الخميس، 17 سبتمبر 2015

Hidden superchain of volcanoes discovered in Australia

Scientists have just found the world's longest chain of volcanoes on a continent, hiding in plain sight.
The newly discovered Australian volcano chain isn't a complete surprise, though: Geologists have long known of small, separate chains of volcanic activity on the island continent. However, new research reveals a hidden hotspot once churned beneath regions with no signs of surface volcanism, connecting these separate strings of volcanoes into one megachain.
That 1,240-mile-long chain of fire spanned most of eastern Australia, from Hillsborough in the north, where rainforest meets the Great Barrier Reef, to the island of Tasmania in the south.
"The track is nearly three times the length of the famous Yellowstone hotspot track on the North American continent," Rhodri Davies, an earth scientist at Australian National University, said in a statement. [See Amazing Photos of the World's Wild Volcanoes]
String of volcanoes
Scientists had long known that four separate tracks of past volcanic activity fringed the eastern portion of Australia, with each showing distinctive signs of past volcanic activity, from vast lava fields to fields awash in a volcanic mineral called leucitite that's dark gray to black in color. Some of these regions were separated by hundreds of miles, leading geologists to think the areas weren't connected.
But Davies and his colleagues suspected that the Australian volcanism had a common source: a mantle plume that melted the crust as the Australian plate inched northward over millions of years. (Whereas many volcanoes form at the boundaries of tectonic plates, where hot magma seeps up through fissures in the Earth, others form when mantle plumes, or hot jets of magma, at the boundary between the mantle and Earth's core reach the surface.)
To bolster their hypothesis, Davis and his colleagues used the fraction of radioactive argon isotopes (versions of argon with different atomic weights) to estimate when volcanic activity first appeared in each of these regions. They combined this data with past work showing how the Australian plate had moved over the millennia. From this information, they could estimate where and when volcanism affected certain regions.
The team found that the same hotspot, likely from a mantle plume, was responsible for all of the volcanic activity crossing eastern Australia. The new volcanic chain, which the team dubbed the Cosgrove volcanic track, was formed between 9 million and 33 million years ago. (None of the volcanoes on Australia's mainland have been active during the recen past.)
However, there are large gaps in volcanic activity on the surface of this track. To understand why, the team modeled the thickness of the lithosphere, the stiff layer that forms the upper mantle and Earth's crust.

الأربعاء، 16 سبتمبر 2015

Double whammy: 2 meteors hit ancient Earth at the same time

It's not altogether uncommon to hear about double rainbows, but what about a double meteor strike? It's a rare event, but researchers in Sweden recently found evidence that two meteors smacked into Earth at the same time, about 458 million years ago.
Researchers from the University of Gothenburg uncovered two craters in the county of Jämtland in central Sweden. The meteors that formed the craterslanded just a few miles from each other at the same moment, according to Erik Sturkell, a professor of geophysics at the University of Gothenburg and one of the scientists who is studying the newfound craters.
When the meteors slammed into Earth, Jämtland was just a seafloor, about 1,600 feet below the surface of the water. One of the craters left by the meteors is huge, measuring 4.7 miles across. The other, smaller crater — which is only about 2,300 feet across — is located just 10 miles  from its larger neighbor. [Meteor Crater: Experience an Ancient Impact]
After analyzing information collected from a drilling operation, the researchers determined that the impact craters were formed at the same time. The information revealed identical geological sequences, or layers of rock, inside each crater. The sediment that accumulated inside the craters over the subsequent millennia also dates back to the same time, according to Sturkell.
"In other words, these are simultaneous impacts," Sturkell said in a statement. The meteors likely crashed to Earth following the collision of two large asteroids in the asteroid belt between Mars and Jupiter some 470 million years ago, he added.
When the meteors crashed into Earth, they displaced the water underneath them, leaving two huge, dry pits in the seabed for about 100 seconds, the researchers said.
"The water then rushed back in, bringing with it fragments from the meteorites mixed with material that had been ejected during the explosion and with the gigantic wave that tore away parts of the seabed," Sturkell said.
This isn't the first time that scientists in the area have found evidence of ancient meteor impacts in what is now Sweden, though it is the first time they've found evidence of two meteors striking the planet at the same moment.
In the 1940s, quarry workers found an unusual red slab of limestone on Kinnekulle, a large hill in the county of Västergötland in southern Sweden. Researchers later identified the red rock as a meteorite. While large meteorites typically "explode and disintegrate" upon impact with the ground, small meteors fall to Earth as rocks, like the one embedded in the limestone slab, Sturkell said.
About 90 meteorites in total have been found on Kinnekulle in the past 15 years alone. But in Jämtland, where the dual meteor strikes occurred, researchers have only found small grains of chromite, a remnant of large, exploded meteors.

الثلاثاء، 15 سبتمبر 2015

The cute and complicated science of raising twin pandas

The little panda was cold, low energy and having trouble breathing before its heart stopped beating. But the zoo baby left an indelible mark on its caretakers and admirers before it died, just days after being born to mother Mei Xiang, along with its brother. During its short life, the twin rode atop a lacrosse stick, snuggled with its mother and fed from a bottle, the last of which may have led to its demise.
The final necropsy results aren't complete, but the butter-stick-size panda likely died when fluid got into its lungs and caused inflammation, a condition called aspiration pneumonia. Veterinarians are unsure whether the cub got the condition during a bottle-feeding blunder or from formula it regurgitated, said Dr. Donald Neiffer, the chief veterinarian at Smithsonian's National Zoo.
"Whether or not the baby aspirated some of that [regurgitated] material or whether he aspirated material earlier in the day, we don't know, and we will never know," Neiffer told Live Science. [See Photos of Mei Xiang's New Twin Panda Cubs]
Express delivery
The pink and fuzzy cubs are part of a delicate plan, orchestrated on an international level, to preserve the giant panda species and, one day, introduce captive-bred pandas back into the wild. Just 1,864 giant pandas (Ailuropoda melanoleuca) exist in the wild, according to a 2015 panda census. An additional 395 of the roly-poly fur balls live in breeding centers and zoos around the world, said Devin Murphy, a spokesperson for Smithsonian's National Zoo.
Wild panda numbers increased by about 17 percent in the past decade, according to the 2015 census. American zoos are doing their part to breed and raise the animals, all on loan from China. Right now, there are 13 giant pandas in U.S. zoos, including San Diego Zoo, Memphis Zoo, Zoo Atlanta and the National Zoo.
The new twins were born to Mei Xiang (may-SHONG), the star mother at the National Zoo. Mei Xiang, whose name means "beautiful fragrance," has three surviving offspring, including Tai Shan (born in 2005), who now lives in China; Bao Bao (born in 2013), who lives at the National Zoo; and the surviving panda twin, which will be named 100 days after its birth.

الاثنين، 14 سبتمبر 2015

How armored dinosaur got its bone-bashing tail

Armored, squat, and built like a tank, ankylosaurs were a type of dinosaur known for their bony, protective exterior and distinct, sledgehammer-shaped tails. Now, scientists have pieced together how the animals' rear-end weapons evolved, finding that the hammer's "handle" came first.
Ankylosaurs were a group of bulky, tanklike dinosaurs with bony plates covering much of their bodies. Some of these animals — a subgroup known as ankylosaurids — also came equipped with a weaponized tail club as well.
"Ankylosaur tail clubs are made of two parts of the body," said study lead author Victoria Arbour, a postdoctoral researcher in the Department of Biological Sciences at North Carolina State University and the North Carolina Museum of Natural Sciences. "They're made of the bones of the tail — the vertebrae — that change so that they’re stiff and lock together in a really characteristic way. We call that the handle, like the handle of an ax. And the other part of the tail is the knob." [Paleo-Art: Dinos Come to Life in Stunning Illustrations]
The knob, or the large ball-type object at the end of the tail, was made of special bones called osteoderms, which actually formed in the skin, the researchers said.
Arbour was interested in examining what part of this weapon evolved first. Was it the handle or the knob? Or did they develop at the same time? "So as I was looking at ankylosaur fossils, for lots of different projects, I always kept an eye out for any evidence for some of those structures. Especially in older specimens I was looking at," she told Live Science.  
One of the fossils that caught Arbour's interest was the Gobisaurus, an ankylosaur that lived in Asia about 90 million years ago. The Gobisaurus' tail bones were fused and locked into a complete handle, but there was no knob at the end of its tail.
This provided a clue about the weapon's evolution, the researchers said. By comparing Gobisaurus with many other ankylosaur species and working them into a timeline, Arbour was able to show that the tails evolved handle-first. The researchers also used computer software to create a kind of family tree of ankylosaurs, which supported their findings.
This suggests that ankylosaurs started developing stiff tails as early as 120 million years ago. The knob was a more recent feature and didn't show up until about 75 million years ago, the researchers said.

الأحد، 13 سبتمبر 2015

Surprise! Newfound venomous spider drops in on scientists

Most people likely wouldn't react well to being surprised by a venomous spider, but recently, scientists at Booderee National Park, on the southern coast of Australia, were excited when a highly venomous funnel-web spider showed up unannounced.   
Many species of funnel-web spiders, named for their funnel-shaped webs, are indigenous to Australia, but only one of these species, the Sydney funnel-web spider, is known to live in Booderee National Park.
Sydney funnel-webs (Atrax robustus) are ground-dwelling spiders with highly venomous bites that, before the development of an anti-venom, posed a serious medical risk to humans. Funnel-webs, including Atrax robustus, were believed to be responsible for at least 13 deaths in Australia before the anti-venom became available, in 1981. [Creepy, Crawly & Incredible: Photos of Spiders]
But the spider found along Australia's southern coast by scientists from the Australian National University (ANU) wasn't Atrax robustus. In fact, it might be a brand-new species of funnel-web spider, said Thomas Wallenius, a biologist at ANU's Research School of Biology and one of the scientists who uncovered the arachnid.
"It's remarkable that we have found this other species in Booderee National Park. It shows we still have a lot to learn about what's out there in the bush," Walleniussaid in a statement.
The nearly 2-inch-long (50 millimeters) specimen is fairly large for a funnel-web spider, the researchers said. And unlike the Sydney funnel-web, this critter lives inside of fallen trees, not in underground burrows. This suggests that the newfound spider belongs to the genus Hadronyche, which consists of funnel-web spiders that are saproxylic, or dependent on dead or decaying wood for survival.
When Wallenius found the spider, it was burrowed in its "lair," a long web inside of a rotten log. 
"They build a silk-lined burrow inside the hollow log, which can be up to 2 meters [6.6 feet] long. She had probably been living in there for 25 to 30 years," Wallenius said.
That's right: Funnel-web spiders aren't just potentially deadly; they also live for an eerily long time. A study presented at the 22nd International Congress of Entomology in 2006 states that captive funnel-web spiders have a maximum life span of two decades.

السبت، 12 سبتمبر 2015

Bird mummy's secret: Why raptor was force-fed by ancient Egyptians

Its last meal wasn't pleasant.
A mouse tail was lodged in its throat when it died. Semi-digested flesh and fur still remained in its stomach when it was wrapped in mummy bandages.
A new autopsy reveals that overeating choked and killed this unfortunate raptor from ancient Egypt. Scientists suspect that Egyptians force-fed the bird so they could offer it to the sun god Ra as a votive mummy.
Mummification wasn't reserved for people in Egypt. The archaeological record is full of examples of cats, dogs, crocodiles and birds that were mummified and used as religious offerings to their corresponding animal gods, a practice that was popular from about 600 B.C. until around A.D. 250, well into the Roman period. Salima Ikram, a professor of Egyptology at the American University in Cairo, has made a living studying these animal mummies, and for her latest research, she examined the ancient remains of a European kestrel from the Iziko Museums of South Africa in Cape Town. [See Photos of Dog Mummies in Ancient Egyptian Catacomb]
New imaging technologies have made it possible to see through mummies without butchering ancient corpses: Ikram and her colleagues used an X-ray computed tomography scanner at Stellenbosch University in South Africa to see the insides of the kestrel in 3D. The images revealed the bird's stomach was stuffed with bones and teeth from at least two mice —one with its tail inside the raptor's esophagus —and a partially digested sparrow.
The kestrel's skeleton showed no signs of trauma. And whereas other bird mummies in Egypt had their gizzards removed or their beaks packed with food after death, this specimen also had no signs of evisceration. The kestrel was likely desiccated with natron (a naturally occurring soda ash) embalmed with resin and wrapped in bandages (in this case, quite haphazardly) with its stomach contents intact.
"We were extraordinarily surprised by the virtual autopsy as we had no expectation of any contents within the kestrel's body," Ikram said. "To learn that it choked was amazing."
Ikram and her colleagues say it's unlikely the kestrel accidentally or deliberately ate itself to death, as the birds are known to store food when they catch too much for a single meal. Rather, the bird likely had lots of help dying from its captors.

الجمعة، 11 سبتمبر 2015

Hummingbirds use hawks for home security

Tiny hummingbird nests, with their coffee-bean-size eggs, are a tempting treat for predators. But a new study finds that hummingbirds have evolved a clever approach to home security: They use hawks as guard dogs.
About 80 percent of the hummingbird nests built in the Chiricahua Mountains of Arizona are clustered near hawk nests, the researchers said. And location matters: When hummingbird nests are built near hawks, the nests have a daily survival rate of 31 percent. Outside of hawk territory, the daily survival rate drops to a mere 6 percent, one study found.
Harold Greeney, a biologist and the founder and director of the Yanayacu Biological Station Cosanga in Ecuador, and his colleagues first published that finding in The Wilson Journal of Ornithology in 2009. It wasn't the first time birds had been shown to nest near predators for protection, he told Live Science. [Gallery: Hummingbirds, Hawks & Predatory Jays]
"It wasn't anything particularly special until we went back and said, 'Well, we think that we showed that they do better there. The question now is, why?'" Greeney said.
The answer, it turns out, is that nesting hawks provide a "cone of safety" extending downward, Greeney and his colleagues report Sept. 4 in the journal Science Advances. Predatory jays that snatch hummingbird eggs avoid this cone to prevent becoming hawk food. (There are records of hawks eating hummingbirds in the wild, but the raptors prefer heartier snacks of large birds and rodents.)
"This is the first time anyone's figured out not just who all the players are, but exactly what it is about those players that's making [this] happen," Greeney said.
Stumbling on a discovery
Greeney and his team studied black-chinned hummingbirds (Archilochus alexandri) in the canyons and river valleys of the Chiricahua Mountains. Discovering that hummingbirds nest close to hawks was a matter of simply walking through the woods and making careful observations, Greeney said. 
"I sort of stumbled on to this, and then I stumbled onto more and stumbled onto a little more," he said. [Images: Beautiful Hummingbirds of the World]
At first, it wasn't clear that the hummingbirds were seeking out hawk nests for safety, Greeney said — maybe both species were simply picking choice nesting spots and clustering together by accident. He recorded the heights and locations of hawk nests, hummingbird nests and the activity of predators, from squirrels to Mexican jays (Ampelocoma wollweberi).
He hoped to see that hummingbird nests within a certain radius of hawk nests would get a survival boost. But when he first plotted the data, he found no such benefit.
"I thought, ugh, back to square one," Greeney said.
Fortunately, though, Greeney had thought like a bird. He hadn't just recorded the horizontal location of nests and predators; he'd recorded their height, too.
And height turned out to be key. The hawks in the area are two particularly agile species, the Cooper's hawk (Accipiter cooperii) and the northern goshawk (Accipiter gentilis). These hawks hunt by perching quietly and waiting for prey to pass below. They then plummet down, dodging tree branches and bringing death from above.
Jays are aware of the danger these hawks pose, so they avoid passing under their perches. As a result, they forage higher up in the forest canopy near hawk roosts. Thus, building within 984 feet of a hawk nest yields a survival rate of 19 percent for hummingbird nests — not bad compared with 6 percent survival rate seen with nests farther away from hawks. But building within the 560-foot radius "cone of safety" boosts the survival rate up to 52 percent, Greeney and his team found.

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