Earth Changes

New study says U.S. East Coast faces variety of tsunami threats

NEW YORK – Although the risk is small, tsunamis are possible on the East Coast of the United States from a variety of sources, according to new research. And as Hurricane Sandy showed, the region is completely unprepared for a major influx of water, said U.S. Geological Survey researcher Uri ten Brink. The most likely source for an East Coast tsunami would be an underwater avalanche along the continental slope, according to research presented by ten Brink and others earlier this month at the annual meeting of the Geological Society of America in Charlotte, N.C. Ten Brink also outlined several other possible sources of tsunamis, including earthquakes and even collapsing volcanoes. An offshore earthquake of magnitude 4.5 or above could cause submarine avalanches and create dangerous tsunamis with waves higher than 26 feet (8 meters), ten Brink told OurAmazingPlanet. Underwater canyons and bays could focus these waves and make them even bigger. A 7.2-magnitude earthquake off the southern coast of Newfoundland in 1929 caused a large underwater landslide, creating a large wave that rushed ashore and killed 28 people on the island, ten Brink said. The waves were up to 26 feet high until some reached narrow inlets, where they grew to 43 feet (13 m), he said. While the tsunami was catastrophic for Newfoundland, it created only small waves for most of the U.S. coast and didn’t cause any fatalities there. That’s typical of tsunamis from submarine landslides: They tend to be large for nearby areas but quickly taper off, ten Brink said. While this is the only example of a tsunami near the East Coast in recorded history, there are plenty of areas along the continental slope — where the North American continent ends and drops into the Atlantic Ocean basin — at risk for these landslides, ten Brink said. Another possible source for East Coast tsunamis is the Azores-Gibraltar Transform Fault, off the coast of Portugal. One massive earthquake along this fault in 1755 destroyed most of Lisbon and created a tsunami recorded as far away as Brazil. It was barely noticed on the East Coast, however, ten Brink said. His group has created computer models that suggest underwater mountains west of Portugal helped reduce the impact of this tsunami by slowing the waves and disrupting their movement— and they could do the same thing in the future. The nearby Canary Islands, off the coast of Morocco, also present a possible hazard. One large volcano on the island of La Palma, called Cumbre Vieja, could erupt, collapse and create a large tsunami capable of reaching the East Coast. A 2001 study suggested this series of events could send a 70-foot (21 m) wave crashing into the East Coast. But ten Brink said that study hasn’t held up to subsequent review, and that the wave would be unlikely to exceed several feet in height by the time it reached North America. “I don’t see it as a credible threat,” he said. The last possible tsunami source is a slow-moving fault north of Cuba, which has caused earthquakes in the past and possibly could create a tsunami that affected Florida and the Gulf Coast. Due to the current political situation, neither Cuban nor American researchers can conduct research in the area, he said. –MNN

Researchers find undersea gas leaks off Israel’s coast

ISRAEL – A new geophysical study, the first of its kind in Israel, has uncovered a system of active gas springs in the Haifa Bay seabed, at relatively shallow depths, only a few dozen meters below the surface. A study, published in the journal Continental Shelf Research, describes the entire system, from its sources under the sea floor through the natural springs emerging from the seabed. “This is a natural laboratory for researching gas emissions from the sea floor – natural springs and less natural ones. We are only beginning to understand their contribution to climate and ecological change,” said Dr. Uri Schattner of the Leon H. Charney School of Marine Sciences at the University of Haifa, who led the research. The first evidence of gas springs emerged from examining a map of the sea floor off Israel’s northern coast. A joint effort between the University of Haifa and the Israel Oceanographic and Limnological Research Institute revealed no less than 700 spots in the seabed that looked like possible gas springs. The researchers’ suspicions intensified when seismic data identified pockets of gas beneath the seabed. Based on this evidence, researchers went out to sea four times to collect more data from the seabed and from under the sea floor. “Geophysical information enables us to research beneath the sea floor and map out the entire system, from the gas sources to their penetration of the sea waters,” said Dr. Schattner. However, what they found exceeded all expectations. A gas deposit of 72 square kilometers was found on the continental shelf, at depths of between 37 meters to 112 meters. While many of the gases remain in the reserve, some still manage to escape into the sea. “We don’t know yet what kind of gas we’re talking about, but its role in undermining the stability of the seabed is clear,” said Dr. Michael Lazar, a member of the research team. “This means that any discussion of marine infrastructure development must seriously relate to this shallow gas stratum.” Israel’s Energy and Water Ministry is expending a great deal of effort on formulating National Master Plan 37H, which, among other things, deals with the transportation of gas produced from deep-sea drilling to pressure-reducing facilities. These will be located on the continental shelf, in the sea, from where the gas will be transported to the coast. “Now we are beginning to understand that there is no substitute for thoroughly researching the stability of the sea floor to prevent an infrastructure failure, since any leak could cause an ecological disaster,” said Dr. Schattner. During the coming months, the researchers will be making another expedition to the springs, this time with a team of biologists and geologists. This unique combination of experts from the Leon H. Charney School of Marine Sciences will be able to provide a better understanding of the type of gas involved and its influence on marine life near the sea floor. “Every research trip challenges and fascinates us anew,” said Dr. Schattner. “This time we’ll be going out with a few vessels, each of which is dedicated to different types of surveying and sampling.” –Physics

70% of Venice slips underwater in the worst flooding in 140 years

VENICE – Tourists attached plastic bags to their legs or stripped off to take a dip in St Mark’s Square in Venice on Sunday as rising sea waters surged through the lagoon city. High water measuring 1.49 metres (5ft) above the normal level of the Adriatic sea came with bad weather that swept Italy at the weekend, causing floods in historic cities including Vicenza as well in the region of Tuscany 250 miles further south. Venice’s high water, or “acqua alta,” said to be the sixth highest since 1872, flooded 70% of the city and was high enough to make raised wooden platforms for pedestrians float away. The record high water in Venice – 1.94 meters in 1966 – prompted many residents to abandon the city for new lives on the mainland. Venetians bombarded Facebook with moans about the city’s weather forecasters, who had predicted just 1.2 metres of water on Saturday, before correcting their forecast at dawn on Sunday. “How come the people from the council who put out the wooden platforms were predicting 150cm?” asked Matelda Bottoni, who manages a jewelry design shop off St Mark’s Square, which floods when water reaches 105cm. “Many residents and shopkeepers had gone to the mountains for the day and did not have time to rush back.” Bottoni is so used to floods she has installed waterproof furniture and an angled floor. “I cannot keep the water out, but at least I can make sure it goes straight back out when it recedes,” she said. Matteo Secchi, a hotelier and head of a protest group, who grew up in ground floor flat in Venice and recalls splashing into water on getting out of bed, said his hotel was only safe up to 140cm. “This morning the lagoon came right into the hotel entrance, and this is not clean water – you need to mop with disinfectant twice after it goes down,” he said. “The British tourists don’t complain but the Americans can’t understand how it’s possible.” Secchi complained that a running event around the city had not been cancelled on Sunday. “As Venetians were trying to fix their homes and shops, people were running down the flooded streets splashing everyone with water,” he said. Alessandro Maggioni, the city’s assessor for public works, defended the Venice weather centre, describing the high water as “exceptional and unpredictable.” The Moses flood barrier system being built to protect the lagoon, due for completion in 2015, would have kept the city dry, he said. “Meanwhile, there is no rise in the incidence of high waters,” he said. Bottoni disagreed. “My shop now has some form of flooding 100 days a year, up from 30-40 days when I moved in just 10 years ago.” But she does not plan to leave. “I was born and raised here and will stay here for the satisfaction of being in Venice.” –Guardian