AP Photo/Hallstatt.net, Werner Krauss1 of 10
Floodwater rushes down a street in the village of Hallstatt, Austria, Wednesday, June 19. A flash flood unleashed by a major thunderstorm has inundated the village, which has special status as a UNESCO World Heritage Site by the United Nations because of its unique beauty. Wednesday's storm turned the placid village creek into a raging torrent that flooded the village square, tearing up cobble stones in its wake. Houses and a hotel are partially under water.
AP Photo/Nelson Antoine2 of 10Protestors burn a Sao Paulo state flag in front of City Hall, in Sao Paulo, Brazil, Tuesday, June 18. Some of the biggest demonstrations since the end of Brazil's 1964-85 dictatorship have broken out across the country, uniting multitudes frustrated by poor transportation, health services, education and security despite a heavy tax burden.
AstroKarenN/Twitter3 of 10
AP Photo/Manish Swarup4 of 10Indian people use a boat to cross a Tibetan refugee market along the banks of the river Yamuna, in New Delhi, India, Wednesday, June 19. With heavy rainfall in northern India water has flooded the banks of the Yamuna. At least 102 people died and 63,000 people remain stranded in the northern Indian state of Uttarakhand following torrential monsoon rains, landslides and cloud bursts.
Interior/Twitter5 of 10
The US Department of Interior tweeted this photo of Grand Staircase-Escalante National Monument on June 18 and wrote, "The #Moon rising over the Grand Staircase-Escalante National Monument in #Utah. @BLMNational pic.twitter.com/0fZAMwHJ4Z"
AP Photo /Ilnar Salakhiev6 of 10Zita, a liger - half-lioness, half-tiger - walks with her month-old liliger cubs in the Novosibirsk Zoo in Russia on Tuesday, June 18, 2013.
Interior/Twitter7 of 10
The US Department of Interior tweeted this photo of kayakers in Kenai Fjords National Park on June 18 and wrote, "June is the perfect time to go #kayaking @KenaiFjordsNPS. Where is your favorite place to kayak? #Alaska pic.twitter.com/w25icfXCS0"
AP Photo/Alexander F. Yuan8 of 10Commuters ride on a subway train at Yonggwang station, or "glory station," in Pyongyang, North Korea, Tuesday, June 18. Foreign visitors are usually allowed to take only one stop, from Puhung station to Yonggwang station, on Pyongyang's north-south Chollima subway line.
Cmdr_Hadfield/Twitter9 of 10
NASA Earth Observatory10 of 10Next: Today's 10 Must-See Photos: 6-18-2013
On most days, relentless rivers of clouds wash over Alaska, obscuring most of the state's 6,640 miles of coastline and 586,000 square miles of land. The south coast of Alaska even has the dubious distinction of being the cloudiest region of the United States. That was certainly not the case on June 17, 2013, the date that the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite acquired this rare, nearly cloud-free view of the state. The absence of clouds exposed a striking tapestry of water, ice, land, forests, and even wildfires. NASA released the image on June 19, 2013.
Articles on this Page
- 06/18/13--09:33: _Tornado Spotted Nea...
- 06/19/13--01:19: _Tropical Depression...
- 06/19/13--01:24: _Monsoon Floods Kill...
- 06/19/13--01:30: _Baked Alaska: Unusu...
- 06/19/13--01:38: _Huge 'Dead Zone' Pr...
- 06/19/13--01:45: _Could Air Pollution...
- 06/19/13--02:00: _Ancient 'Lost' City...
- 06/19/13--03:44: _Today's 10 Must-See...
- 06/19/13--04:30: _Floods Close Lourde...
- 06/19/13--06:18: _Mystery on Venus: '...
- 06/19/13--07:08: _Daredevil to Walk H...
- 06/20/13--01:13: _India Floods Strand...
- 06/20/13--01:20: _Tropical Storm Barr...
- 06/20/13--01:27: _Haze Engulfs Singap...
- 06/20/13--01:33: _Homes Evacuated as ...
- 06/20/13--01:42: _Obama Commits to To...
- 06/20/13--01:49: _Is the African Cont...
- 06/20/13--02:01: _Severe Weather Take...
- 06/20/13--03:20: _Today's 10 Must-See...
- 06/20/13--03:50: _Photos: Floodwaters...
- 06/18/13--09:33: Tornado Spotted Near Denver Airport Terminal
- 06/19/13--01:19: Tropical Depression Churns Toward Mexican Coast
- 06/19/13--01:24: Monsoon Floods Kill 102 in India, Strands Pilgrims
- 06/19/13--01:30: Baked Alaska: Unusual Heat Wave Hits 49th State
- 06/19/13--01:38: Huge 'Dead Zone' Predicted in Gulf of Mexico
- World's 10 Most Polluted Places
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- 06/19/13--01:45: Could Air Pollution Be Linked to Autism?
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- 06/19/13--02:00: Ancient 'Lost' City Discovered in Cambodia
- 06/19/13--03:44: Today's 10 Must-See Photos: 6-19-2013
- 06/19/13--04:30: Floods Close Lourdes Pilgrimage Site in Pyrenees
- 06/19/13--06:18: Mystery on Venus: 'Super-Hurricane' Force Winds Get Stronger
- Photos: Most Powerful Storms of the Solar System
- Amazing Venus Photos by ESA's Venus Express
- Planet Venus: Quiz Yourself on Venus Facts
- 06/19/13--07:08: Daredevil to Walk High Wire Over Grand Canyon on Live TV
- 06/20/13--01:13: India Floods Strand Thousands; More Than 100 Dead
- 06/20/13--01:20: Tropical Storm Barry Makes Landfall in Mexico
- 06/20/13--01:27: Haze Engulfs Singapore, Malaysia Schools Shut
- 06/20/13--01:33: Homes Evacuated as Wildfire Flares Near Denver
- 06/20/13--01:42: Obama Commits to Tough Push on Global Warming
- 06/20/13--01:49: Is the African Continent Ripping Apart?
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- 06/20/13--02:01: Severe Weather Takes Aim at Upper Midwest
- 06/20/13--03:20: Today's 10 Must-See Photos: 6-20-2013
AP Photo/Natacha Pisarenko1 of 10Brazil's Hulk, left, performs a bicycle kick as Mexico's Jorge Torres, right, looks on during the soccer Confederations Cup group A match between Brazil and Mexico at Castelao stadium in Fortaleza, Brazil, Wednesday, June 19, 2013.
AP Photo2 of 10
A submerged idol of Hindu Lord Shiva stands in the flooded River Ganges in Rishikesh, in the northern Indian state of Uttarakhand, India, June 18, 2013. Monsoon torrential rains have cause havoc in northern India leading to flash floods, cloudbursts and landslides as the death toll continues to climb and more than 1,000 pilgrims bound for Himalayan shrines remain stranded.
AP Photo/Renata Britto3 of 10
Christ the Redeemer statue stands above Rio de Janeiro, Brazil, Wednesday, June 19, 2013. Scattered street demonstrations popped up around Brazil Wednesday as protesters continued their collective cry against the low-quality public services they receive in exchange for high taxes and rising prices.
AP Photo/Adel Hana4 of 10Palestinian youths march during a military style exercise run by Hamas during a scouting summer camp next to the border between Egypt and Rafah, southern Gaza Strip, Wednesday, June 19, 2013.
AP Photo/Bob Edme5 of 10A vehicle tire floats past the flooded grotto of Lourdes, in Lourdes, southwestern France, Wednesday, June 19, 2013. Heavy floods have forced the closure of the Catholic pilgrimage site in Lourdes and the evacuation of pilgrims from nearby hotels. Floodwaters swirled Wednesday in the grotto where nearly 6 million believers from around the world, many gravely ill, come every year seeking miracles and healing.
AP Photo/Harry How, Pool6 of 10
Chicago Blackhawks right wing Patrick Kane, left, shoots as Boston Bruins goalie Tuukka Rask (40), of Finland, leaps in vain as Kane's shot scored during the second period in Game 4 of the NHL hockey Stanley Cup Finals Wednesday, June 19, 2013, in Boston. Blackhawks center Jonathan Toews (19), and Bruins defensemen Andrew Ference (21) watch. Chicago won 6-5 to even the series 2-2.
Interior/Twitter7 of 10
The US Department of Interior tweeted this photo of a fox at Yellowstone National Park on June 19 and wrote, "You never know what you'll spot in America's National Parks. Like this red fox leaping for its prey @YellowstoneNPS pic.twitter.com/AqmrzCuXgi"
AstroKarenN/Twitter8 of 10
Astronaut Karen L Nyberg tweeted this photo of the El Salvador, Nicaragua and Honduras from the International Space Station on June 19. She wrote, "El Salvador, Honduras, Nicaragua. pic.twitter.com/T8hJ1CdTuS"
Interior/Twitter9 of 10
The US Department of Interior tweeted this photo of Alaska on June 19 and wrote, "One of the best things about visiting @BLMNational lands in #Alaska. The chance to get away from it all. pic.twitter.com/J1s2id9YJP"
- 06/20/13--03:50: Photos: Floodwaters Deluge India
Tsering Topgyal/AP Photo1 of 10
A joint army and air force operation has so far evacuated nearly 13,000 people stranded in the upper reaches of the state of Uttarakhand, India where days of rain had earlier washed out houses, temples, hotels and vehicles leading to deaths of over a hundred people.
At left, houses along the banks of the Yamuna River that lie submerged in flood water in New Delhi, India, Thursday, June 20, 2013.
PRAKASH SINGH/AFP/Getty Images2 of 10Indian workers from the Municipal Corporation of Delhi (MCD) clear a clogged drain on a water logged road as the waters of the Yamuna River rise in New Delhi on June 20, 2013. Military helicopters dropped emergency supplies June 19 to thousands of people stranded by flash floods that tore through towns and temples in northern India and neighbouring Nepal.
AP Photo3 of 10An Indian man consoles his relatives after they were evacuated by helicopter from upper reaches of Uttrakhund, in Dehradun, India, Thursday, June 20, 2013.
Tsering Topgyal/AP Photo4 of 10People gather to look at submerged buses and trucks in the rising Yamuna River as they stand on a flyover in New Delhi, India, Wednesday, June 19, 2013. India's prime minister said Wednesday that the death toll from flooding this week in the northern state of Uttrakhand had surpassed 100 and could rise substantially. The flooding has affected several states and the capital New Delhi where nearly 2,000 people have been evacuated to government-run camps on higher ground. Authorities there said the situation would ease as the level of the Yamuna River was expected to start receding Thursday afternoon.
Manish Swarup/AP Photo5 of 10Indian people stand near trucks partly submerged in floodwaters along the banks of the Yamuna River, in New Delhi, India, Wednesday, June 19, 2013. India's prime minister said Wednesday that the death toll from flooding this week in the northern state of Uttrakhand had surpassed 100 and could rise substantially. The flooding has affected several states and the capital, New Delhi, where nearly 2,000 people have been evacuated to government-run camps on higher ground. Authorities there said the situation would ease as the level of the Yamuna River was expected to start receding Thursday afternoon.Indian people stand near trucks partly submerged in floodwaters along the banks of the Yamuna River, in New Delhi, India, Wednesday, June 19, 2013. India's prime minister said Wednesday that the death toll from flooding this week in the northern state of Uttrakhand had surpassed 100 and could rise substantially. The flooding has affected several states and the capital, New Delhi, where nearly 2,000 people have been evacuated to government-run camps on higher ground. Authorities there said the situation would ease as the level of the Yamuna River was expected to start receding Thursday afternoon.
adgpi/twitter6 of 10
TellyNewsIndia/twitter7 of 10
Telly News India tweeted this photo of flooding in India on June 17 and wrote, "Sad 2 Hear ShivMurti Being Swept Away By Flood Water In Rishikesh.After 2010,Now In 2013 Also.#FloodFury #Uttarakhand pic.twitter.com/GSWRPX1DGN"
Tsering Topgyal/AP Photo8 of 10
Commuters travel on a flooded road after a rise in the water levels of the Yamuna River in New Delhi, India, Thursday, June 20, 2013. The latest rains have affected several states and the capital, New Delhi, where nearly 2,000 people were evacuated to government-run camps on higher ground.
AP Photo9 of 10
In this Wednesday, June 19, 2013, photo, Indian army doctors treat a flood affected elderly person inside a makeshift tent, in Chamoli, in the Indian northern state of Uttrakhand.
Tsering Topgyal/AP Photo10 of 10Next: 50 Must-See Weather PhotosChildren splash around in a flooded area along the banks of the Yamuna River in New Delhi, India, Thursday, June 20, 2013.
Eric Fisher tweeted this photo on June 18 and wrote, "Amazing photo of #tornado passing right next to Denver International Airport! -> pic.twitter.com/Q4PXe2A926" (EricFisherTWC/Twitter)
DENVER (AP) - Radar indicated a tornado briefly touched down Tuesday over the east runways of Denver International Airport, where thousands of people took shelter in bathrooms, stairwells and other safe spots until the dangerous weather passed, officials said.
There was no significant damage, airport spokeswoman Laura Coale said. Some flights headed to Denver were diverted elsewhere during a tornado warning that lasted about 30 minutes, she said.
A 97 mph wind gust was measured at the airport before communication with instruments there was briefly knocked out, said National Weather Service meteorologist Kyle Fredin.
Chris Polk, a construction foreman, was working on a renovation project just outside the airport's main concourse when he got the tornado warning at 2:15 p.m., looked up and saw a funnel cloud. He and his crew ran inside and took shelter with some 100 people, including luggage-toting passengers, inside a basement break room.
"It got pretty crazy around here," Polk said. Asked whether he was nervous when he spotted the funnel cloud, he shrugged. "No, I'm from Missouri," he said.
Everyone inside the break room was calm, Polk added.
It wasn't clear how many people were at the airport when a public announcement went out about the tornado warning, but the airport averages about 145,000 passengers over the course of a day, Coale said.
Television coverage showed the airport's normally busy terminal was empty during the warning. Access to a bridge to concourse A was blocked, since the bridge is surrounded by large glass windows.
As the storm passed, police briefly blocked traffic from Interstate 70 to Pena Boulevard, which leads to the airport.
Scott Morlan said he had dropped his daughter off at airport and was heading out when he saw an ominous cloud.
"It was just turning. You knew it was thinking about coming down," he said.
He watched the tip of funnel cloud touch the ground and cross Pena Boulevard before lifting into the sky.
On Monday, a tornado touched down briefly in La Junta on Colorado's southeastern plains. Power poles were knocked down in an industrial park, but no injuries were reported, said weather service spokeswoman Nezette Rydell said.
Heavy rain fell there, as well as in Lamar, where some streets flooded. The area is among those hardest hit by the drought in the West.
La Junta Fire Chief Aaron Eveatt said high winds downed power poles, temporarily closing U.S. 50. A gas station canopy was toppled and a co-op storage tower also suffered damage.
Mark Sarlo, the manager of the Phillips 66 station, said he was driving to the station just before 6 p.m. Monday when the sky turned dark brown and yellow, the rain began to pound, and wind shook his truck. He stopped and got on the floor as debris hit.
As soon as the storm passed, Sarlo said residents in the town of 7,000 were out with chain saws removing downed poles and trees blocking streets. They also cut up his canopy and hauled it in chunks to an empty lot so he could resume business. One family brought bottled water and pizzas to feed the crews.
"It's just amazing," he said of the response of his hometown.
PHOTOS ON SKYE: Stunning Photos from the 2013 Tornado Season
MIAMI (AP) - Forecasters say a tropical depression crossing Mexico's Bay of Campeche is getting better organized and is expected to become a tropical storm before making landfall along Mexico's Gulf Coast.
The National Hurricane Center in Miami said the Atlantic season's second tropical depression is drenching areas in its path with up to 10 inches of rain in some places, raising the threat of flash floods.
The depression formed Monday off Belize and was about 115 miles east of Veracruz, Mexico, on Wednesday. It is expected to strengthen before making landfall Thursday morning in Veracruz.
The storm has maximum sustained winds of 35 mph. A tropical storm warning is in effect from Punta El Lagarto to Barra de Nautla.
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A view of the Hindu holy town of Kedarnath from a helicopter after a flood, in the northern Indian state of Uttarakhand, India, Tuesday, June 18, 2013. (AP Photo)
LUCKNOW, India (AP) - India's prime minister said Wednesday that the death toll from flooding this week in the northern state of Uttrakhand had surpassed 100 and could rise substantially.
Prime Minister Manmohan Singh spoke on his return from an aerial survey of the area, pegging the death toll at 102.
"It is feared that the loss of life could be much higher," he said.
Uttrakhand's top elected official, State Chief Minister Vijay Bahuguna later told the New Delhi Television news channel that hundreds of people have lost their lives but that the exact number would be known only after a survey of the area.
A joint army and air force operation evacuated nearly 12,000 Hindu pilgrims stranded in a mountainous area by torrential monsoon rains and landslides, but nearly 63,000 people remained cut off, a senior official said Wednesday.
Home Minister Sushilkumar Shinde earlier said the flooding in Uttrakhand washed away roads and nearly two dozen bridges and demolished 365 houses and partially damaged 275 others.
A three-story apartment building toppled into a river on Sunday and was carried away by the flood waters, said Amit Chandola, a Uttrakhand government spokesman, adding that a helicopter on its landing pad also was swept away. The government also said 40 small hotels on the banks of the Mandakini river in the Gaurikund area were destroyed by the swift-moving current.
Describing the situation as grim, Bahuguna said his administration was not equipped to tackle such a massive disaster, and asked for federal assistance. The region is 400 kilometers (250 miles) southwest of Lucknow, the capital of Uttar Pradesh state.
An additional 17 people have died since Sunday when their homes collapsed in Uttar Pradesh state, which borders Uttrakhand, said R.L. Vishwakarma, a state police officer.
The flooding has affected several states and the capital, New Delhi, where nearly 2,000 people have been evacuated to government-run camps on higher ground. Authorities there said the situation would ease as the level of the Yamuna River was expected to start receding Thursday afternoon.
Flooding is an annual occurrence in India, which depends on monsoon rains to sustain agriculture. But the heavy downpours also cause the loss of lives and property.
Most of those stranded in Uttrakhand are Hindu pilgrims to four revered shrines in the region. Bahuguna said the Kedarnath temple - one of the holiest Hindu temples dedicated to Lord Shiva, located atop the Garhwal Himalayan range - had escaped major damage, but up to 10 feet (four meters) of debris covered the area around it.
"We are fully engaged in rescuing people who have been stranded in the higher reaches," Bahuguna told reporters earlier. Nearly 600 people were evacuated by air force helicopters and the rest by the army using land routes.
With the sky over Uttrakhand clearing up Wednesday, the helicopter operation concentrated on the worst-hit Kedarnath temple area, which received 380 millimeters (14 inches) of rain in the past week, nearly five times the average for that time period,, said R.P.N. Singh, junior home minister.
Air force spokeswoman Priya Joshi said 22 helicopters have dropped food packets and other relief supplies in addition to ferrying stranded tourists. More than 5,000 soldiers helped bring thousands of homeless people to relief camps and provided them with food and medical supplies.
RELATED ON SKYE: Incredible Natural-Disaster Photos from Space
In this photo taken Monday, June 17, 2013, people swim and sunbathe at Goose Lake in Anchorage, Alaska. (AP Photo/Rachel D'Oro)
ANCHORAGE, Alaska (AP) - A heat wave hitting Alaska may not rival the blazing heat of Phoenix or Las Vegas, but to residents of the 49th state, the days of hot weather feel like a stifling oven - or a tropical paradise.
With temperatures topping 80 degrees in Anchorage, and higher in other parts of the state, people have been sweltering in a place where few homes have air conditioning.
RELATED ON SKYE: 15 Stunning Photos of Alaska
They're sunbathing and swimming at local lakes, hosing down their dogs and cleaning out supplies of fans in at least one local hardware store. Mid-June normally brings high temperatures in the 60s in Anchorage, and just a month ago, it was still snowing.
The weather feels like anywhere but Alaska to 18-year-old Jordan Rollison, who was sunbathing with three friends and several hundred others lolling at the beach of Anchorage's Goose Lake.
"I love it, I love it," Rollison said. "I've never seen a summer like this, ever."
State health officials even took the unusual step of posting a Facebook message reminding people to slather on the sunscreen.
Some people aren't so thrilled, complaining that it's just too hot.
"It's almost unbearable to me," said Lorraine Roehl, who has lived in Anchorage for two years after moving here from the community of Sand Point in Alaska's Aleutian Islands. "I don't like being hot. I'm used to cool ocean breeze."
On Tuesday, the official afternoon high in Anchorage was 81 degrees, breaking the city's record of 80 set in 1926 for that date.
Other smaller communities throughout a wide swath of the state are seeing even higher temperatures.
All-time highs were recorded elsewhere, including 96 degrees on Monday 80 miles to the north in the small community of Talkeetna, purported to be the inspiration for the town in the TV series, "Northern Exposure" and the last stop for climbers heading to Mount McKinley, North America's tallest mountain. One unofficial reading taken at a lodge near Talkeetna even measured 98 degrees, which would tie the highest undisputed temperature recorded in Alaska.
That record was set in 1969, according to Jeff Masters, meteorology director of the online forecasting service Weather Underground.
"This is the hottest heat wave in Alaska since '69," he said. "You're way, way from normal."
It's also been really hot for a while. The city had six days over 70 degrees, then hit a high of 68 last Thursday, followed by five more days of 70 degrees and up.
The city's record of consecutive days with temperatures of 70 or above was 13 days recorded in 1953, said Eddie Zingone, a meteorologist with the National Weather Service who has lived in Anchorage for 17 years.
The heat wave also comes after a few cooler summers - the last time it officially hit the 80 mark in Anchorage was 2009. Plus, Tuesday marked exactly one month that the city's last snow of the season fell, Zingone said.
"Within a month you have that big of a change, it definitely seems very, very hot," he said. "It was a very quick warm-up."
With the heat comes an invasion of mosquitoes many are calling the worst they've ever seen. At the True Value Hardware store, people have grabbed up five times the usual amount of mosquito warfare supplies, said store owner Tim Craig. The store shelves also are bare of fans, which is unusual, he said.
"Those are two hot items, so to speak," he said.
Greg Wilkinson, a spokesman with the Alaska Department of Health and Social Services, said it's gotten up to 84 degrees at his home in the Anchorage suburb of Eagle River, where a tall glass front lets the sunlight filter through.
"And that's with all the windows open and a fan going," he said. "We're just not used to it. Our homes aren't built for it."
Love or hate the unusual heat, it'll all be over soon.
Weather forecasters say a high pressure system that has locked the region in clear skies and baking temperatures has shifted and Wednesday should be the start of a cooling trend, although slightly lower temperatures in the 70s are still expected to loiter into the weekend.
RELATED ON SKYE: 15 Stunning Photos of Alaska
Areas with low levels of oxygen are referred to as dead zones. Red areas correspond to less oxygen. (Credit: NOAA)
A very large dead zone, an area of water with no or very little oxygen, is expected to form in the Gulf of Mexico this year - a trend in recent years, according to the National Oceanic and Atmospheric Administration (NOAA).
Computer models put together by scientists predict that the zone will cover an area between 7,286 and 8,561 square miles (18,871 to 22,173 square kilometers) this summer, the typical time for such zones to form. The large end of the estimate is roughly the size of the state of New Jersey, and would be the largest dead zone ever recorded. The biggest one recorded to date, in 2002, reached 8,481 square miles (21,966 square km).
Meanwhile, models predict the dead zone in the Chesapeake Bay will be smaller than usual.
The makings of a dead zone begin with nutrient pollution, primarily fertilizers and agricultural runoff. Once these excess nutrients reach the ocean, they fuel algae blooms. The algae then die and decompose in a process that consumes oxygen and creates lifeless areas where fish and other aquatic creatures can't survive. This zone can have serious impacts on commercial and recreational fisheries on the Gulf Coast.
Conditions are ripe for a large dead zone this summer, thanks to heavy rains throughout much of the Midwest this spring that have caused water nutrient runoff (for example, from farm fertilizer) with it, according to a NOAA statement.
Last year's dead zone was smaller than average due, in large part, to the drought that gripped much of the country. It reached a maximum size of about 2,889 square miles (7,483 square km), an area slightly larger than the state of Delaware. Since 1995, the average Gulf dead zone has been 5,960 square miles (15,436 square km), an area a little larger than the size of Connecticut.
The official size of the Gulf hypoxic, or dead zone, will be released in August, according to the statement.
RELATED ON SKYE: Could a Trip to Your Favorite Beach Make You Sick?
Residential buildings shrouded in haze in Singapore on June 17, 2013. (ROSLAN RAHMAN/AFP/Getty Images)
Pregnant women who are exposed to high levels of air pollution may be more likely to give birth to children with autism, according to a new study.
The researchers found that the pregnant women in the study who lived in the most-polluted areas were up to two times more likely to have a child with an autism spectrum disorder (ASD), compared with those who lived in the least-polluted areas.
The air pollutants linked to autism included diesel fuel, lead, manganese and mercury. For most pollutants that the researchers studied, associations with autism were stronger in boys than in girls.
The results add to evidence found in previous studies suggesting that air pollution might be a risk factor for autism.
It is not clear how heavy metals or other chemicals found in air pollution may affect a developing fetus, but studies have shown traffic-related pollutants, such as diesel, can induce inflammation of the brain in animals, the researchers said.
"Our results suggest that new studies should begin the process of measuring metals and other pollutants in the blood of pregnant women or newborn children to provide stronger evidence that specific pollutants increase risk of autism," said study researcher Marc Weisskopf, associate professor of environmental and occupational epidemiology at Harvard School of Public Health.
In the study, the researchers looked at 325 women who had a child with autism and 22,000 women who had a child without autism. Using air-pollution data from the U.S. Environmental Protection Agency, the researchers estimated levels of pollutants at the time and place of each child's birth.
The results showed that women living in areas with the highest levels of diesel or mercury in the air were twice as likely to have a child with ASD, compared with those living in the areas with the lowest levels.
Women who were exposed to other types of air pollution - such as lead, manganese and methylene chloride - were about 50 percent more likely to have a child with ASD than women who lived in the areas with the lowest concentrations of these pollutants.
The results held after adjusting for other possible ASD risk factors, such as parents' income, education and smoking during pregnancy. However, the findings show a link - not a cause-and-effect relationship - between autism and pollution, the researchers said. More work is needed to confirm the results.
There were 279 boys and 46 girls with ASD in the study. While the link with pollution seemed stronger for boys compared with girls, the researchers noted there were few girls with autism in the study, and said the finding should be examined further.
Another explanation for the gender difference in the results is that boys may have a generally greater vulnerability to ASD, the researchers said. The toxic effects of air pollutant may impact boys' development more easily or profoundly, resulting in autism, they said.
The study was published today (June 18) in the journal Environmental Health Perspectives.
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Cambodia's famed Angkor Wat temples complex stands in Siem Reap province, some 143 miles northwest Phnom Penh, Cambodia. (AP Photo/Heng Sinith)
SYDNEY (AP) - Airborne laser technology has uncovered a network of roadways and canals, illustrating a bustling ancient city linking Cambodia's famed Angkor Wat temple complex.
The discovery was announced late Monday in a peer-reviewed paper released early by the journal Proceedings of the National Academy of Sciences. The laser scanning revealed a previously undocumented formally planned urban landscape integrating the 1,200-year-old temples.
The Angkor temple complex, Cambodia's top tourist destination and one of Asia's most famous landmarks, was constructed in the 12th century during the mighty Khmer empire. Angkor Wat is a point of deep pride for Cambodians, appearing on the national flag, and was named a UNESCO World Heritage Site.
Archaeologists had long suspected that the city of Mahendraparvata lay hidden beneath a canopy of dense vegetation atop Phnom Kulen mountain in Siem Reap province. But the airborne lasers produced the first detailed map of a vast cityscape, including highways and previously undiscovered temples.
"No one had ever mapped the city in any kind of detail before, and so it was a real revelation to see the city revealed in such clarity," University of Sydney archaeologist Damian Evans, the study's lead author, said by phone from Cambodia. "It's really remarkable to see these traces of human activity still inscribed into the forest floor many, many centuries after the city ceased to function and was overgrown."
The laser technology, known as lidar, works by firing laser pulses from an aircraft to the ground and measuring the distance to create a detailed, three-dimensional map of the area. It's a useful tool for archaeologists because the lasers can penetrate thick vegetation and cover swaths of ground far faster than they could be analyzed on foot. Lidar has been used to explore other archaeological sites, such as Stonehenge.
In April 2012, researchers loaded the equipment onto a helicopter, which spent days crisscrossing the dense forests from 800 meters (2,600 feet) above the ground. A team of Australian and French archaeologists then confirmed the findings with an on-foot expedition through the jungle.
Archaeologists had already spent years doing ground research to map a 9-square-kilometer (3.5-square-mile) section of the city's downtown area. But the lidar revealed the downtown was much more expansive - at least 35 square kilometers (14 square miles) - and more heavily populated than once believed.
"The real revelation is to find that the downtown area is densely inhabited, formally-planned and bigger than previously thought," Evans said. "To see the extent of things we missed before has completely changed our understanding of how these cities were structured."
Researchers don't yet know why the civilization at Mahendraparvata collapsed. But Evans said one theory is that possible problems with the city's water management system may have driven people out.
The next step for researchers involves excavating the site, which Evans hopes will reveal clues about how many people once lived there.
PHOTOS ON SKYE: Breathtaking Images of Earth from Space
The sanctuary of Lourdes flooded, in Lourdes, southwestern France, Tuesday, June 18, 2013. (AP Photo/Bob Edme)
LOURDES, France (AP) - Heavy floods in southwest France have forced the closure of the Catholic pilgrimage site in Lourdes and the evacuation of pilgrims from nearby hotels.
Muddy floodwaters swirled Wednesday in the grotto where nearly 6 million believers from around the world, many gravely ill, come every year seeking miracles and healing. It has been a major pilgrimage site since a French girl's vision of the Virgin Mary there in 1858.
Lourdes Mayor Jean-Pierre Artiganave said on BFM television that the pilgrimage complex in the foothills of the Pyrenees will not reopen until safety can be assured. Diocese spokesman Mathias Terrier said that wasn't likely before the end of the week.
Rescue services evacuated hundreds of people from nearby hotels. Authorities were particularly concerned with bringing weak and sick pilgrims to safety.
Heavy rains around the region inundated town centers and swelled the Gave de Pau river, forcing road closures.
"We need more reinforcements in the area to face these floods, which are really exceptional," Interior Minister Manuel Valls said while visiting Lourdes on Wednesday. He said days of sustained rains and sudden snowmelt made the flooding worse, and left some villages isolated.
The website for the pilgrimage complex, which includes several buildings and a sanctuary nestled beneath a rocky hillside, carried a dramatic rundown of the rising waters.
Throughout Tuesday, masses were gradually cancelled. One by one, entrances to the sanctuary were cordoned off. The live video feed of the grotto went down. Then the electricity was cut off, and then phones.
"A vision of the apocalypse in the Sainte Bernadette Church, where the big movable partition is threatening to fall. The water has risen above the stairs of the choir," read one announcement.
Terrier said waters reached about 5 feet in the grotto. A group of 3,000 children scheduled to come for the day Wednesday were told to stay away. Volunteers offered to help clean up the site when the waters recede.
PHOTOS ON SKYE: 50 Must-See Weather Photos
Wednesday, June 19, 2013
This false-color image by the Venus Monitoring Camera (VMC) on the European Space Agency's Venus Express shows cloud features on the planet. The image was captured from a distance of 19,000 miles on 8 Dec. 8, 2011. (ESA/MPS/DLR/IDA)
The howling, hurricane-force winds of Venus are blowing even faster lately, and scientists aren't sure why.
Average cloud-top wind speeds on Venus rose 33 percent between 2006 and 2012, jumping from 186 mph to 249 mph, observations by Europe's Venus Express orbiter show.
"This is an enormous increase in the already high wind speeds known in the atmosphere," Igor Khatuntsev of the Space Research Institute in Moscow said in a statement. "Such a large variation has never before been observed on Venus, and we do not yet understand why this occurred." [Mysterious Venus: 10 Weird Facts]
Khatuntsev and his team determined wind speeds by studying images captured by Venus Express between 50 degrees north and south latitude. The researchers tracked the movements of tens of thousands of features in the cloud tops some 43 miles (70 kilometers) above the planet's surface.The strange winds of Earth's "sister planet" have long intrigued researchers. Venus has a super-rotating atmosphere that whips around the planet once every four Earth days; Venus itself takes 243 Earth days to complete one rotation. European Space Agency officials described the strong Venusian winds as "super-hurricane-force" phenomena.
Their work has been accepted for publication in the journal Icarus. A Japanese-led team also tracked cloud movements using Venus Express data in a separate but complementary study that will be published in the Journal of Geophysical Research.
"Our analysis of cloud motions at low latitudes in the southern hemisphere showed that over the six years of study the velocity of the winds changed by up 70 km/h over a time scale of 255 Earth days - slightly longer than a year on Venus," lead author Toru Kouyama, of the Information Technology Research Institute in Ibaraki, Japan, said in a statement.
Both new studies also detected regular variations in the atmosphere of Venus that appear to be linked to the rotational period of the planet, the local time of day and the height of the sun above the horizon, researchers said.
And both teams saw surprising and dramatic variations in wind speed, sometimes in as little as 24 hours. Sometimes clouds took 3.9 days to zip all the way around Venus, for example, while on other occasions the journey required 5.3 days.
The reasons for such shifts, as well as the long-term increase in wind speed, remain mysterious, scientists said.
"Although there is clear evidence that the average global wind speeds have increased, further investigations are needed in order to explain what drives the atmospheric circulation patterns that are responsible, and to explain the changes seen in localized areas on shorter timescales," Venus Express project scientist Håkan Svedhem said in a statement.
"The atmospheric super-rotation of Venus is one of the great unexplained mysteries of the solar system," Svedhem added. "These results add more mystery to it, as Venus Express continues to surprise us with its ongoing observations of this dynamic, changing planet."
On Sunday, June 23, tightrope walker Nik Wallenda plans to walk across the Grand Canyon on a 2-inch-thick cable on live TV. The line he'll traverse will be suspended 1,500 feet above the Little Colorado River, and he'll have no safety tether attaching himself to the wire.
"Definitely the first couple steps are the hardest," says Wallenda. "Once I get on that wire I become very peaceful, calm and relaxed."
Wallenda has pulled off some pretty big stunts before. Last year, crossed Niagara Falls on a tightrope.
The event starts at 8 p.m. ET Sunday and will be streamed live by Discovery. You can watch it here.
RELATED ON SKYE: The World's Most Extreme Sports
Updated Thursday, June 20, 11:12 a.m. ET
People gather to watch a bridge submerged in the flooded water of the River Ganges in Rudraprayag, in northern Indian state of Uttarakhand, India, Tuesday, June 18, 2013. (AP Photo)
LUCKNOW, India (AP) - Days after floods killed more than 100 people - possibly many more - rescuers used helicopters and climbed through mountain paths to reach about 4,000 people trapped by landslides in a narrow valley near a Hindu shrine in the northern Himalayas, officials said Thursday.
The helicopters ferried rescue workers and doctors along with equipment, food and medicine to Kedarnath in the state of Uttrakhand, the nearest town to those trapped in the valley, said Air Commodore Rajesh Prasad, who is overseeing the operations.
Amit Chandola, a state spokesman, said authorities so far have been unable to reach eight villages feared washed away by the weekend floods in the worst-hit districts of Rudraprayag and Chamoli.
With the weather improving, army commandos would try to reach the areas on Friday, Chandola said.
He said the official death in Uttrakhand is 105 but added, "We don't know yet what happened to hundreds of people living there." An additional 17 people died in collapsed homes in neighboring Uttar Pradesh state, said R.L. Vishwakarma, a state police officer.
Rakesh Sharma, a state official, said the death toll could be much higher, running into thousands, but the exact number would be known only after a survey of the entire region.
A joint army and air force operation has so far evacuated nearly 14,000 people stranded in the area but nearly 61,000 people remained cut off, officials said.
Chandola said some of the blocked roads were reopened to traffic in the region and nearly 2,000 vehicles moved out of the area carrying stranded tourists.
The flooding washed away roads and nearly two dozen bridges, demolished 365 houses and partially damaged 275 others in Uttrakhand, the state government said. Most of those stranded are Hindu pilgrims who were visiting four revered shrines.
Hundreds of distressed people looking for relatives flocked to Dehradun, the state capital, where flood survivors were taken by plane and helicopter. As those rescued exited the aircraft, those searching for missing people showed them pictures of their loved ones in hopes that someone had seen them.
The lucky ones spoke to their stranded relatives on the phone Wednesday and were waiting for them to be rescued.
State Chief Minister Vijay Bahuguna said the Kedarnath temple - one of the holiest Hindu temples dedicated to Lord Shiva, located atop the Garhwal Himalayan range - had escaped major damage, but up to 10 feet of debris covered the area around it.
The state received 14 inches of rain in the past week, nearly five times the average for that time period, said R.P.N. Singh, India's junior home minister.
Air force spokeswoman Priya Joshi said 30 helicopters and aircraft have dropped food packets and other relief supplies in addition to ferrying stranded tourists. More than 5,000 soldiers helped bring thousands of homeless people to relief camps and provided them with food and medical supplies.
The latest rains have affected several states and the capital, New Delhi, where nearly 2,000 people were evacuated to government-run camps on higher ground. Authorities there said the Yamuna River was expected to start receding Thursday afternoon.
The annual monsoon rains sustain India's agriculture but also cause flooding that routinely claims lives and damages property.
RELATED ON SKYE: Photos: Floodwaters Deluge India
Updated Thursday, June 20, at 11:11 a.m. ET
MIAMI (AP) - Tropical Storm Barry has made landfall in Mexico, threatening deadly flash floods and mudslides as it moves inland.
The U.S. National Hurricane Center in Miami says Barry made landfall Thursday morning. It was forecast to continue moving west over land for the next day or so before weakening and losing its tropical characteristics.
The second tropical storm of the Atlantic season had sustained winds at about 40 mph late Thursday morning. It was moving west at about 5 mph.
A tropical storm warning was in effect from Punta El Lagarto to Tuxpan, in Veracruz state. However, the major concern was heavy rain that could create floods and mudslides, especially in mountain areas.
SEE ON SKYE: Stunning Hurricane Photos from Space
"It's very close to the coast," Hurricane Specialist Lixion Avila told The Associated Press earlier on Thursday, adding a small forward part of the system had begun brushing close to land while most of the vast system was still out over the Gulf of Mexico.
He said the ill-defined tropical storm would be making landfall sometime later Thursday morning, slowly coming ashore over the course of hours.
Between 3 to 5 inches of rain were possible with up to 10 inches in some areas, the hurricane center said.
Avila warned the rains could trigger life-threatening flash floods and mudslides, especially over mountains.
"There is still going to be a lot rain in the hours ahead," he told AP by telephone.
Tropical storm force winds were spreading outward up to 80 miles east from the center of the system.
Early Thursday, blustery winds were already being reported around the Gulf Coast areas closest to the storm's center. Forecasters said tropical storm conditions were already being felt in some areas and that strong winds would continue through Thursday morning.
A tropical storm warning was in effect from Punta El Lagarto to Tuxpan, in Veracruz state.
Veracruz state Civil Protection Secretary Noemi Guzman said 2,000 shelters had been readied in the state with mattresses, blankets, water and canned food. She said the shelters at schools and recreation centers could house up to 306,000 people.
The port of Veracruz was closed to small vessels because of the strong winds, Guzman added.
The storm had formed as a depression off the coast of Belize on Monday and began moving northward, dumping heavy rains on parts of that country and northern Guatemala before entering the Gulf of Mexico off Mexico's Bay of Campeche and strengthening somewhat over warm Gulf waters.
After moving inland Thursday, the storm was expected to weaken throughout the day and then begin breaking apart Friday as it crosses southern Mexico, the hurricane center said.
RELATED ON SKYE: 30 Stunning Photos Revealing the Power of Hurricanes
The sun rises over the Singapore Central Business District, or CBD skyline as the haze or smog envelopes the city on Thursday, June 20, 2013. (AP Photo/Joseph Nair)
SINGAPORE (AP) - Singapore urged people to remain indoors amid unprecedented levels of air pollution Thursday as a smoky haze wrought by forest fires in neighboring Indonesia worsened dramatically. Nearby Malaysia closed 200 schools and banned open burning in some areas.
The Pollutant Standards Index, Singapore's main measure for air pollution, surged to a record reading of 371, breaching the "hazardous" classification that can aggravate respiratory ailments. The previous all-time high before this week was in 1997, when the index reached 226.
The hazardous reading lasted three hours before easing to 253 in the evening, still "very unhealthy."
Smog fueled by raging Indonesian blazes has hit Singapore and Malaysia many times, often in the middle of the year, but the severity of this week's conditions has strained diplomatic ties. Officials in Singapore say Jakarta must do more to halt fires on Sumatra island started by plantation owners and farmers to clear land cheaply.
"This is now the worst haze that Singapore has ever faced," Singapore's Environment Minister Vivian Balakrishnan wrote on his Facebook page. "No country or corporation has the right to pollute the air at the expense of Singaporeans' health and wellbeing."
The haze has shrouded the city-state's skyscrapers in a pall of noxious fumes and posed numerous inconveniences for Singaporeans, some of whom complained of coughs and covered their faces with handkerchiefs while walking outdoors.
Flight controllers at Singapore's Changi Airport were instructed to take precautions because of lower visibility, while McDonald's said it was temporarily halting delivery service to protect its workers' health.
Some hospitals shut windows in wards with elderly patients to keep out the acrid odor of burning. Sports organizers canceled several football and sailing competitions this weekend.
Prime Minister Lee Hsien Loong advised residents to stay indoors as far as possible, adding that "we will get through this together."
Lee told a news conference Thursday that the haze was expected to persist for an unknown number of days because of wind and weather conditions. He announced that a government panel was being formed to protect public health and the city-state's economic resilience.
In neighboring Malaysia, air quality remained relatively unaffected in the country's biggest city, Kuala Lumpur, but a southern state that borders Singapore also recorded "hazardous" pollution in one district, where 200 schools were ordered shut through at least Friday. The Department of Environment banned open burning and made it punishable by up to five years in prison in three states separated from Sumatra by the Malacca Strait.
Indonesian officials have defended their response to the haze, saying the government is educating farmers about alternatives to traditional slash-and-burn agriculture. Some Indonesian officials have also suggested that some fires might be blamed on Singaporean and Malaysian companies involved in Indonesia's plantation industry.
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A military C-130 drops a load of fire retardant on a wildfire near Pine, Colo., on Wednesday, June 19, 2013. (AP Photo/Ed Andrieski)
EVERGREEN, Colo. (AP) - Dozens of homes were evacuated near Denver as a wind-driven wildfire flared, one of many in the western states where hot and windy conditions were making it easy for the wild land blazes to start and spread.
The fire in the foothills about 30 miles southwest of Denver forced evacuations Wednesday affecting more than 100 people, Jefferson County Sheriff Ted Mink said. The Lime Gulch Fire in Pike National Forest was estimated at 500 acres, the U.S. Forest Service said. Mink said no structures appeared to be threatened.
"The good news is, it's a very sparsely populated area as far as houses go," Mink said.
Hundreds of firefighters in Arizona were preparing for more hot, windy weather Thursday, which could help fuel a wildfire in Prescott National Forest that has already scorched nearly 12 square miles. The blaze erupted Tuesday afternoon and led to the evacuation of 460 homes.
To the north, smoke from another fire that broke out Wednesday was visible from Grand Canyon National Park. No structures were immediately threatened.
A blaze in southern New Mexico's Gila National Forest grew to 47 square miles.
But in northern California, hundreds of residents returned home as crews aided by lower temperatures and higher humidity extended their lines around a wildfire near a main route into Yosemite National Park, officials said. Only about 50 homes on two mountain roads remained under evacuation orders, the California Department of Forestry and Fire Protection said. The fire, sparked Sunday by a campfire that wasn't fully put out, led to the evacuation of about 800 homes at its peak.
In southern California, a nearly 6-square-mile fire in the San Bernardino National Forest was 83 percent contained.
The fire near Denver was burning in steep, heavily forested mountain terrain, south of where last year's Lower North Fork Fire damaged and destroyed 23 homes and killed three people. That fire was triggered by a prescribed burn that escaped containment lines.
Mink said the fire might have been sparked by lightning Tuesday, then quickly grew in high winds Wednesday.
Some evacuees said they were ready to leave Wednesday in minutes, having practiced fire evacuations after the Lower North Fork Fire.
Karalyn Pytel was at home vacuuming when her husband called, saying he had received an alert on his cellphone telling the family to leave. She quickly grabbed her 6-year-old daughter's favorite blanket, a laptop computer, a jewelry box and some family heirlooms before fleeing.
"I grabbed a laundry basket and just threw stuff in it. I don't even know what clothes they are," Pytel said as she arrived at an evacuation center.
Firefighters were aided by two U.S. Air Force Reserve C-130s.
C-130s also were used at a 22-square-mile wildfire near Colorado Springs that has destroyed 509 homes and killed two people since it started June 11.
In western Colorado, a wind-driven wildfire near Rangely prompted the evacuation of a youth camp Wednesday. Rio Blanco County Undersheriff Michael Joos said the camp wasn't in immediate danger, but about 40 kids and a half dozen adults were asked to leave due to high winds.
Evacuations also were ordered due to a wildfire in rural Huerfano County in southern Colorado.
Pytel was asked whether the evacuation changed her mind about living in a mountainous area at high risk for wildfires.
"No matter where you go, really, it's always something. It's either a tornado, a hurricane, an earthquake (or) a fire. For us, it's our tornado," Pytel said.
RELATED ON SKYE: Incredible Natural-Disaster Photos from Space
President Barack Obama speaks in front of the iconic Brandenburg Gate in Berlin Germany, Wednesday, June 19, 2013. (AP Photo/Pablo Martinez Monsivais)
WASHINGTON (AP) - President Barack Obama is planning a major push using executive powers to tackle the pollution blamed for global warming in an effort to make good on promises he made at the start of his second term. "We know we have to do more - and we will do more," Obama said Wednesday in Berlin.
Obama's senior energy and climate adviser, Heather Zichal, said the plan would boost energy efficiency of appliances and buildings, plus expand renewable energy. She also said the Environmental Protection Agency was preparing to use its authority under the Clean Air Act to regulate heat-trapping pollution from coal-fired power plants.
"The EPA has been working very hard on rules that focus specifically on greenhouse gases from the coal sector," Zichal said.
Zichal, speaking at a forum hosted by The New Republic in Washington, said that none of the proposals would require new funding or action from Congress. It has shown no appetite for legislation that would put a price on carbon dioxide after a White House-backed bill to set up a market-based system died in Obama's first term with Democrats in charge.
The plan, with details expected to be made public in coming weeks, comes as Obama has been under increasing pressure from environmental groups and lawmakers from states harmed by Superstorm Sandy to cut pollution from existing power plants, the largest source of climate-altering gases. Several major environmental groups and states have threatened to sue the administration to force cuts to power plant emissions. And just last week, former Vice President Al Gore, a prominent climate activist and fellow Democrat, pointedly called on Obama to go beyond "great words" to "great actions."
It was unclear whether the White House's plans would include controls on existing power plants. An administration official, who wasn't authorized to comment on the plan by name, said the White House was still weighing it. But since the administration has already proposed action on future power plants, the law would likely compel it to eventually tackle the remaining plants, or it would be forced to through litigation.
Obama's remarks in Berlin echoed comments he made in his State of the Union and inaugural speeches this year.
"This is the global threat of our time," Obama said Wednesday. "And for the sake of future generations, our generation must move toward a global compact to confront a changing climate before it is too late. That is our job. That is our task. We have to get to work."
Some environmentalists who cheered those remarks when they were made months ago, criticized them Wednesday.
"President Obama deserves praise for including climate change among the long-term threats facing us all," said Ned Helme, president of the Center for Clear Air Policy, an environmentally friendly think tank. "But he should do more than talk about the problem. The president needs to put the full force of his office behind new regulations that will truly curb greenhouse gas emissions. For too long now, he has produced little action. I'm encouraged that he will finally act and not just ask."
Meanwhile, the environmental community is growing impatient.
"I really can't understand why they haven't moved forward on this more quickly, and we hope that turns around," said Nathan Wilcox of Environment America.
An orchestrated and well-publicized campaign to persuade Obama to reject the Keystone XL oil pipeline, which would carry oil extracted from tar sands in western Canada to refineries along the Texas Gulf Coast, appears to be an uphill battle.
Opponents call the $7 billion project a "carbon bomb" that would carry "dirty oil" and exacerbate global warming. But the State Department in an environmental evaluation concluded that other means of transporting the oil would be worse from a climate perspective.
This radar image highlights portions of three of the lakes located in the Western Rift of the Great Rift Valley, a geological fault system of Southwest Asia and East Africa: Lake Edward (top), Lake Kivu (middle) and Lake Tanganyika (bottom). (Credit: ESA)
Arrays of sensors stretching across more than 1,500 miles in Africa are now probing the giant crack in the Earth located there - a fissure linked with human evolution - to discover why and how continents get ripped apart.
Over the course of millions of years, Earth's continents break up as they are slowly torn apart by the planet's tectonic forces. All the ocean basins on the Earth started as continental rifts, such as the Rio Grande rift in North America and Asia's Baikal rift in Siberia.
The giant rift in Eastern Africa was born when Arabia and Africa began pulling away from each other about 26 million to 29 million years ago. Although this rift has grown less than 1 inch (2.54 centimeters) per year, the dramatic results include the formation and ongoing spread of the Red Sea, as well as the East African Rift Valley, the landscape that might have been home to the first humans.
"Yet, in spite of numerous geophysical and geological studies, we still do not know much about the processes that tear open continents and form continental rifts," said researcher Stephen Gao, a seismologist at the Missouri University of Science and Technology in Rolla, Mo. This is partly because such research has mostly focused on mature segments of these chasms, as opposed to ones that are still in development, he explained. [Earth Quiz: Mysteries of the Blue Marble]
Geodynamic models suggest that below mature rifts, a region called the asthenosphere is upwelling. The asthenosphere is the hotter, weaker, upper part of the mantle that lies below the lithosphere, the planet's outer, rigid shell. So far, there are two contenders for what might cause this upwelling: anomalies deeper in the mantle or thinning of the lithosphere due to distant stresses.
To help find out which of the two different rifting models is correct, the Seismic Arrays for African Rift Initiation (SAFARI) project installed 50 seismic stations across Africa in the summer of 2012, each spaced about 17 to 50 miles (28 to 80 kilometers) apart.
"One of the techniques that we will use to image the Earth beneath the SAFARI stations is called seismic tomography, which is in principle similar to the X-ray CAT-scan technique used in hospitals," Gao told LiveScience's OurAmazingPlanet. "The only differences are that our sources of the 'rays' are earthquakes and man-made explosions, and the receivers are the seismic stations such as the 50 SAFARI stations."
Altogether, these arrays encompass a length of about 1,550 miles (2,500 km) and are located in four countries - Botswana, Malawi, Mozambique and Zambia.
"I think the project has a positive impact on local communities," Gao said. "Some of our 50 SAFARI seismic stations are on local schools, and the teachers and students were excited and were proud about the fact that their school was selected for a high-tech scientific instrument. We believe that this project showed some kids that the outside world is different and even fascinating."
The arrays will image the areas under the Okavango, Luangwa and Malawi rifts, the southwest and southernmost segments of the East African Rift system. These so-called incipient rifts are not yet mature and could thus shed light on why and how rifting occurs.
"This is the first large-scale project to image the structure and deformation beneath an incipient rift," Gao said. "The Okavango rift in Botswana is as young as a few tens-of-thousand years, while most other rifts such as the Rio Grande and Baikal rifts are as old as 35 million years."
Upwelling or thinning?
If thermal or dynamic anomalies deep in the mantle are responsible for rifting, then upwelling from the asthenosphere should already be occurring beneath these incipient rifts. In contrast, if thinning of the lithosphere is the cause of rifting, then any levels of upwelling should be insignificant because the lithosphere should not have thinned adequately for major upwelling to occur yet.
A magnitude-5.6 earthquake in November near the northern end of the Indian Ocean's mid-ocean ridge sent out seismic waves that were more than 1 second slower than predicted. This supports the idea that the mantle layer beneath Southern Africa is hotter than normal, perhaps due to a jet of magma known as a mantle plume that geologists have proposed exists beneath this area.
To image the structures beneath these rifts and pin down what the rifting mechanism in Eastern Africa is, researchers need data from more than just one event. The seismic arrays will be deployed for 24 months, and each station will sample the Earth for seismic waves 50 times per second.
"We are anxious to see if there are melted rocks in the mantle beneath the rifts, if there is convective mantle flow that is driving the rifting process, and how much the crust has been thinned in different portions of the rifts," Gao said. "But this cannot be done until next summer, when all the data recorded by SAFARI are processed."
The scientists detailed their findings to date in the June 11 issue of Eos, the online newspaper of the American Geophysical Union.
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Severe thunderstorms with the risk of a few tornadoes will advance eastward across the northern Plains and Upper Midwest into Friday.
Cities that could experience damaging and dangerous storms include Minot, Bismarck and Fargo, N.D.; Pierre, Huron and Sioux Falls, S.D.; Omaha, Neb.; and St. Cloud, Mankato and Minneapolis, Minn.
People whether at home, at work or on the road in this area should keep an eye out for rapidly changing weather conditions.
The storms bring the full spectrum of severe weather ranging from damaging wind gusts, frequent lightning strikes, large hail and flash flooding. A few of the strongest storms can produce a tornado.
The greatest threat of severe weather will shift from central and eastern Montana and the western part of North Dakota Wednesday to the eastern part of the Dakotas, eastern Nebraska and much of Minnesota Thursday.
During Friday, the risk for severe thunderstorms will expand eastward and southwestward.
The potential for severe weather into the weekend will continue over portions of the northern Plains and will expand eastward across more of the Great Lakes.
The severe weather will be firing as a couple of storm systems move along the Canada/U.S. border, while a zone of heat builds farther south over the Rockies and Plains.
RELATED: AccuWeather.com Severe Weather Center
Severe Storms from Montana to Alberta, Saskatchewan
Similar setups in the past have produced one or more large, strong thunderstorm complexes, and it is likely this event will have a similar outcome, especially Thursday night into Friday. However, forecasting the exact path such complexes will take can be challenging prior to their actual formation.
Regardless of whether or not a thunderstorm complex forms, individual thunderstorms can bring isolated severe weather and lines of thunderstorms can bring damage on a more regional basis.
While many seasoned residents in the northern Plains and the Upper Midwest have experience in severe weather situations, all residents and visitors should stay on top of the weather situation over the next few days.
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