What Causes Mass Extinctions?

They are known ominously as the Big Five—the five greatest mass extinctions over the past 500 million years, each of which is thought to have annihilated anywhere from 50 to 95 percent of all species on the planet.

Many unsolved mysteries remain regarding these disasters, perhaps the greatest of which is what caused each of them. But research is uncovering how these extinction events dictated the fate of life on this planet—for instance, determining which animals first crawled onto land and which ruled the oceans.

    * The K-T extinction

The most recent of the Big Five is the most familiar one—the cataclysm that ended the Age of Dinosaurs. The end-Cretaceous or Cretaceous-Tertiary extinction event, otherwise known as K-T, killed off all dinosaurs save birds roughly 65 million years ago, as well as roughly half of all species on the planet, including pterosaurs.

Not only did mammals sweep across the planet after K-T, but sharks expanded across the seas, explained American Museum of Natural History vertebrate paleontologist Jack Conrad.

"Throughout the Age of Dinosaurs, you always had these large reptile carnivores dominating the water, such as ichthyosaurs, mosasaurs and plesiosaurs," Conrad explained. "Only after they die do you see big sharks becoming really prevalent. You probably wouldn't have seen orcas or blue whales either had reptile dominance of the seas not gone by the wayside."

Although research suggests the planet was on the verge of environmental upheaval before the K-T extinction event, the straw that broke the dinosaur's back is widely thought to have been an impact with an asteroid or comet. Still, a number of researchers contend evidence commonly linked with such an impact, such as the metal iridium, which is rare on the Earth's crust, could also be caused by the massive volcanic eruptions at the Deccan Flats in India, another popular contender for the dinosaur-killing catastrophe.

    * The Triassic-Jurassic extinction

The end-Triassic, or Triassic-Jurassic extinction event about 200 million years ago is thought by many to possibly have set dinosaurs on the path to their 135-million-year domination of much of life on Earth. It also ended life for roughly half of all species.

Until this disaster, mammal-like creatures known as therapsids were actually more numerous than the ancestors of the dinosaurs, known as archosaurs.

"The dinosaurs definitely survived better than the early proto-mammals did, and the extinction event might have entirely tipped it in their favor," said Rutgers University paleobiologist George McGhee.

Of the Big Five, the Triassic-Jurassic extinction has the fewest number of scientists currently researching it, "although that's changing right now," said Columbia University paleoecologist Paul Olsen. Its cause remains under great debate, with the best contender so far being the massive volcanic eruptions at the "Central Atlantic magmatic province," a region that encompassed a staggering 4.2 million square miles (11 million square kilometers), an area larger than Canada. Another main possibility could be an astronomical impact, Olsen said, although as with the K-T event, the evidence for both types of catastrophe can get maddeningly blurry.

    * The Permian-Triassic extinction

The largest of the Big Five was the end-Permian or Permian-Triassic extinction event roughly 250 million years ago, which eliminated as much as 95 percent of the planet's species.

Before this extinction, marine animals were mostly filter feeders stuck in place on the seafloor, such as crinoids or "sea lilies." Afterward, the seas became far more complex with mobile creatures such as snails, urchins and crabs.

The most likely final trigger for the end-Permian was again massive volcanism, this time at the Siberian Traps, which spewed as much as 2.7 million square miles (7 million square kilometers) of lava out, an area nearly as large as Australia.

Recent evidence suggests, however, that the end-Permian may have been long in the making.

    * The late Devonian extinctions

The late Devonian extinction events were actually two sharp pulses of death about 360 million years ago, each just 100,000 to 300,000 years apart.

Each pulse was accompanied by a massive drop in temperature, with the steaming seas of the Devonian—surface temperatures of which were about 93 degrees F (34 degrees C)—dropping to about 78 degrees F (26 degrees C), "and marine organisms would not have liked that at all," McGhee said. As to what caused these cold snaps, the ever-popular suspects are ash and dust kicked up by either astronomical impacts or massive volcanism.

At that time, plants had made it onto land, as had spiders, scorpions and similar creatures. Right before the extinction events, the first proto-amphibians made it onto shore. However, the invasion of the so-called elpistostegalians—distant relatives of the coelacanth—"got wiped out by these extinction events," McGhee explained. "It wasn't until at least another 10 million years later that we got footprints from vertebrates on land again, this time from the ichthyostegalians, the proto-amphibians we're all descended from. Who knows how the world might have been different."

    * The Ordovician-Silurian extinctions

The earliest of the Big Five, the end-Ordovician or Ordovician-Silurian extinction events some 444 million years ago, are reckoned by many to be the second largest.

These also consisted of a pair of die-offs, apparently involving massive glaciation and a resulting fall in sea levels. The cause of this glaciation remains a mystery, but one idea was that land plants actually caused it, pulling so much carbon dioxide out of the atmosphere that global cooling resulted, McGhee explained.

Curiously, even though the end-Ordovician led to a huge loss of life, in a way it actually had very little impact on the persistence of lineages. Although the four other Big Five extinction events led to huge changes in which animals rose to prominence, the same animals that dominated before the end-Ordovician dominated afterward.

Otherwise, "one neat thing about mass extinction events is that they're often reset buttons, where you change what dominates the globe," Conrad said. "You open the door to things like us to live."

ATLANTIS - The Lost Empire

Atlantis is one of the world's greatest mysteries. To many, its very name evokes a mystical sense of familiarity and lost memories. It is said to be the lost Atlantic continent, the first home of civilisation, an earthly paradise, struck down by a natural catastrophe at the height of its power, and now lying deep under the ocean, with only the tops of its mountains protruding from the ocean floor.

To others, Atlantis is merely a legend, invented by Plato, the Greek philosopher, as a backdrop for two of his dialogues: Timaeus and Critias.

Another belief is that Atlantis was a true precursor of the early civilisations and not located in the Atlantic at all, but instead occupying some other location, like the Greek islands of Crete or Santorini, as opposed to the Azores, Madeira, or the Canary Islands.

The name Atlantis derives from atlas, the giant Greek God who is said to have supported the sky. In Greek, Atlantis means "Daughter of Atlas".

PILLARS OF HERCULES

One popular assertion from Plato is that Atlantis was ‘beyond the Pillars of Hercules’. These are almost unanimously thought to be the outcrops either side of the Strait of Gibraltar.
The mythology of the Straits of Glbraltar is neat and explanatory. Geographically speaking, they represent a narrow stretch of water separating the Mediterranean Sea from the Atlantic Ocean. And mystically, they separate the known world from the unknown.
To the north and south of the Straits are two large promontories - the Rock of Gibraltar in Europe and the Abyla on the African coast. These are the pillars separating the narrow strait. But according to legend the two promontories were much closer. Indeed, they were a closed gate. Until, that is, the mighty Hercules stood by the rocks and pushed them apart, thus allowing the waters to flood in.

ATLANTIS AND COLONISATION

The ancient Greeks were great colonisers, founding many Mediterranean cities which exist to this day. And bearing this adventurousness in mind, we can see the myth of Hercules separating the straits as a desire of the ancient Greeks to learn more, shedding light on what is dark; a noble pursuit that was later to find additional expression in their great philosophers, of which Plato was one of the greatest exponents. In this sense, Atlantis can, therefore, be seen in a place where our knowledge is ‘dark’, rather than physically beyond.
And it is, perhaps, in the same magnificent spirit that Atlantis rose to popular consciousness in the 19th century, during a similar time of great expansion and colonisation. This was the time of the great European empire building, and the time when America first expressed its wish to be a superpower, going on to eclipse Europe.
We can here see why some people would be eager to realise the existence of a great lost civilisation, divorced from all the other races on Earth. And to this we must also add the publication, in 1859, of Charles Darwins ‘Origin of Species’. With God in decline, a new theory of human origins was abroad - that we had evolved through natural selection, and western society was its higherst expression.
Such an idea infused Victorian society in the 19th century. With the Industrial Revolution well advanced and the European empires coming very much into being, the Victorians saw themselves as the apex of the evolutionary story. And with such sentiments, it is not difficult to see the inspiration for the literal profusion of ideas concerning Atlantis. The American and the western European was retracing the greatness that existed in the deep, dark past?

IGNATIUS DONNELLY

Due to this popular awareness, when Ignatius Donnelly published his ‘Atlantis: The Antediluvian World’ in 1882, it created immense interest. Donnelly, an American Congressman, created many of the controversies and views concerning Atlantis that survive to this day. Principle among these was his idea that at one time Atlantis existed in the middle of the Atlantic Ocean, until its destruction in a cataclysm.
Positing an earthquake as the most likely reason for its destruction, to Donnelly, Atlantis had acted as a form of bridge between cultures either side of the Atlantic, the island itself being the primary source of those cultures.
Donnelly found evidence for this idea wherever he looked. For instance, throughout the Atlantic there are small islands which are, infact, the tips of undersea mountains. To Donnelly these are all that is left of the mountains that used to be above sea level, forming part of the Atlantis homeland.
Similarly, evidence of his idea of Atlantis as the primary source of culture could be seen throughout the ancient world, in the similarities of cultures, architecture, writing skills and other achievements from the Incas to the ancient Egyptians. He also posited the idea that the sudden appearance of these cultures could only be explained by the sudden disappearance of their mother culture.

PSEUDO-SCHOLARS

Ignatius Donnelly was one of the first modern pseudo-scholars. Mocked and derided by most serious researchers, they are often believeable and always popular. In Donnelly’s case, his persuasive writing went on to prompt British Prime Minister Gladstone to attempt to get Parliament to fund a ship to trace the sunken coastline of Atlantis.
Today, we know that much of Donnelly’s evidence was untrue. But this should not be used as an excuse to ignore pseudoscholarship in its entirely.
For instance, the list of great pseudo-scholars of the past include Charles Darwin (a lifelong amateur), Gregor Mendel (the discoverer of genetics and a monk), and the great Sir Isaac Newton himself; his real search was not so much scientific, but to find the ‘great spirit of the universe’.
Of course, not all pseudoscholars are as successful as this trio. Indeed, many of them do write absolute hogwash. You may even decide that I fit this last category. But at worst, such writers at least fuel the experts to define more completely, and at best, they can begin entirely new sciences.

LEWIS SPENCE

Donnelly began an Atlantian tradition of speculation, deep theory and occasional lunacy, which continues to this day.
One principal writer in this vein was Scottish newspaper editor and editor of ‘The Atlantis Quarterly’, Lewis Spence. After writing studies of the mythologies of Egypt, Babylon and the early Americas, in the 1920s he turned his attention to Atlantis, which he decided had covered most of the Atlantic Ocean in the Miocene period, ending ten million years ago. At this point it disintegrated into smaller islands and, from 25,000 to 10,000 years ago, disappeared completely.
Studying the Atlantic coast of Europe, Spence decided that the early humans such as Cro-Magnon Man had actually migrated from the western side of Atlantis, near the Americas. Only in this way can we see Cro-Magnon Man as the real invader he was, going on to wipe out Europe’s indigenous Neanderthal Man.
Taking his evidence from a wide variety of sources, including archeology, anthropology, geology and mythology, much of this is totally discredited, but this did not stop the speculation, sometimes coming from scientists themselves.

THE AZORES, STUPID

One such scientist was Austrian physicist Otto Muck. Opting for the Azores as the location of the destroyed Atlantis, he argued that in 8500BC the sunken continent was lost when a large asteroid struck the Charleston coast of North America.
Some most unusual evidence of something strange about the Azores did, infact, surface in 1898, when a telegraph company used grappling equipment to mend a broken Transatlantic cable 500 miles north of the Azores.
French geologist Pierce Termier was sent samples from rocks brought up from the sea bed. Identifying them as basaltic lava, they did however show evidence of volcanic activity ABOVE sea level in the recent geological past.
No real evidence has been found to link an asteroid collision to the destruction of a large Atlantic island, but this has not stopped some amazing disaster scenarios to irritate scientists.

DISASTER SCENARIOS

Typical was Austrian engineer Hans Hoerbiger. Fascinated, by astronomy and mythology, he put mythologies of a malevolent Moon down to the fact that Earth had been struck by the Moon in the past.
However, this was not our present Moon. This, Hoerbiger, was convinced, was just a ball of ice. But in the past, Earth had had a second Moon, a captured comet, which caused a great flood and other disasters when it exploded.
Many Atlantis theorists have associated this much discredited disaster scenario with the destruction of Atlantis. And the same can be said for the ideas of psychoanalyst, Emmanuel Velikovsky.
Fascinated by Sigmund Freud’s idea that Moses was also the Egyptian pharaoh Akhnaton (a pharaoh who briefly introduced into Egypt the idea of a single God), Velikovsky became intrigued by early mythologies.
In particular, the disasters such as the Flood arrested his attention. In 1680 a comet had approached Earth, and the scientist W Whiston had put forward the idea that on a previous encounter this comet had caused the Biblical Flood.
Velikovsky tended to agree with this idea, and went on to formulate a cosmology in which a comet had several times approached Earth, causing all Biblical disasters, and accounting for the destruction of Atlantis, before finally settling down to become the planet Venus.

IN CONCLUSION

Of course, none of these ideas can now be backed up by real science. For instance, the Moon is not made of ice, Venus is a definite planet. But in the world of Atlantian speculation, anything goes.
But my central point here would be, and why not? For instance, academia must always be challenged, otherwise all we will ever have for knowledge is consensus, and consensus can cripple knowledge.
Similarly, archaeology has made many advances in their techniques due to their need to disprove certain pseudoscholars. So if for no other reason than this, pseudoscholarship, and Atlantology in particular, has a valid role.
But most importantly, Atlantis makes us expand our minds - gives us the idea that knowledge is not complete. It keeps alive the thirst to inquire - an inquiry that led to the ideas and ideals of the modern world in the first place.
Whether theory or fantasy, Atlantis remains one of the central symbols of the thinking mind.

I do hope you have enjoyed reading this article, as much as I have enjoyed writing it.

Perhaps you have your own theories on the whereabouts of Atlantis that you may like to share and discuss.

I look forward to hearing from you.

THE GREAT FIRE OF ROME

Could a ruler, even one as eccentric as the Roman emperor Nero, set fire to his own capital? The disastrous blaze that devastated the city of Rome in 64 BC has never been satisfactorily explained....

Though the infamous emperor Nero ruled Rome for less than two decades, his reign witnessed tremendous changes to the empire's capital city. Lucius Domitius Ahenobarbus -- more often known as Nero -- was a great-grandson of Caesar Augustus.

The Great Fire of Rome erupted on the night of July 18 to July 19, 64. The fire started at the southeastern end of the Circus Maximus,Rome's mammoth chariot stadium. in shops selling flammable goods.

In a city of two million, there was nothing unusual about such a fire -- the sweltering summer heat kindled conflagrations around Rome on a regular basis, particularly in the slums that covered much of the city. Yet this was no ordinary fire. The flames raged for six days before coming under control; then the fire reignited and burned for another three.

When the smoke cleared, 10 of Rome's 14 districts were in ruin. The 800-year-old Temple of Jupiter Stator and the Atrium Vestae, the hearth of the Vestal Virgins, were gone. Two thirds of Rome had been destroyed.

According to Tacitus { aristocrat and historian } , upon hearing news of the fire, Nero rushed back to Rome to organize a relief effort, which he paid for from his own funds.

After the fire, Nero opened his palaces to provide shelter for the homeless, and arranged for food supplies to be delivered in order to prevent starvation among the survivors.In the wake of the fire, he made a new urban development plan. Houses after the fire were spaced out, built in brick, and faced by porticos on wide roads.

Nero also built a new palace complex known as the Domus Aurea in an area cleared by the fire. This was a 300 acre palatial complex that featured the Colossus Neronis, a 37-meter-high bronze statue of Nero placed just outside of the entrance. To find the necessary funds for the reconstruction, tributes were imposed on the provinces of the empire.

HISTORICAL VIEWS

The varying historical accounts of the fire come from three secondary sources- Cassius Dio, Suetonius and Tacitus. The primary accounts, which possibly included histories written by Fabius Rusticus, Cluvius Rufus and Pliny the Elder, did not survive.

These primary accounts are described as contradictory and gross exaggerations.At least four separate stories circulated regarding Nero and fire:

Cassius Dio:

Motivated by a desire to destroy the city, Nero secretly sent out men pretending to be drunk to set fire to the city. Nero watched from his palace on the Palatine Hill singing and playing the lyre.

Suetonius:

Motivated by an insane whim, Nero quite openly sent out men to set fire to the city. Nero watched from the Tower of Maecenas on the Esquiline Hill singing and playing the lyre.

Tacitus 1:

Nero sent out men to set fire to the city. Nero sang and played his lyre from a private stage.

Tacitus 2:

The fire was an accident. Nero was in Antium.

Tacitus was a member of this Roman elite, and whether there is a bias in his writing is difficult to know. Indeed, Tacitus was still a boy of 9 at the time of the fire, and he would have been a young teenager in 68 A.D., when Nero died.

WAS NERO THE ARSONIST ??

NERO has always been labelled as a tyrant and an eccentric, and the long list of his evil deeds , as the murder of his wife and mother, certainly gave grounds for suspicion.

Rumours are that one of the grandest plans of Nero was to tear down a third of Rome so that he could build an elaborate series of palaces that would be known as Neropolis. The senate, however, objected ardently to this proposal.

The emperor's passion for theatre fed rumours that he wanted an opportunity to sing a poem of about the burning of Troy.

IDEAL SUSPECTS

It was an easy matter to blame the CHRISTIANS for the blaze.Small in number and poor, they were considered as foreigners by the citizens of Rome. The fire gave Nero the perfect opportunity to begin a systemic persecution of the christians in the hope that he could placate the anger of the people and turn opinion in his favour.

Countless arrests were made and many met gruesome deaths- fed to lions during gladiator matches, crucified and used as human torches...

Yet there is evidence that, in 64 A.D., many Roman Christians believed in prophecies predicting that Rome would soon be destroyed by fire. Perhaps the fire was set off by someone hoping to make the prediction come true.

Today, 20 centuries later, the mystery remains!