Tag: Plos one

Exodus Hydrodynamics: How the East Winds Parted the Red Sea

splitting the red sea according to hydrodynamicsThe biblical narrative of the crossing of the Red Sea has inspired and mystified people for millennia. So far, Archeologists and Egyptologists have found little direct evidence to substantiate many of the events described in Exodus, said to have taken place more than 3,000 years ago.

Now, a new study offers a new hydrodynamic explanation for the miracle a strong east wind, blowing overnight, could have created a land bridge (watch the video) and allowed for passage.

By pinpointing a possible site south of the Mediterranean Sea for the crossing, the study – based on a reconstruction of the likely locations and depths of Nile delta waterways, which have shifted considerably over time – could benefit experts seeking to research whether splitting of the Red Sea ever took place.

The computer model shows the winds pushing the water back at a bend where an ancient river is believed to have merged with a coastal lagoon – named the ‘Lake of Tanis’ by Herodotus – along the Mediterranean Sea. With the water pushed back into both waterways, a land bridge would have opened at the bend, enabling people to walk across exposed mud flats to safety. As soon as the wind died down, the waters would have rushed back in.

“The simulations match fairly closely with the account in Exodus,” says Carl Drews of the National Center for Atmospheric Research. “The parting of the waters can be understood through fluid dynamics. The wind moves the water in a way that’s in accordance with physical laws, creating a safe passage with water on two sides and then abruptly allowing the water to rush back in.”

Splitting the Red Sea? Map with Lake Tanis

The computer simulations by Carl Drews and University of Colorado at Boulder (CU) oceanographer Weiqing Han are intended to present a possible scenario of events.

The book of Exocus describes Moses and the fleeing Israelites trapped between the Pharaoh’s advancing chariots and a body of water that has been variously translated as the Red Sea or the Sea of Reeds. Although the biblical account attributes the splitting of the waters to the Lord’s power, it includes an east wind as natural component in the chain of events.

Then Moses stretched out his hand over the sea, and the Lord drove the sea back by a strong east wind all night and made the sea dry land, and the waters were divided. And the people of Israel went into the midst of the sea on dry ground, the waters being a wall to them on their right hand and on their left.

James Rennell's reconstruction of the Nile delta according to Herodotus

This enables the Israelites to flee to the other shore. When when the Pharaoh’s army attempts to pursue them in the morning, the waters rush back and drown the soldiers.

Reconstructing ancient topography

Studying maps of the ancient topography of the Nile delta, the researchers found an alternative site for the crossing about 75 miles north of the Suez reef and just south of the Mediterranean Sea.

Although there are uncertainties about the waterways of the time, some oceanographers believe that an ancient branch of the Nile River flowed into a coastal lagoon then known as the Lake of Tanis.

The two waterways would have come together to form a U-shaped curve.

Analysis of archeological records, satellite measurements, and current-day maps enabled the research team to estimate the water flow and depth that may have existed 3,000 years ago.

Using an ocean computer model to simulate the impact of an overnight wind at that site, the researchers found that a wind of 63 miles an hour, lasting for 12 hours, would have pushed back waters estimated to be six feet deep. This would have exposed mud flats for four hours, creating a dry passage about 2 to 2.5 miles long and 3 miles wide. The water would be pushed back into both the lake and the channel of the river, creating barriers of water on both sides of newly exposed mud flats.

As soon as the winds stopped, the waters would come rushing back, much like a tidal bore. Anyone still on the mud flats would be at risk of drowning.

Video: The Physics of a Land Bridge

Sustained winds can cause an event known as a wind setdown, in which water levels are temporarily lowered. This computer animation (by Tim Scheitlin and Ryan McVeigh, NCAR) shows how a strong east wind over the Nile Delta could have pushed water back into ancient waterways after blowing for about nine hours, exposing mud flats and possibly providing an overland escape route similar to the biblical account of the Red Sea parting.

The set of 14 computer model simulations also showed that dry land could have been exposed in two nearby sites during a windstorm from the east.

However, those sites contained only a single body of water and the wind would have pushed the water to one side rather than creating a dry passage through two areas of water.

“People have always been fascinated by this Exodus story, wondering if it comes from historical facts,” Drews says. “What this study shows is that the description of the waters parting indeed has a basis in physical laws.”

Alternative Theories for the Red Sea Escape Route

Scientists from time to time have tried to study whether the parting of the waters, can also be understood through natural processes.

Tsunami

Some have speculated about a tsunami, which would have caused waters to retreat and advance rapidly. Such an event would not have caused the gradual overnight divide of the waters as described in the Bible, nor would it necessarily have been associated with winds.

Wind Setdown & Underwater Reef

Other researchers have focused on a phenomenon known as “wind setdown,” in which a particularly strong and persistent wind can lower water levels in one area while piling up water downwind. Wind setdowns, which are the opposite of storm surges, have been widely documented, including an event in the Nile delta in the 19th century when a powerful wind pushed away about five feet of water and exposed dry land.

A previous computer modeling study into the Red Sea crossing by a pair of Russian researchers, Naum Voltzinger and Alexei Androsov, found that winds blowing from the northwest at minimal hurricane force (74 miles per hour) could, in theory, have exposed an underwater reef near the modern-day Suez Canal. This would have enabled people to walk across.

But according to Drews and Han, the ‘reef scenario’ is unlikely. The reef would have had to be entirely flat for the water to drain off in 12 hours. A more realistic reef with lower and deeper sections would have retained channels that would have been difficult to wade through. In addition, the scientists are skeptical if refugees could have crossed during nearly hurricane-force winds.

The study (published in the online journal PLoS ONE as ‘Dynamics of Wind Setdown at Suez and the Eastern Nile Delta‘) is part of a larger research project by Drews into the impacts of winds on water depths, including the extent to which Pacific Ocean typhoons can drive storm surges.

Volcano Death Recipe: Pompeii Vesuvius Victims Cooked Alive

Skeletons and Casts from human victims at OplontisAn Italian study of the plaster casts of the 79 AD Vesuvius eruption victims showsmost were not suffocated by ash, as is often assumed. Neither were they knocked down by fast-moving currents of hot gas. Rather, the extreme heat was the main cause of the instantaneous deaths at Pompeii. At temperatures up to 300C, the unfortunate citizens, including those seeking shelter inside buildings, were cooked alive.

Italy, 79 AD. Vesuvius erupts, throwing up a high-altitude column from which ash began to fall, blanketing Pompeii and surrounding areas, and creating an invaluable archaeological record,preserved for almost 2,000 years.

It is estimated 10% of the city’s population did not manage to escape in time, and from the city’s well-preserved remains, there is evidence of more than 1,000 casualties recovered so far, many in the form of plaster castsfrom the impressions the victims’ bodies left in the ashes. Some show people lying on their backs or sides in an apparently relaxed posture, but most look as if, for one horrible instant, time stood still.

The eerie, life-like poses of the unfortunate who fell to the volcano’s temper, are a striking reminder of the victims’ individuality, and make it impossible not to wonder how exactly they’ve died.

The heat was enough for sudden and complete vaporization of soft tissues of the victims at Herculaneum and Oplontis, where the flesh was suddenly replaced by the ash, but was insufficient at Pompeii.

How did the Pompeiians die?

Most of Pompeii’s inhabitants who survived the early phase of the eruption, during which buildings collapsed, died by exposure to extreme heat, according to the Italian study. A hot mixture of fine ash and hot gas came flowing down the volcano’s slopes, a raging current which caused numerous fatalities at Pompeii, about 10kms from the volcano’s vent. The researchers found that even at the flow’s termination point, temperatures of over 250C caused instant death. Until now it was believed that many who survived the early eruptive phase were latersuffocated by ash.

The study, authored by Giuseppe Mastrolorenzo, Pierpaolo Petrone, Lucia Pappalardo and Fabio M. Guarino and published in open access journal PloS ONE, used digital models of the pyroclastic surges to compute size, density and velocity, as well as analysing human remains from the Pompeii archaeological site, Herculaneum and Oplontis.

Lava? Try Pyroclastic Flows

The 79 AD Vesuvius eruption caused six major pyroclastic surges and flows, each increasing in power. The three early surges stopped ahead of Pompeii’s north-western walls, while the three later surges passed over the town. Although less powerful than the last two surges (whose reach extended more than 15 km from the vent), and in spite of little material damage and an ash deposit of only 3cm, the fourth pyroclastic surge (S4) caused most of the fatalities at Pompeii.

Numerical simulation of the S4 Pyroclastic Density CloudThe Italian scientists calculated that the S4current reached Pompeii at a velocity of 29m/s (about 104km/h) and was up to 18 metres high. It took the cloud of hot gas and ash less than a minute and a half and maybe as little as 30 seconds to pass through the city.

Heat-shock Forensics

In their search for evidence of S4’s lethal effects, the scientists studied the casts and skeletons’ body postures of some of the 650 victims preserved in the deposits of the S4 surge, hitherto supposed to have died from asphyxiation. For comparison, they also studied 37 corpses discovered at the seaside site of Oplontis and 78 skeletons unearthed at Herculaneum. Impact-like symptoms such as ruptured body parts, are rare, leading the scientists to conclude the S4 flow’s dynamic overpressure was below the human lethal threshold. More surprising was that 73% of the S4 victims examined were found to have a ‘life-like stance’. Death was so sudden, that the victims died mid-movement.

The researchers consider the widespread occurrence of this stance to be key evidence that most of the victims were alive at the time of posture arrest, and that they all were exposed to the same lethal conditions.

They say the sheer number of victims ‘frozen in action’ is indicative of a condition known as ‘cadaveric spasm’. Often associated with violent death, it means an instantaneous rigor occurs, crystallizing the last activity prior to death. Cadaveric spasm commonly involves only groups of muscles. Only exceptionally for example in battle situations, due to exposure to extreme heat would it affect the entire body.

Plaster Casts of Human Victims at PompeiiSeventy-six per cent of the victims showed limb contraction while a ‘pugilistic attitude’ (limb flexures that result from dehydration and shortening of tendons and muscles) was found in 64% of the S4 casualties. Both post-mortem postures are generally observed as secondary effects in victims exposed to extremely high temperatures, and according to the authors, wrongly attributed to attempts at self-defence by previous studies.

Getting the Temperature Just Right

In order to verify their theory of instant death caused by theheat-shock, the researchers heated human bones to above 200C (the human survival threshold) and compared colour and texture modifications to the bones of the S4 victims. The tests suggest that bones from Pompeii were exposed to temperatures between 250 and 300C. The Herculaneum and Oplontis skeletons were exposed to temperatures up to 500 and 600C respectively.

According to the authors, such temperatures would also explain the well-preserved body imprints found at Pompeii: The heat was enough for sudden and complete vaporization of soft tissues of the victims at Herculaneum and Oplontis, where the flesh was suddenly replaced by the ash, but was insufficient at Pompeii. This accounts for the nearly perfect preservation of the entire body imprint (as shown by the plaster casts) in the ash as a consequence of the delayed disappearance of flesh of these bodies.

The estimated 250 to 300C temperature is also consistent with the melting of ancient Roman silverware, but not glass, at Pompeii.

Frozen in Action,Cooked Alive. Doesthat hurt?

Can we fully exclude that the hot ash particles caused suffocation? The researchers argue that, although the concentration of inhalable ash particles approached a lethal level, the S4 cloud passed too quickly to cause asphyxia. The time Pompeii’s citizens were exposed to the ash cloud was too short, suffocation as cause of death would have required a longer exposure time, resulting in several minutes of sheer agony – and loss of muscle tone, inconsistent with the ‘life-like’ postures.

What about the suffering involved with being cooked alive? At Pompeii, a rise of temperature to more than 250C in less than 30 seconds, would have (hopefully) heated the victims brains to a point of unconsciousness within a few seconds, as well as instantly boiled the victims’ nerve endings.

Good thermopalia or not, I don’t think I’ll be movinganywhere near an activevolcano anytime soon.

‘Mastrolorenzo G, Petrone P, Pappalardo L, Guarino FM, 2010 Lethal Thermal Impact at Periphery of Pyroclastic Surges: Evidences at Pompeii’ is available for download from PLoS One under a creative commons attribution license.

World’s Oldest Leather Shoe Discovered in Armenia

armenian shoe cave - oldest leather shoeA 5,500-year-old leather shoe has been found in a cave in Armenia. The shoe 1,000 years older than Giza’s Great Pyramid and 400 years older than Stonehenge is perfectly preserved and was found complete with shoelaces. It is believed to be the oldest example of enclosed leather footwear, out-dating the shoes worn by Otzi the Iceman by a few hundred years.

The shoe is sole-less, made out of a single piece of cow hide and was shaped to the wearer’s right foot. It contained grass, which might have served to either keep the foot warm or to maintain the shape of the shoe. It is not known whether the shoe 24.5cm long and a European size 37 belonged to a man or a woman, though it would have been ideal for a male of that era.

The shoe is similar to the ‘pampootsies’ worn until the 1950s on Irelands Aran Islands. In fact, enormous similarities exist between manufacturing technique and style of this shoe and those found across Europe at later periods, suggesting that this type of shoe was worn for thousands of years across a large and environmentally diverse geographic region, said Dr Ron Pinhasi of Cork University.

We couldn’t believe the discovery. The crusts had sealed the artefacts and archaeological deposits and artefacts remained fresh dried, just like they were put in a can.

Such a well-preserved artifact from a Middle Eastern archaeological site is considered an amazing find because organic materials usually deteriorate due to the high content of salts and fungi in the soil, as well as fluctuations in temperature and humidity.

The discovery was made in Vayotz Dzor province on Armenias border with Iran and Turkey by Diana Zardaryan of Armenias Institute of Archaeology. I was amazed to find that even the shoelaces were preserved, she said.

The stable, cool and dry conditions in the Areni-1cave resulted in the exceptional preservation of the shoe and other objects. Other finds included large containers, many of which held well-preserved wheat, barley, apricots and other edible foodstuffs.

Click the images to see them inlarge size

A thick layer of sheep dung covered the floor of the cave, sealing the artefacts and archaeological deposits and further assisting preservation. Other discoveries included a broken pot, fishbones and sheep’s horns.

We couldn’t believe the discovery, said the dig’s co-director Gregory Areshian, part of an international team of archaeologists working at the site. The crusts had sealed the artefacts and archaeological deposits and artefacts remained fresh dried, just like they were put in a can.

Both the shoe and the grass samples were shown to be the same age, and dated to the Chalcolithic period, about 3500BC.

While the Armenian discovery is believed to be the oldest recorded example of a leather shoe and the oldest Eurasian shoe it is not the oldest known footwear. Predating the shoe by as many as 2,000 years are a moccasin made of plant material and a pair of leather sandals discovered in the 1970s in a cave in Missouri.

Leather sandals of a similar age to the Areni-1 shoe were found in a cave in Israels Judean Desert but these were never directly dated. Rather, their age is based on various other associated artefacts found in the Cave of the Warriors.

The archaeologists have not yet identified the purpose of the cave.”We know that there are children’s graves at the back of the cave but so little is known about this period that we cannot say with any certainty why all these different objects were found together,” said Dr Pinhasi.The international team will continue to excavate the many chambers of the cave.

The same team last year announced the find ofthe ‘world’s oldest human brain’ at the Areni-1 site, a 9 by 7 centimetres brain fragment, possible evidence of ceremonial cannibalism as well as a large number of vessels and grapevine shoots (possibly the ‘world’s oldest commercial winery’).

Further details on the study of the Areni-1shoeare published in the online scientific journal PloS ONE as First Direct Evidence of Chalcolithic Footwear from the Near Eastern Highlands.