Paleontology news

A previously unknown giant volcanic eruption that led to global mass extinction 260 million years ago has been uncovered by scientists at the University of Leeds.

Unusually, scientists were able to pinpoint the exact timing of the eruption and directly link it to a mass extinction event in the study published in Science. This is because the eruptions occurred in a shallow sea – meaning that the lava appears today as a distinctive layer of igneous rock sandwiched between layers of sedimentary rock containing easily datable fossilised marine life.

The layer of fossilised rock directly after the eruption shows mass extinction of different life forms, clearly linking the onset of the eruptions with a major environmental catastrophe.

The global effect of the eruption is also due to the proximity of the volcano to a shallow sea. The collision of fast flowing lava with shallow sea water caused a violent explosion at the start of the eruptions – throwing huge quantities of sulphur dioxide into the stratosphere.

"When fast flowing, low viscosity magma meets shallow sea it's like throwing water into a chip pan – there's spectacular explosion producing gigantic clouds of steam," explains Professor Paul Wignall, a palaeontologist at the University of Leeds, and the lead author of the paper.

The injection of sulphur dioxide into the atmosphere would have lead to massive cloud formation spreading around the world - cooling the planet and ultimately resulting in a torrent of acid rain. Scientists estimate from the fossil record that the environmental disaster happened at the start of the eruption.

"The abrupt extinction of marine life we can clearly see in the fossil record firmly links giant volcanic eruptions with global environmental catastrophe, a correlation that has often been controversial," adds Professor Wignall.

Previous studies have linked increased carbon dioxide produced by volcanic eruptions with mass extinctions. However, because of the very long term warming effect that occurs with increased atmospheric carbon dioxide (as we see with current climate change) the causal link between global environmental changes and volcanic eruptions has been hard to confirm.

This work was done in collaboration with the Chinese University of Geosciences in Wuhan and funded by a grant from the Natural Environment Research Council, UK.

credited to University of Leeds (2009, May 30). Ancient Volcanic Eruptions Caused Global Mass Extinction. ScienceDaily. Retrieved May 31, 2009, from http://www.sciencedaily.com­/releases/2009/05/090528142827.htm

Famous depictions of the largest of all known dinosaurs, from film and television to museum skeletons, have almost certainly got it wrong, according to new research.

Recent depictions such as the BBC's Walking With Dinosaurs show them with their long necks held horizontal and their heads near the ground. But now scientists are saying the low-necked sauropod pose is a mistake: new evidence indicates that they held their necks aloft like giraffes and all other living land vertebrates, making them up to 15 metres tall.

Dr Mike Taylor and Dr Darren Naish, of the University of Portsmouth, and Dr Matt Wedel, of Western University of Health Sciences in California, argue that while sauropods could hold their necks low, it was not their habitual posture.

They studied X-rays of members of 10 different vertebrate groups and found that while the neck is only gently inclined in salamanders, turtles, lizards and crocodilians, it is vertical in mammals and birds – the only modern groups that share the upright leg posture of dinosaurs.

Dr Taylor said: “Like the animals we have with us today, they would have spent most of their time with their necks elevated, except when drinking or browsing at low levels.”

Modern vertebrates, from cats and humans to sauropods’ closest living relatives, the birds, hold their necks aloft in a vertical or near-vertical position.

Dr Wedel said: “We can’t just study fossil bones by themselves. Dinosaurs were living animals and to understand how they lived, we need to look at animals that are alive today. In this case, our evidence shows the present is the key to the past.”

The neck vertebrae of sauropods fit together mainly by way of ball and socket joints. In addition, the top part of each vertebra has a pair of facets, two at the front and two at the back, which glide past each other when the neck bends.

Dr Taylor said: “Scientists have assumed that each pair of facets must maintain at least a 50 percent overlap at all times; but looking at what ostriches and giraffes do, we see that their facets can slide much further, until they hardly overlap at all. This means that sauropods would have had a far greater range of neck movement than has been thought in recent times.

“Unless sauropods carried their heads and necks differently from every living vertebrate, we have to assume that the base of their neck was curved strongly upwards. In some sauropods this would have meant a graceful swan-like S-curve to the neck, and a look quite different from the recreations we are used to seeing today.”

Low necked poses for sauropods have been used for countless plastic toys and have become part of mainstream culture, thanks in part to the BBC’s Walking with Dinosaurs, and to new museum exhibits such as one at the American Museum of Natural History in New York.

Professor Mike Benton at Bristol University’s Department of Earth Sciences, said: “It's hugely important to understand how sauropod dinosaurs functioned. They were so huge – ten times the size of an elephant – and yet they were successful animals. This new work provides plausible evidence that sauropods held their necks elevated, rather than horizontally, as had been assumed.

“The new work is based on studies of living animals, but the next step will be to carry out engineering studies to see whether the new or old neck positions are energetically more efficient. If you have a long neck that weighs a tonne or more you must hold it in a neutral position where stresses and strains are minimised.”

credited to University of Portsmouth (2009, May 27). Giant Dinosaur Posture Is All Wrong: Sauropods Held Their Heads High, Research Finds. ScienceDaily. Retrieved May 28, 2009, from http://www.sciencedaily.com­ /releases/2009/05/090526213918.htm

A computer in antiquity would seem to be an anachronism, like Athena ordering takeout on her cellphone.

The Antikythera Mechanism, sometimes called the world’s first computer, has now been examined with the latest in high-resolution imaging systems and three-dimensional X-ray tomography. A team of British, Greek and American researchers was able to decipher many inscriptions and reconstruct the gear functions, revealing, they said, “an unexpected degree of technical sophistication for the period.”

The researchers, led by Tony Freeth and Mike G. Edmunds, both of the University of Cardiff, Wales, are reporting the results of their study in Thursday’s issue of the journal Nature.

They said their findings showed that the inscriptions related to lunar-solar motions and the gears were a mechanical representation of the irregularities of the Moon’s orbital course across the sky, as theorized by the astronomer Hipparchos. They established the date of the mechanism at 150-100 B.C.

The Roman ship carrying the artifacts sank off the island of Antikythera around 65 B.C. Some evidence suggests that the ship had sailed from Rhodes. The researchers speculated that Hipparchos, who lived on Rhodes, might have had a hand in designing the device.

In another article in the journal, a scholar not involved in the research, François Charette of the University of Munich museum, in Germany, said the new interpretation of the Antikythera Mechanism “is highly seductive and convincing in all of its details.” It is not the last word, he concluded, “but it does provide a new standard, and a wealth of fresh data, for future research.”

Historians of technology think the instrument is technically more complex than any known device for at least a millennium afterward.

The mechanism, presumably used in preparing calendars for seasons of planting and harvesting and fixing religious festivals, had at least 30, possibly 37, hand-cut bronze gear-wheels, the researchers reported. An ingenious pin-and-slot device connecting two gear-wheels induced variations in the representation of lunar motions according to the Hipparchos model of the Moon’s elliptical orbit around Earth.

The functions of the mechanism were determined by the numbers of teeth in the gears. The 53-tooth count of certain gears, the researchers said, was “powerful confirmation of our proposed model of Hipparchos’ lunar theory.”

The detailed imaging revealed more than twice as many inscriptions as had been recognized from earlier examinations. Some of these appeared to relate to planetary as well as lunar motions. Perhaps, the researchers said, the mechanism also had gearings to predict the positions of known planets.

Dr. Charette noted that more than 1,000 years elapsed before instruments of such complexity are known to have re-emerged. A few artifacts and some Arabic texts suggest that simpler geared calendrical devices had existed, particularly in Baghdad around A.D. 900.

It seems clear, Dr. Charette said, that “much of the mind-boggling technological sophistication available in some parts of the Hellenistic and Greco-Roman world was simply not transmitted further,” adding, “The gear-wheel, in this case, had to be reinvented.”

credited to nytimes.com

The mysterious disappearance of Everett Ruess, a 20-year-old artist, writer and footloose explorer who wandered the Southwest in the early 1930s on a burro and who has become a folk hero to many, has been solved with the help of University of Colorado at Boulder researchers and the National Geographic Society. The short, compelling life of Ruess, who went missing in 1934 after leaving the town of Escalante, Utah, has been the subject of much speculation. His story has spawned two documentary films, as well as plays, books, magazine and newspaper articles and a T-shirt line, and his name now graces an annual art festival in Escalante.

An investigative article in the April/May issue of National Geographic Adventure by David Roberts, who had been probing the Ruess disappearance for years, indicates a Navajo man, Aneth Nez, told his granddaughter, Daisy Johnson, in 1971 that he witnessed the murder of a young white man near Bluff, Utah, in the 1930s by Ute Indians. Nez told her he buried the body in a crevasse on nearby Comb Ridge.

Roberts reported that in May 2008, Denny Belson, grandson of Nez and sister of Johnson, located the burial site and contacted the FBI in Monticello, Utah. FBI investigators then visited the site and took photographs. The enterprising Belson used a Google search using the keywords "missing persons," "1930s," and "Arizona/Utah," and came across stories about the disappearance and speculation about Ruess, said Roberts.

Roberts contacted Ron Maldano, the supervisory archaeologist at the Cultural Resource Compliance Section of the Navajo Nation based in Chimney Rock, Ariz. Maldano conducted a detailed examination of the burial site and determined the remains were likely Caucasian. Roberts put him in touch with two nieces and two nephews of Ruess for mitochondrial DNA samples, which proved inconclusive.

Roberts then contacted CU-Boulder anthropology Professor Dennis Van Gerven, who traveled to the site with doctoral student Paul Sandberg with the support of the National Geographic Society, excavated the remains, and returned with them to CU-Boulder with the permission of the Ruess family.

An analysis of teeth and bones by Van Gerven and Sandberg were used to determine the sex, age and stature of the person. Wisdom tooth eruption, pelvic structure, bone growth markers and femur length indicated it was a male roughly 20 years old and about 5 feet 8 inches tall -- a virtual match for Ruess, said Van Gerven.

The CU-Boulder researchers began a painstaking reconstruction of the fragile facial bones, stabilizing them on a ball of clay. Sandberg used Adobe Photoshop to superimpose photos he took of the remade face onto a frontal portrait of a smiling Ruess and a profile portrait of him, both taken in the 1930s by Lange.

"The next step was to match two points on the photos of the bones to their respective positions on the portraits," Sandberg said. "If the other anatomical points did not match, we could exclude Ruess. But all the points fell into place. The jaw fit, the curve of the nasal bones fit, the rim of the eye orbit fit and the bridge of the nose fit."

The most compelling piece of evidence was the teeth, he said. "Once a single tooth was scaled into position, the size and shape of the other teeth, as well as the morphology of the face above the teeth, matched the portrait. The correspondence was striking," Sandberg said.

"We spent a lot of time making certain that the skeletal images superimposed on the Lange photos remained anatomically exact and were in no way altered by the technique," said Van Gerven.

"But we wound up with a constellation of evidence that was a remarkable match to Ruess," he said. "We had a male about 20 years old, 5 feet 8 inches tall with facial bones that precisely matched the photographs. We concluded it was very, very unlikely that this was not Everett Ruess. But we also knew the final arbiter in this case would be genetic testing."

Van Gerven contacted CU-Boulder molecular, cellular and developmental biology Professor Kenneth Krauter, an expert in DNA analysis. Krauter brought in CU-Boulder research assistant Helen Marshall, who had extensive experience working with DNA. Marshall took two small femur fragments and prepared them by grinding and liquefying them, subsequently extracting, purifying and amplifying DNA samples.

The team members used techniques developed as a byproduct of the Human Genome Project that permitted them to assess the passing of DNA markers from one generation to the next. "We used the most stringent protocols and standards available," said Marshall. "The results were totally blind in the sense that the computer doesn't have an opinion in terms of the DNA marker matches."

High-tech "gene chips," or microarrays, made by Affymetrix Corp., a global company headquartered in Santa Clara, Calif., provided Krauter and Marshall with 600,000 separate DNA markers from the femur DNA. These were compared with roughly the same number of DNA markers extracted from saliva samples taken from the two nieces and two nephews of Ruess. As an added precaution, the team also compared the markers with the DNA of 50 people around the world.

CU-Boulder Assistant Professor Matthew McQueen of CU-Boulder's Institute for Behavioral Genetics, consulting with experts at Oxford University in England, statistically analyzed the data. The results showed the nieces and nephews of Ruess -- all siblings -- shared about 50 percent of the genetic markers with each other, and all four shared about 25 percent of the DNA markers from the femur bone samples. The results from the DNA comparisons from the 50 random people from around the world showed a less than 1 percent match, said Krauter.

"It was almost exactly what geneticists would expect when comparing DNA between nieces and nephews and an uncle or an aunt," said Krauter. "This is entirely consistent with the hypothesis that the bones are those of Everett Ruess, and make it virtually impossible that the bones are from an unrelated individual.

"The combination of the forensic analysis and the genetic analysis makes it an open and shut case," Krauter said. "I believe it would hold up in any court in the country."

The wandering spirit of Ruess, whom author Wallace Stegner once compared to a young John Muir, appears to have finally come to rest. The family of Ruess plans to have the remains cremated and scattered over the Pacific Ocean. Case closed.

credited to esciencenews.com

The legend is that the great rulers of Canaan, the ancient land of Israel, were all men. But a recent dig by Tel Aviv University archaeologists at Tel Beth-Shemesh uncovered possible evidence of a mysterious female ruler.

"The big question became, 'What city did she rule?'" Dr. Lederman and Prof. Bunimovitz say. The archaeologists believe that she ruled as king (rather than "queen," which at the time described the wife of a male king) over a city of about 1,500 residents. A few years ago, Tel Aviv University's Prof. Nadav Naaman suggested that she might have ruled the city of Beth Shemesh. But there has been no proof until now.

"The city had been violently destroyed, in a way we rarely see in archaeology," says Prof. Bunimovitz, who points to many exotic finds buried under the destruction, including an Egyptian royal seal, bronze arrowheads and complete large storage vessels. They suggest a large and important city-state, well enmeshed within East Mediterranean geo-political and economic networks.

"It was a very well-to-do city," says Lederman. "Strangely, such extensive destruction, like what we found in our most recent dig, is a great joy for archaeologists because people would not have had time to take their belongings. They left everything in their houses. The site is loaded with finds," he says, adding that the expensive items found in the recent level points to it as one the most important inland Canaanite cities.

Archaeologists digging on Jerusalem's Mount of Olives have discovered a nearly 3,000-year-old jar handle bearing ancient Hebrew script, a find significantly older than most inscribed artifacts unearthed in the ancient city, an archaeologist said.

The Iron Age handle is inscribed with the Hebrew name Menachem, which was the name of an Israelite king and is still common among Jews.

The inscription also includes a partly intact letter, the Hebrew character "lamed," meaning "to." That suggests the jar was a gift to someone named Menachem, said Ron Beeri, who directed the excavation for the Israel Antiquities Authority. There is no indication the inscription refers to the king himself.

The name and similar variants have been found on Egyptian pottery dating back 3,500 years, and the Bible lists Menachem Ben Gadi as an ancient king of Israel. But this is the first time an artifact bearing the name has been unearthed in Jerusalem, Beeri said.

"It's important because it shows that they actually used the name Menachem during that period," Beeri said. "It's not just from the Bible, but it's also in the archaeological record."

Based on the style of the inscription, he dated the handle to around 900 B.C., the time of the first Jewish Temple in Jerusalem as recounted in the Bible.

The vessel the handle was attached to did not survive, so it is impossible to tell what it was used for, Beeri said. Similar vessels were known to have held products like oil or wheat.

Construction workers uncovered the archaeological site while digging the foundation for a girl's school being built in the area, Beeri said.

Excavators also uncovered storage vessels and implements from two earlier nomadic settlements, both dating to around 2,000 B.C., he said, as well as artifacts dating from the time of the Roman Empire around 2,000 years ago.

Archaeologists have completed their dig, and construction workers building the school are back on the job, Beeri said.

The Mount of Olives is just outside Jerusalem's Old City. The hill is important to Jews because of its proximity to the destroyed Temple and to Christians, who believe it is the site where Jesus ascended to heaven.

credited to msnbc.msn.com

Meet "Ida," the small "missing link" fossil that's created a big media splash and will likely continue to make waves among those who study human origins.

In a new book, documentary, and promotional Web site, paleontologist Jorn Hurum, who led the team that analyzed the 47-million-year-old fossil seen above, suggests Ida is a critical "missing link" species in primate evolution.

The fossil, he says, bridges the evolutionary split between higher primates such as monkeys, apes, and humans and their more distant relatives such as lemurs.

"This is the first link to all humans," Hurum, of the Natural History Museum in Oslo, Norway, said in a statement. Ida represents "the closest thing we can get to a direct ancestor."

Ida, properly known as Darwinius masillae, has a unique anatomy. The lemur-like skeleton features primate-like characteristics, including grasping hands, opposable thumbs, clawless digits with nails, and relatively short limbs.

"This specimen looks like a really early fossil monkey that belongs to the group that includes us," said Brian Richmond, a biological anthropologist at George Washington University in Washington, D.C., who was not involved in the study.

But there's a big gap in the fossil record from this time period, Richmond noted. Researchers are unsure when and where the primate group that includes monkeys, apes, and humans split from the other group of primates that includes lemurs.

"[Ida] is one of the important branching points on the evolutionary tree," Richmond said, "but it's not the only branching point."

At least one aspect of Ida is unquestionably unique: her incredible preservation, unheard of in specimens from the Eocene era, when early primates underwent a period of rapid evolution.

"From this time period there are very few fossils, and they tend to be an isolated tooth here or maybe a tailbone there," Richmond explained. "So you can't say a whole lot of what that [type of fossil] represents in terms of evolutionary history or biology."

In Ida's case, scientists were able to examine fossil evidence of fur and soft tissue and even picked through the remains of her last meal: fruits, seeds, and leaves.

What's more, the newly described fossil was unearthed in Germany's Messel Pit. Ida's European origins are intriguing, Richmond said, because they could suggest—contrary to common assumptions—that the continent was an important area for primate evolution.

credited to news.nationalgeography.com

The discovery of a gruesome feeding frenzy that played out 73 million years ago in northwestern Alberta may also lead to the discovery of new dinosaur species there.

Miyashita and Fanti came across a nesting site and found the remains of baby, plant-eating dinosaurs and the teeth of a predator. The researchers matched the teeth to a Troodon, a raptor-like dinosaur about two metres in length. This finding has opened new doors in dinosaur research on this part of the continent: "It established that dinosaurs were nesting at this high latitude," said Miyashita. "It also shows for the first time a significant number of Troodons in the area [who] hunted hatchling dinosaurs."

Over the course of two summers of field work Miyashita and Fanti began building a theory that Grande Prairie is a "missing link" between known dinosaur species that existed much further to the north and south. "Prior to this there were no localities with a variety of dinosaurs and other animals between Alaska and southern Alberta," said Myiashita. The list of new finds for the area includes armoured and thick-headed plant eaters and fossilized freshwater fish and reptiles.

Miyashita says this small pocket of previously undiscovered life could have had interactions that lead to the evolution of new species.

"New dinosaurs weren't created by interbreeding," said Miyashita. "Having a variety of dinosaurs in one area creates new ecological interactions such as competition for food and predation.

"That can lead to the evolution of a new species."

One Grande Prairie dinosaur the researchers suspect is a new species is the Duck bill. Miyashita says unlike the Duck bill found further north in Alaska, the Grande Prairie has a visible bump or crest on its forehead. The pair will go back to Grande Prairie area in 2010 to focus on finding other dinosaur species in the area.

credited to University of Alberta (2009, May 15). Competition May Have Led To New Dinosaur Species In Northwestern Alberta. ScienceDaily. Retrieved May 18, 2009, from http://www.sciencedaily.com­ /releases/2009/05/090512134657.htm

Long-necked dinosaurs didn't graze treetops, according to new research that suggests the prehistoric animals were better off holding their necks horizontal, not upright.

Since long-necked modern animals, such as giraffes, tend to browse on leaves in tall trees, paleontologists have assumed that sauropods—whose necks could be as long as 30 feet [9 meters]—must have done the same.

But Roger Seymour, of the University of Adelaide in Australia, found that sauropods would have spent as much as 75 percent of their bodies' energy to keep their heads held high.

Most mammals use about 10 percent of their energy to circulate blood through their bodies. Giraffes use about 18 percent of their energy to keep blood moving through their long, upright necks.

"Would the increased availability of food in tall trees be worth the cost? This seems doubtful," Seymour said. "It would probably make more energetic sense for [sauropods] to feed with their necks close to horizontal."

By moving their necks side-to-side horizontally, sauropods would have been able to feed on a very large area of plant material without having to move their bodies.

That may not seem like a much of an energy-saving tactic. But in animals that may have weighed 30 to 40 tons, the energetic difference between taking a few steps and not taking a few steps may have been as huge as the animals themselves.

Expensive Treats

Still, some scientists not involved with Seymour's research argue that, in extreme cases, it may have been worth it for saurpods to spend the extra energy to lift their necks.

The bones and joints in some of these animals show that they could lift their necks between 30 and 60 degrees above horizontal, paleontologist Martin Sander, of the University of Bonn in Germany, said.

When food availability at low and medium heights became scarce, the cost of raising the head to get valuable resources may have been worth it, Sander said.

Richard Cowen, of the University of California, Davis, noted that other animals sometimes expend enormous amounts of energy on food.

Cheetahs, for example, sprint after prey, even though the big cats only make the catch one time in four. Likewise, whales use massive amounts of energy to dive deep into cold water, and migratory birds burn heaps of energy flying thousands of miles.

All of these behaviors could be viewed as incredible energy sinks, but we know they are not because the animals gain something significant in return that makes the energy expenditure worth it, Cowen explained.

"It would be reasonable for sauropods to browse occasionally with heads high, as long as the payoff was also high," Cowen said.

credited to news.nationalgeographic.com

An island for ancient elites has been found in central Mexico, archaeologists say. Among the ruins are a treasury and a small pyramid that may have been used for rituals.

"If you would paddle up to the island [during the time], you would see a number of buildings, some temples with smoke coming out of them from rituals, and a small village of specialized people—priests, elites," Fisher said.

The Purépecha people—named Tarascan by the Spanish—were formidable enemies with their neighbors, the Aztec. From their powerful capital city and religious center Tzintzuntzan, the Tarascans successfully thwarted every attack by the Aztec.

Tarascan people valued such products as honey, cotton, feathers, and salt, and they often expanded into neighboring lands in search of these goods.

Ritual Center

Fisher and colleagues found a square structure with a formal entrance that is believed to have been an imperial treasury.

Adjacent to the treasury is a small pyramid, which has large, open rooms that would have been suitable for ritual activity. Pipe fragments were also found near the treasury.

The pipe discoveries may bear out ritual descriptions on a previously found ancient Spanish scroll.

The scroll shows people smoking pipes and drinking pulque—a drink made of agave, a crucial crop used for alcoholic drinks, such as tequila, and syrup, Fisher said.

The scroll also describes ritual treasury caches dedicated to specific gods.

"These caches were also used to finance activities like warfare," said Fisher, who has submitted a report describing his as yet unpublished research to Mexico's National Institute of Anthropology and History.

Toward the end of the island's Tarascan occupation, the area was a "ritual center" where people of elite status lived and worked, he added.

The team identified a colonial-era chapel from the early 1500s, built in the first 20 years of the Spanish conquest.

Evidence of crop cultivation also suggests that humans continuously occupied the site for 2,000 years, Fisher said.

The entire island was covered in agricultural terraces, possibly to grow agave.

People created the terraces by digging sections of land about 6.6 feet (2 meters) wide, with earthen walls and a ditch on either side.

Filling in Gaps

"The discovery fills in gaps in the Lake Pátzcuaro basin's chronology," said Helen Perlstein Pollard, professor of anthropology at Michigan State University who has worked with Fisher in Mexico's Tarascan region.

"He discovered the basic sequence of occupation, the repeated use of this island over time, and the way the use of the island has shifted over time," Perlstein Pollard said.

Now, archaeologists can begin to examine the relationship between settlement patterns and the economic and political structures on the islands.

"We can now begin to ask the interesting questions," she said.

credited to news.nationalgeographic.com

The story endures as a classic in the genre of lost worlds long vanished, the ruins and treasures of which are surely somewhere out there yet to be found. Legends, though, are often mirages, forever shimmering out of reach, yet exerting an attractive power beyond reason.

Sometimes the pursuit of legends leads to unforeseen knowledge.

In the 12th century A.D., the legend of Prester John, a rich and powerful Christian monarch somewhere in Asia, drew intrepid seekers, eventually including Marco Polo, who opened Western eyes to the wonders of the East. When no one found Prester John in Asia, the legend did not go away; its locale shifted to Africa.

The golden city of El Dorado eluded hellbent adventurers, whose frustrated quest nonetheless put much of South America on the map.

The fabled Seven Cities of Cibola, castles in the air that proved to be nothing more than humble Indian pueblos, drew Europeans across tortured miles and years of discovery in what is now the Southwestern United States.

The tale of the lost continent has sent respected classical scholars to their texts for corroboration that Atlantis was more than fantasy. Archaeologists, geologists and divers have plumbed ocean depths where the island supposedly sank out of sight thousands of years ago. Not a scrap of compelling evidence supporting the legend has ever turned up.

Such a negative discovery might be conclusive enough for most legends to pass from rock-hard belief to literary artifacts of prescientific cultures living in a world of limited horizons and boundless mystery. But true believers, complaining that scientists have got it all wrong, continue the search.

Generations of adventurers, writers, mystics and cranks have satisfied themselves of the legend's reality. Their ''solutions'' fill more than 2,000 books and countless articles. The lost continent also inspired works by authors as diverse as Francis Bacon and Arthur Conan Doyle, and Hollywood has weighed in with any number of forgettable movies.

Richard Ellis, author of ''Imagining Atlantis,'' thinks the legend is fantasy. ''Atlantis lives on in people's minds largely because you cannot prove it doesn't exist,'' he said recently. ''You can't search every inch of the ocean bottom, and so the hope remains alive and the promise of finding treasures in sunken palaces.''

The sole source of the Atlantis story is by no means obscure. In two dialogues, the ''Critias'' and the ''Timaeus,'' Plato in the fourth century B.C. described a resplendent island empire in the Atlantic Ocean beyond the Pillars of Hercules (the Strait of Gibraltar). ''This dynasty, gathering its whole power together,'' Plato wrote, ''attempted to enslave, at a single stroke, your country and ours.''

Even after disbelief in ancient gods undercut literal acceptance of the legend, medieval maps were sprinkled with imaginary islands in the Atlantic, including Antillia. Some experts suspect this preserves in garbled form the name of Atlantis and a lingering belief that its remnants may still exist. The maps encouraged navigators in their quests, among them Columbus.

The 20th century was hard on Atlantis dreams. Detailed mapping of the sea floor and the new theory of plate tectonics made it clear, geophysicists say, that land masses resembling Atlantis never existed in the Atlantic.

Undeterred, ardent believers went looking elsewhere: in Scandinavia, the Bahamas and the Aegean Sea. Huge blocks of stone submerged off Cuba were recently proclaimed possible ruins of the lost empire.

A more plausible hypothesis, some scholars think, places Atlantis at Crete. The accomplished Minoan civilization there collapsed in the middle of the second millennium B.C., presumably destroyed by a volcanic eruption on nearby Thera, modern Santorini.

Was this in Plato's mind? Or he might have been inspired by an event in his own time, the earthquake in 373 B.C. that brought the Greek city of Helike, as ancient writers said, crashing into the sea.

The unknown fires the imagination. Whether the starry night or extraterrestrial beings, the mystery of life itself or life after death or any of the uncertain boundaries between reality and resolute yearning, it is unknowns that populate history with gods and heroes, monsters of the deep and chimeric islands, lost paradises and the elusive El Dorado at the end of greed's rainbow, not to mention Martians.

Some mysteries will be solved, but never all of them. As for Atlantis, another Greek philosopher delivered the verdict that has yet to be contradicted.

As noted by the British classicist J. V. Luce, Aristotle considered Atlantis a poetic fiction invented by Plato as a warning of the fate that befalls the arrogant and decadent. Plato placed Atlantis beyond the then known world and sank it to the ocean floor to preserve the power of the mystery.

''The man who dreamed it up made it vanish'' was Aristotle's solution to the mystery of Atlantis.

credited to nytimes.com

Geologists may have uncovered the answer to an age-old question - an ice-age-old question, that is. It appears that Earth's earliest ice ages may have been due to the rise of oxygen in Earth's atmosphere, which consumed atmospheric greenhouse gases and chilled the earth.

"We can now put our hands on the rock library that preserves evidence of irreversible atmospheric change," said Kaufman. "This singular event had a profound effect on the climate, and also on life."

Using sulfur isotopes to determine the oxygen content of ~2.3 billion year-old rocks in the Transvaal Supergroup in South Africa, they found evidence of a sudden increase in atmospheric oxygen that broadly coincided with physical evidence of glacial debris, and geochemical evidence of a new world-order for the carbon cycle.

"The sulfur isotope change we recorded coincided with the first known anomaly in the carbon cycle. This may have resulted from the diversification of photosynthetic life that produced the oxygen that changed the atmosphere," Kaufman said.

Two and a half billion years ago, before the Earth's atmosphere contained appreciable oxygen, photosynthetic bacteria gave off oxygen that first likely oxygenated the surface of the ocean, and only later the atmosphere. The first formed oxygen reacted with iron in the oceans, creating iron oxides that settled to the ocean floor in sediments called banded iron-formations - layered deposits of red-brown rock that accumulated in ocean basins around the worldwide. Later, once the iron was used up, oxygen escaped from the oceans and started filling up the atmosphere.

Once oxygen made it into the atmosphere, Kaufman's team suggests that it reacted with methane, a powerful greenhouse gas, to form carbon dioxide, which is 62 times less effective at warming the surface of the planet. "With less warming potential, surface temperatures may have plummeted, resulting in globe-encompassing glaciers and sea ice" said Kaufman.

In addition to its affect on climate, the rise in oxygen stimulated the rise in stratospheric ozone, our global sunscreen. This gas layer, which lies between 12 and 30 miles above the surface, decreased the amount of damaging ultraviolet sunrays reaching the oceans, allowing photosynthetic organisms that previously lived deeper down, to move up to the surface, and hence increase their output of oxygen, further building up stratospheric ozone.

"New oxygen in the atmosphere would also have stimulated weathering processes, delivering more nutrients to the seas, and may have also pushed biological evolution towards eukaryotes, which require free oxygen for important biosynthetic pathways," said Kaufman.

The result of the Great Oxidation Event, according to Kaufman and his colleagues, was a complete transformation of Earth's atmosphere, of its climate, and of the life that populated its surface. The study is published in the May issue of Geology.

credited to sciencedaily.com

The great splat of an asteroid that might have wiped out the dinosaurs apparently didn't get all of them. New fossil evidence suggests some dinosaurs survived for up to half a million years after the impact in remote parts of New Mexico and Colorado.

Scientists recently analyzed dinosaur bones found in the Ojo Alamo Sandstone in the San Juan Basin. Based on detailed chemical investigations of the bones, and evidence for the age of the rocks in which they are found, the researchers think some dinosaurs outlived the crash that occurred 65 million years ago and stuck around for a while.

"This is a controversial conclusion, and many paleontologists will remain skeptical," said David Polly, one of the editors of the journal Palaeontologia Electronica, in which the research was published today.

Lead researcher Jim Fassett of the U. S. Geological Survey in Santa Fe, New Mexico went to great lengths to establish when the bones originated.

"The great difficulty with this hypothesis — that these are the remains of dinosaurs that survived — is ruling out the possibility that the bones date from before the extinction," he said. "After being killed and deposited in sands and muds, it is possible for bones to be exhumed by rivers and then incorporated into younger rocks."

To try to eliminate that scenario, Fassett investigated the rocks surrounding the bones and studied date indicators, such as their magnetic polarity. He said the evidence "independently indicate[s] that they do indeed post-date the extinction."

He also found that the dinosaur bones from the Ojo Alamo Sandstone have distinctly different concentrations of rare earth metal elements than the deeper, older rocks that date from the time of the impact. This suggests that it's unlikely the bones originated in that older rock and were somehow relocated to the more recent, higher level of sediment.

Another piece of evidence seems to support the claim, too. The fossil remains include a group of 34 hadrosaur bones lying together, which Fassett said are "doubtless from a single animal." If the bones had been exhumed from the older rock by a river, they would have likely been scattered in several locations, and wouldn't be clustered together as they are.

Even if the dinosaur bones do turn out to belong to disaster survivors, there probably were very few of them compared to their population before the crash.

"One thing is certain," Polly said. "If dinosaurs did survive, they were not as widespread as they were before the end of the Cretaceous and did not persist for long."

The enduringly popular theory that the Chicxulub crater holds the clue to the demise of the dinosaurs, along with some 65 percent of all species 65 million years ago, is challenged in a paper to be published in the Journal of the Geological Society on April 27, 2009.

When spherules from the impact were found just below the Cretaceous-Tertiary (K-T) boundary, it was quickly identified as the "smoking gun" responsible for the mass extinction event that took place 65 million years ago.

It was this event which saw the demise of dinosaurs, along with countless other plant and animal species.

However, a number of scientists have since disagreed with this interpretation.

The newest research, led by Gerta Keller of Princeton University in New Jersey, and Thierry Adatte of the University of Lausanne, Switzerland, uses evidence from Mexico to suggest that the Chicxulub impact predates the K-T boundary by as much as 300,000 years.

"Keller and colleagues continue to amass detailed stratigraphic information supporting new thinking about the Chicxulub impact, and the mass extinction at the end of the Cretaceous," says H. Richard Lane, program director in the National Science Foundation (NSF)'s Division of Earth Sciences, which funded the research. "The two may not be linked after all."

From El Penon and other localities in Mexico, says Keller, "we know that between four and nine meters of sediments were deposited at about two to three centimeters per thousand years after the impact. The mass extinction level can be seen in the sediments above this interval."

Advocates of the Chicxulub impact theory suggest that the impact crater and the mass extinction event only appear far apart in the sedimentary record because of earthquake or tsunami disturbance that resulted from the impact of the asteroid.

"The problem with the tsunami interpretation," says Keller, "is that this sandstone complex was not deposited over hours or days by a tsunami. Deposition occurred over a very long time period."

The study found that the sediments separating the two events were characteristic of normal sedimentation, with burrows formed by creatures colonizing the ocean floor, erosion and transportation of sediments, and no evidence of structural disturbance.

The scientists also found evidence that the Chicxulub impact didn't have the dramatic impact on species diversity that has been suggested.

At one site at El Penon, the researchers found 52 species present in sediments below the impact spherule layer, and counted all 52 still present in layers above the spherules.

"We found that not a single species went extinct as a result of the Chicxulub impact," says Keller.

This conclusion should not come as too great a surprise, she says. None of the other great mass extinctions are associated with an impact, and no other large craters are known to have caused a significant extinction event.

Keller suggests that the massive volcanic eruptions at the Deccan Traps in India may be responsible for the extinction, releasing huge amounts of dust and gases that could have blocked out sunlight and brought about a significant greenhouse effect.

credited to National Science Foundation (2009, April 28). New Blow Against Dinosaur-killing Asteroid Theory, Geologists Find. ScienceDaily. Retrieved May 5, 2009, from http://www.sciencedaily.com­ /releases/2009/04/090427010803.htm