History Of Quaternary Volcanism And Lava Dams In Western Grand Canyon

Daily Science Journal (Feb. 11, 2008) — John Wesley Powell wrote in 1895: “...what a conflict of water and fire there must have been [in western Grand Canyon]! Just imagine a river of molten rock running down over a river of melted snow.”

Toroweap Point in Grand Canyon national park. (Credit: iStockphoto/Natalia Bratslavsky)

Over 110 years later, a synthesis of new and existing dates on these lava flows shows that many are significantly younger than initially thought and all are less than 725 thousand years old. The geochronology data indicates four major episodes when lava flows either erupted into the canyon or flowed over the rim into it: 725-475 thousand years ago (ka), 400-275 ka, 225-150 ka, and 150-75 ka.

These flows formed lava dams in western Grand Canyon that had dramatic impact on the Colorado River.

This paper* presents light detection and ranging (lidar) data to establish the elevations of the tops and bottoms of basalt flow remnants along the river corridor. These data show the original extent of now-dissected intra-canyon flows and aid in correlation of flow remnants.

From 725 to 475 ka, volcanism built a high edifice within Grand Canyon in the area of the Toroweap fault, with dike-cored cinder cones on both rims and within the canyon itself. These large-volume eruptions helped drive the far-traveled basalt flows which flowed down-canyon over 120 km. A second episode of volcanism, from 400 to 275 ka, built a 215-m-high dam along the Hurricane fault, about 15 km downstream.

The ca. 200 and 100 ka flows (previously mapped as Gray Ledge) were smaller flows and lava cascades that entered the canyon from the north rim between the Toroweap and Hurricane faults.

The combined results suggest a new model for the spatial and temporal distribution of volcanism in Grand Canyon in which composite lava dams and edifices were generally leaky in proximal areas.

Available data suggest that the demise of volcanic edifices may have involved either large outburst-flood events or normal fluvial deposition at times when the river was established on top of basalt flows. These data highlight complex interactions of volcanism and fluvial processes in this classic locality.

This research, authored by Ryan Crow (University of New Mexico) et al. was published in the February issue of Geosphere, published by the Geological Society of America.

Adapted from materials provided by Geological Society of America.

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Making Accurate Predictions Of Tsunami Risks

Daily Science Journal (Feb. 2, 2008) — A new review of tsunami hazards concludes that the 2004 catastrophe was far from the worst possible in many Indian Ocean borderlands - and notes that warning systems to guard at-risk populations are still lagging.

Wave patterns generated by an earthquake just west of the Indonesian island of Sumatra. (Credit: Image courtesy of University of Southern California)

Costas Synolakis, director of the University of Southern California Tsunami Research Center is co-author of "Far-Field Tsunami Hazard From Mega-Thrust Earthquakes in the Indian Ocean," just published in the Geophysical Journal International.

Synolakis and co-author Emile Okal of Northwestern University evaluated all known potential tsunami-generating sources in the vast area between Africa, Asia, Australia and Antarctica, and then calculated the impact of the tsunamis they can generate, should they rupture. Their paper presents the geographical distribution of risk.

The pair examined eight scenarios, two along Southern Sumatra (in Indonesia), two in the North Andaman segment of the Sumatra Subduction Zone, two sources along the Makran Subduction Zone (south of western Pakistan) and two sources south of Java. (Indonesia)

According to Synolakis, a professor in the USC Viterbi School of Engineering's Sonny Astani Department of Civil and Environmental Engineering, "the most important lesson from the scenarios we investigated is that the patterns of far-field maximum amplitudes predicted by our simulations will not be a repeat of those observed in 2004." The differences result from differences in the directions in which the disturbances propagate, "and in many instances the results are counterintuitive."

Synolakis expressed high confidence in the reliability of the projections. "Even if the earthquakes, as they materialize in the future, have geometric characteristics that are slightly different from our hypothetical scenarios, the far field impact projections are robust to small initial perturbations arising from uncertainty in the rupture characteristics."

Among the paper's conclusions:

• The impact in the mid-ocean Maldive Islands from all scenarios appears to be similar or less than what was observed in 2004 - however the low-lying structure of the islands makes them more difficult to evacuate than other risk sites..
• The impact in Madagascar and the Mascarene Islands (Mauritius, Rodrigues and Réunion) and the Seychelles could be far greater than in 2004, particularly from earthquakes in Southern Sumatra and in South Java. Madagascar is found particularly vulnerable from South Sumatran tsunamis.
• Africa suffered in excess of 300 deaths in 2004, 300 of them in Somalia. Its east coast is vulnerable from south Sumatran tsunamis and in particular, Somalia remains at high risk due to the focusing effect of the Maldives ridge. The Comoro islands located between Tanzania and Madagascar would probably be affected more severely than in 2004.
• Large earthquakes in south Java would generate substantial levels of destruction in Northern Australia, despite the sparse level of development there.
• The Strait of Malacca area appears more vulnerable than in 2004, from earthquakes in the North Andaman. Bali and Lombok and could be severely affected by large events in south Java. In fact Bali was affected by the 1994 tsunami, whose trigger was smaller than the ones envisioned here.
• The Kerguelen Islands (49.5◦S; 69.5◦E), part of the French Southern and Antarctic Territories, are highly vulnerable. Other than the North Andaman scenarios, practically all other events affect the Kerguelens, where apparently the 2004 tsunami did not cause damage. The much larger offshore heights the simulations predict would put the scientific base there (60-100 persons) at risk

Many of these scenarios have never been examined before. Synolakis' USC colleague Jose Borrero and others examined the local impact from south Sumatran scenarios in a 2006 paper in the Proceedings of the National Academy of Sciences. Synolakis and Okal concentrated on basin-wide impacts not studied earlier.

The impact to the eastern coast of India and in Myanmar and Bangladesh from the North Andaman scenarios was examined in a paper recently published in Nature by Phil Cummins (2007) of Geoscience Australia. The impact the new paper predicts is slightly different, Synolakis says, but only in the geographical distribution of the carnage.

According to that paper, the Makran Coast of Baluchistan constitutes a subduction zone along which the Arabian plate sinks under the Eurasian one. This was the site of a major earthquake on 1945 November 27, which was accompanied by a significant regional tsunami, with run-up in the five to ten meter range.

Synolakis and Okal, who is a professor in Northwestern's Department of Earth and Planetary Science, examined different rupture scenarios and their affect on the Makran coast, Oman and the west coast of India. "They are substantial and need more detailed study," Synolakis said, making reference to a documented catastrophe that occurred 24 centuries ago: "While the tsunami impact could be inferred from Pliny's reports of the adventure sof the fleet of Alexander the Great returning from India at the Straits of Hormuz in 434 AD, it has not yet been examined to the extent it deserves given the commercial and military value of the Straits.

Synolakis and Okal agree with Cummins about a critical need for the area: a warning net.

"It is quite clear that a tested and true tsunami early warning system as now works in the Pacific by the Pacific Tsunami Warning Center needs to be urgently implemented in the Indian Ocean," said Synolakis. "This system should include hundreds of pre-computed detailed scenarios of inundation for all Indian Ocean nations to facilitate emergency planning for evacuation should any of these scenarios materialize. Public education is a must and local people and visitors should be made aware of tsunami hazards, no matter how unlikely they may be, just us Hawaii and Oregon are already doing."

Synolakis and Okal began work on the project almost in the immediate aftermath of Sumatra 2004 and was completed last year.

"Our work was triggered from three different two week classes we taught for UNESCO in 2006/2007 on tsunami hazard mitigations in the Indian Ocean," said Synolakis. "More than eighty professionals attended having been nominated by their governments and we tried to show them how to assess with us the local impact from adjacent sources. We tried to guide them towards understanding and evaluating transoceanic impact, but the computational tools they had then were just not optimal.

"The work we present here extends the synthesis of hundreds of inundation projections done by our students in these classes, with varying degrees of success. However, all the specific scenarios we used are the synthesis of extensive literature and archive review, a synthesis of the preliminary material we developed in the UNESCO classes and of course all the computations are new."

The National Science Foundation and the European Union - via a Transfer Grant - supported the research.

Adapted from materials provided by University of Southern California.

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Innovative Method Improves Tsunami Warning Systems, Offers New Insights

ScienceDaily (Jan. 29, 2008) — A wave of new NASA research on tsunamis has yielded an innovative method to improve existing tsunami warning systems, and a potentially groundbreaking new theory on the source of the December 2004 Indian Ocean tsunami.

Using GPS data (purple arrows) to measure ground displacements, scientists replicated the December 2004 Indian Ocean tsunami, whose crests and troughs are shown here in reds and blues, respectively. The research showed GPS data can be used to reliably estimate a tsunami's destructive potential within minutes. (Credit: NASA/JPL)

In one study, published last fall in Geophysical Research Letters, researcher Y. Tony Song of NASA's Jet Propulsion Laboratory, Pasadena, Calif., demonstrated that real-time data from NASA's network of global positioning system (GPS) stations can detect ground motions preceding tsunamis and reliably estimate a tsunami's destructive potential within minutes, well before it reaches coastal areas. The method could lead to development of more reliable global tsunami warning systems, saving lives and reducing false alarms.

Conventional tsunami warning systems rely on estimates of an earthquake's magnitude to determine whether a large tsunami will be generated. Earthquake magnitude is not always a reliable indicator of tsunami potential, however. The 2004 Indian Ocean quake generated a huge tsunami, while the 2005 Nias (Indonesia) quake did not, even though both had almost the same magnitude from initial estimates. Between 2005 and 2007, five false tsunami alarms were issued worldwide. Such alarms have negative societal and economic effects.

Song's method estimates the energy an undersea earthquake transfers to the ocean to generate a tsunami by using data from coastal GPS stations near the epicenter. With these data, ocean floor displacements caused by the earthquake can be inferred. Tsunamis typically originate at undersea boundaries of tectonic plates near the edges of continents.

"Tsunamis can travel as fast as jet planes, so rapid assessment following quakes is vital to mitigate their hazard," said Ichiro Fukumori, a JPL oceanographer not involved in the study. "Song and his colleagues have demonstrated that GPS technology can help improve both the speed and accuracy of such analyses."

Song's method works as follows: an earthquake's epicenter is located using seismometer data. GPS displacement data from stations near the epicenter are then gathered to derive seafloor motions. Based upon these data, local topography data and new theoretical developments, a new "tsunami scale" measurement from one to 10 is generated, much like the Richter Scale used for earthquakes. Song proposes using the scale to make a distinction between earthquakes capable of generating destructive tsunamis from those unlikely to do so.

To demonstrate his methodology on real earthquake-tsunamis, Song examined three historical tsunamis with well-documented ground motion measurements and tsunami observations: Alaska in 1964; the Indian Ocean in 2004; and Nias Island, Indonesia in 2005. His method successfully replicated all three. The data compared favorably with conventional seismic solutions that usually take hours or days to calculate.

Song said many coastal GPS stations are already in operation, measuring ground motions near earthquake faults in real time once every few seconds. "A coastal GPS network established and combined with the existing International GPS Service global sites could provide a more reliable global tsunami warning system than those available today," he said.

The theory behind the GPS study was published in the December 20 issue of Ocean Modelling. Song and his team from JPL; the California Institute of Technology, Pasadena, Calif.; University of California, Santa Barbara; and Ohio State University, Columbus, Ohio, theorized most of the height and energy generated by the 2004 Indian Ocean tsunami resulted from horizontal, not vertical, faulting motions. The study uses a 3-D earthquake-tsunami model based on seismograph and GPS data to explain how the fault's horizontal motions might be the major cause of the tsunami's genesis.

Scientists have long believed tsunamis form from vertical deformation of seafloor during undersea earthquakes. However, seismograph and GPS data show such deformation from the 2004 Sumatra earthquake was too small to generate the powerful tsunami that ensued. Song's team found horizontal forces were responsible for two-thirds of the tsunami's height, as observed by three satellites (NASA's Jason, the U.S. Navy's Geosat Follow-on and the European Space Agency's Environmental Satellite), and generated five times more energy than the earthquake's vertical displacements. The horizontal forces also best explain the way the tsunami spread out across the Indian Ocean. The same mechanism was also found to explain the data observed from the 2005 Nias earthquake and tsunami.

Co-author C.K. Shum of Ohio State University said the study suggests horizontal faulting motions play a much more important role in tsunami generation than previously believed. "If this is found to be true for other tsunamis, we may have to revise some early views on how tsunamis are formed and where mega tsunamis are likely to happen in the future," he said.

Adapted from materials provided by NASA/Jet Propulsion Laboratory.

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2004 Sumatra Tsunami And Storm-generated Waves On North America's Atlantic Coast Were Concurrent

Daily Science Journal (Aug. 16, 2007) — The Sumatra-Andaman earthquake generated a catastrophic tsunami that caused heavy damage and fatalities in coastal areas around the Indian Ocean. The tsunami, which struck on 26 December 2004, also propagated throughout the world's oceans, making it the first such event to be scrutinized with continuous observations of widespread oceanic monitoring networks.

Thomson et al. analyze more than 100 tide gauge records from the Atlantic coast of North America and find that the tsunami was identified in most outer tide gauges from Florida to Nova Scotia. Maximum heights for northern regions were between 32 and 39 centimeters (1.0 and 1.3 feet), while southern regions experienced wave heights between 15 and 33 centimeters (0.49 and 1.1 feet).

However, along the shores of Maine and Nova Scotia, the arrival of the tsunami coincided with the presence of tsunami-like waves generated by a major storm tracking northward along the U.S. eastern seaboard. The combined waves reached heights in excess of 1 meter (3.3 feet).

The authors warn that, although the northern Atlantic Ocean has low tsunami hazards, tsunamis from distant seismic events could threaten coastal infrastructure and habitat when the waves coincide with winter storm waves.

Title: Double jeopardy: Concurrent arrival of the 2004 Sumatra tsunami and storm-generated waves on the Atlantic coast of the United States and Canada

Authors: Richard E. Thomson: Institute of Ocean Sciences, Sidney, British Columbia, Canada;

Alexander B. Rabinovich: Institute of Ocean Sciences, Sidney, British Columbia, Canada; also at P.P. Shirshov Institute of Oceanology, Moscow, Russia;

Maxim V. Krassovski: School of Earth and Ocean Sciences, University of Victoria, Victoria, British Columbia, Canada.

Source: Geophysical Research Letters (GRL) paper 10.1029/2007GL030685, 2007

Adapted from materials provided by American Geophysical Union, via EurekAlert!, a service of AAAS.

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Satellite Tracking Will Help Answer Questions About Penguin Travels

Daily Science Journal (Aug. 10, 2007) — You could understand if a half-dozen Magellanic penguins developed a "big bird is watching" phobia before this month is over, but the surveillance really will be for their own good.

The feathers of three Magellanic penguins blackened with oil, seen along Argentina's Atlantic coast in October 2005. (Credit: Dee Boersma)

University of Washington scientists will attach satellite tracking devices to the backs of six penguins that have been treated at two centers in northern Argentina after their feathers were fouled with oil. The birds will be released into the Atlantic Ocean and their movements traced using satellites and the Internet.

The idea is to plug a critical gap in the knowledge of the Magellanics' annual life cycle, their movements on the journey from their winter feeding grounds back to their breeding colonies along the southern Argentina coast and the Islas Malvinas, or Falkland Islands.

"We're missing that information. We know what happens when they leave the breeding grounds but we don't know what happens on the return trip," said Elizabeth Skewgar, a University of Washington doctoral student in biology.

"We want to model the energy requirements for these birds so that we understand what it takes to return to the breeding grounds and still have enough energy to reproduce. Human fisheries competing for the same food could make migration even more difficult for them."

The project is led by Dee Boersma, a UW biology professor who for 25 years has headed the Magellanic Penguin Project at Punta Tombo, Argentina, the birds' largest breeding colony in South America.

"We need to know how penguins use the ocean so we can make their migration route safe through a combination of national marine parks, marine protected areas and ocean zoning," Boersma said.

During the week of Aug. 20, the scientists will select six adult male penguins from rehabilitation centers at San Clemente del Tuyu and Mar del Plata, coastal towns more than 500 miles north of Punta Tombo. Epoxy and special tape will be used to attach a transmitter to each bird before it is released into the Atlantic. The tags are about the size of many common cellular telephones and weigh less than 3.5 ounces.

"We want to put the transmitters on healthy, robust birds that we think are likely to get back and start breeding," Boersma said. "The point is to follow them back to their colony and see where they might be running into petroleum."

Through late October the birds' movements will be tracked by the Argos satellite system, operated by the National Oceanic and Atmospheric Administration and the French space agency. A satellite will pass overhead every two hours and chart the penguins' positions, then transmit the information back to the researchers, who will use it to update a public tracking map on the Internet at http://www.penguinstudies.org.

The transmitters will be active for 36 hours at a time and then will be off for 36 hours, a means of preserving the two double-A batteries in each transmitter for the life of the project. The researchers have no way of knowing whether the birds will go to southern Argentina or the Malvinas, or whether they will follow a straight course to the breeding grounds or take a circuitous route.

"After we release them, they could just hang out at Mar del Plata for a month. It's all up to them," Boersma said. "We're hoping the males we tag will be in a hurry to get to their colony and start breeding."

The satellite tracking also will be instrumental in pinpointing the birds after they arrive at the breeding grounds. Punta Tombo alone is home to some 400,000 penguins during breeding season.

"Tracking the locations by satellite is only accurate to within 5 kilometers, so it really is like trying to find a needle in a haystack," Boersma said.

Locating the penguins once they reach the breeding ground is important so the researchers can assess the birds' physical condition after the long journey.

"We'll know how much weight they gained or lost on their journey," Boersma said.

After its mate arrives, a male fasts until the female lays two eggs, then he returns to the ocean to feed, sometimes swimming hundreds of miles in search of fish such as anchovies that are staples of the penguin diet. After about two weeks the male returns to the nest to incubate the eggs while the female goes in search of food.

The birds' energy can be drastically sapped if they become coated with oil, and that can mean death. Last year, a team of scientists that included Boersma reported they had found 19 groups rehabilitating oiled seabirds along the Atlantic coast from central Brazil to central Argentina, indicating a much larger problem than generally had been believed. It remains uncertain where the oil comes from -- it could be from a combination of sources, including seepage from offshore oil rigs and ballast water from passing ships.

"We know that birds show up oiled back at our colony, so that means they're getting oiled somewhere between where they winter and Punta Tombo," Boersma said.

Others involved in the work are Sergio Rodriguez Heredia of the Fundacion Mundo Marino in San Clemente del Tuyu, Karen Griot of Fundacion Mar del Plata Aquarium and Valeria Ruoppolo of the International Fund for Animal Welfare's Penguin Network.

The research will be included in Skewgar's doctoral dissertation. The work is being funded by the Wildlife Conservation Society, with support from the tourism office of the Argentine Province of Chubut.

Adapted from materials provided by University of Washington.

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