness by attempting to better communicate how vulnerable they may be to eruptions at Galeras.

Still, he says that that goal will ultimately ease the job of volcanologists and others involved with risk mitigation.

“I’d like to see the workshop end with a new approach to hazards that includes the opinions of the people who are actually living in the hazard location,” he said. “It may be too much to hope for, but if it’s possible to get them to buy into the safety plan, that would be the best outcome.”

New monitoring stations detect ‘silent earthquakes’ in Costa Rica

After installing an extensive network of monitoring stations in Costa Rica, researchers have detected slow slip events (also known as “silent earthquakes”) along a major fault zone beneath the Nicoya Peninsula. These findings are helping scientists understand the full spectrum of motions occurring on the fault and may yield new insights into the events that lead to major earthquakes.

A slow slip event involves the same fault motion as an earthquake, but it happens so slowly that the ground does not shake. It can be detected only with networks of modern instruments that use the Global Positioning System (GPS) to measure precisely the movements of the Earth’s crust over time.

Susan Schwartz, a professor of Earth and planetary sciences at the University of California, Santa Cruz, leads a team that has installed a permanent network of 13 GPS monitoring stations and 13 seismic stations on Costa Rica’s Nicoya Peninsula.

“At least two slow slip events have occurred beneath the Nicoya Peninsula since 2003,” Schwartz said. “When we recorded the first one in 2003, we had only 3 GPS stations. By 2007, we had 12 GPS stations and over 10 seismic stations, so the event that year was very nicely recorded.”

The National Science Foundation (NSF) has funded the work by Schwartz and others to install monitoring equipment in Costa Rica. Schwartz, who directs UCSC’s Keck Seismological Laboratory, has been working in the region since 1991. At the annual meeting of the American Association for the Advancement of Science (AAAS) in Chicago, she will describe results from the past decade of fault-zone monitoring in Central America.

“The newest discovery is the occurrence of these slow slip events. But there has been a decade of focused effort in this area that has significantly advanced our knowledge of the Central America seismogenic system,” Schwartz said. “Initially, we focused on areas of the fault that are locked up, which slip in an earthquake. The slow slip is occurring in regions that are not strongly locked, and a big question is whether that is loading the locked area, making it more likely to break, or relieving stress on the fault.”

Schwartz said she does not think slow slip events significantly increase the likelihood of a major earthquake on a locked portion of the fault. She noted, however, that scientists are still at an early stage in terms of understanding the implications of different kinds of fault motion and translating that information into earthquake hazard assessments.

Flanked by active tectonic margins on both the Pacific and Caribbean coasts, Costa Rica is one of the most earthquake-prone and volcanically active countries in the world. Just off the west coast is the Middle America Trench, where a section of the seafloor called the Cocos Plate dives beneath Central America, generating powerful earthquakes and feeding a string of active volcanoes. This type of boundary between two converging plates of the Earth’s crust is called a subduction zone–and such zones are notorious for generating the most powerful and destructive earthquakes.

The slow slip phenomenon was first observed at subduction zones where hundreds of GPS and seismic instruments are deployed: the Cascadia fault zone (off the coast of Washington and British Columbia) and Japan’s Nankai Trough. At these and most other subduction zones, the part of the plate boundary where earthquakes originate, called the seismogenic zone, lies beneath the ocean. But in Costa Rica, the seismogenic zone runs right beneath the Nicoya Peninsula.

“It’s a perfect opportunity to study the seismogenic zone using a network of land-based instruments,” Schwartz said.

The 2007 slow slip event in Costa Rica involved movement along the fault equivalent to a magnitude 6.9 earthquake. But it took place over a period of 30 days rather than the 10 seconds typical for an earthquake of that size, and such slow motion does not radiate the seismic energy associated with normal earthquakes. The instruments did pick up seismic tremor, however, which Schwartz likened to a lot of very small earthquakes. Tremor activity is also associated with slow slip events in Japan and Cascadia, but there are some differences in Costa Rica, Schwartz said.

“Costa Rica has a different type of subduction zone from the well-studied ones in Japan and Cascadia,” she said. “One thing that makes it interesting is that the temperature is much cooler at the depth range where slip occurs, and that is helping us work out the role of fluids in generating slow slip.”

Ultimately, the goal of this research is not only a better understanding of subduction zones, but also better assessments of earthquake hazards. Schwartz said her Costa Rican colleagues have been working to educate the population of Nicoya about earthquakes and related hazards. With a growing population along the coast, the region faces a potential tsunami threat as well as the possibility of a major earthquake, she said.

Isthmus of Panama formed as result of plate tectonics





Paleogeographic reconstructions of Central America for (A) 20 Ma and (B) 15 Ma.
Paleogeographic reconstructions of Central America for (A) 20 Ma and (B) 15 Ma.

Contrary to previous evidence, a new University of Florida study shows the Isthmus of Panama was most likely formed by a Central American Peninsula colliding slowly with the South American continent through tectonic plate movement over millions of years.



The study, co-authored by Florida Museum of Natural History researchers Michael Kirby, Douglas Jones and Bruce MacFadden, is published in the July 30 issue of PLoS ONE, the online journal of the Public Library of Science. The study uses geologic, chemical and biologic methods to date rocks and fossils found in sides of the Gaillard Cut of the Panama Canal. The results show that instead of being formed by rising and subsiding ocean levels or existing as a string of islands as scientists previously believed, the Isthmus of Panama was first a peninsula of southern Central America before the underlying tectonic plates merged it with South America 4 million years ago.



“Scientists knew Panama was a North American peninsula, possibly as early as 19 million years ago because fossils that are closely related to North American land mammals, such as rhinos, horses, peccaries and dogs have been found in the Panama Canal during ongoing maintenance,” said Kirby, lead author of the study. “But we were not certain when this peninsula first formed and how long it may have existed.”



The canal’s maintenance also exposes sediment layers and marine animal fossils, as well as strata of rocks and clay specific to numerous environments, including lagoon, delta, swamp, woodland and dry tropical forest.



Previous studies placed marine sediment as the youngest layers, suggesting the peninsula was submerged before finally joining with South America. The current study revises the time order of strata, however, and concludes that the Panamanian peninsula joined with South America roughly 4 million years ago.



Deep-sea deposits in one sediment layer suggest a short-lived strait may have existed across the Panama Canal Basin between 21 and 20 million years ago,” said Jones, director of the Florida Museum of Natural History. “However, these short-lived straits probably had little impact on the long-term evolution of Central America’s flora and fauna.”


Kirby explained that because of numerous geologic faults resulting from tectonic plate movement that continues today, there is no area in Panama that allows a full view of the strata making up the land.



“We realized there was a problem with our previous understanding of the stratigraphy, or layering of sediments, in Panama,” Kirby said.



The authors used alternative methods such as strontium isotope dating of fossils and re-analysis of vertebrate fossils to better determine the geologic sequence of the Canal.



“There’s always missing information, like pages out of a book, when it comes to figuring out which layers came first and which were formed later,” Kirby added.



Anthony Coates, a staff scientist emeritus at the Smithsonian Tropical Research Institute in Panama who has extensively studied the geological history of the rise of the Central American isthmus, said the study brings together a diverse array of geologic evidence that convincingly suggests Central America was a peninsula and not a group of islands.



“They have made an important contribution to the land-based geologic evidence of the plate tectonic history of the formation of the Isthmus,” said Coates, who did not participate in the study. “Their results have important consequences for the nature of the global change engendered by the rise and closure of the isthmus.”



One of the major effects of the formation of the Isthmus of Panama was the intensification of the Gulf Stream in the Atlantic Ocean. While the area that is now Panama was still a peninsula, ocean currents moving north along the north coast of South America spilled over to the Pacific Ocean through the wide Central American Seaway, also called the Atrato Seaway. As tectonic plate movement joined the peninsula with South America to form the present-day Isthmus of Panama, equatorial ocean currents between the Atlantic and Pacific were cut off, forcing water northward into the Gulf Stream current.



“The strengthened Gulf Stream, in turn, delivered enough moisture to allow the formation of glaciers across North America,” Kirby said.



The complete text of the study is available on the publication’s Web site, www.plosone.org/doi/pone.0002791.