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TOPIC: The 'Great Dying'
Blobrana


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Permian-Triassic mass extinction
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Did Magnetic Blip Trigger Mass Extinction?
It was a dying on a scale never seen before or since on Earth. The slaughter was everywhere; the fertile ocean and balmy supercontinent Pangea were transformed into killing fields, littered with the bodies of ancient animals. By the time the dust had settled on the Permian-Triassic mass extinction 250 million years ago, 90 percent of life on the planet had been snuffed out.

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Blobrana


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RE: The 'Great Dying'
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The greatest mass extinction in Earths history also may have been one of the slowest, according to a study that casts further doubt on the extinction-by-meteor theory.
Creeping environmental stress fuelled by volcanic eruptions and global warming was the likely cause of the Great Dying 250 million years ago, said USC doctoral student Catherine Powers.

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Blobrana


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It was the biggest mass extinction in Earth's history: a climate catastrophe about 252 million years ago that wiped out more than 95 per cent of all plant and animal species on the planet.
But scientists have theorised that somewhere in that oxygen-starved world, where a "runaway" greenhouse-gas disaster nearly stopped the evolution of life dead in its tracks, a few communities of primitive organisms - including our own pre-mammal ancestors - must have found a handful of habitable ecological niches in which to survive and wait out the primordial holocaust.
Now, three Canadian researchers believe they've discovered just such a refuge - the first ever found - in a thin band of rock in B.C., Alberta and Arctic Canada that once formed the coastline of the ancient supercontinent Pangaea.

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Blobrana


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lystrosaurs
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First there was the Permian era; then came the Triassic period. Now palaeontologists have discovered an intriguing interlude, the porcine age, when pig-like creatures ruled the earth.
The animals, known as lystrosaurs, were among the only survivors of the greatest mass extinction event the world has seen, when, around 251m years ago, 95 per cent of all living species were wiped out by a series of volcanic eruptions.
The eruptions eliminated every large predator, so for a million years or more the lystrosaurs had the planet and all its succulent plant life almost entirely to themselves.

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Blobrana


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Permian-Triassic Mass Extinction
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It was the greatest mass murder of all time - poison everywhere, billions slain - but the killer or killers have never been positively identified.
An estimated 95 percent of all marine species and up to 85 percent of land creatures perished, according to Peter Ward, a paleobiologist at the University of Washington in Seattle.
Scientists call it "The Great Dying." Life took millions of years to recover.
Scientific sleuths, however, now think they're making progress toward pinning down what caused the extinction of most plants and animals on Earth some 251 million years ago.

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Blobrana


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RE: The 'Great Dying'
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Today it is common knowledge that the dinosaurs were wiped out by a meteorite impact sixty-five million years ago, which killed half of all species then living.
Far less well-known is a much bigger catastrophe the greatest mass extinction of all time which occurred 251 million years ago, at the end of the Permian period. In this cataclysm, at least ninety per cent of life was destroyed, both on land, including sabre-toothed reptiles and their rhinoceros-sized prey, and in the sea.

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Blobrana


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Title: Methane Release from Igneous Intrusion of Coal during Late Permian Extinction Events
Authors: Gregory J. Retallack and A. Hope Jahren

Unusually large and locally variable carbon isotope excursions coincident with mass extinctions at the end of the Permian Period (253 Ma) and Guadalupian Epoch (260 Ma) can be attributed to methane outbursts to the atmosphere. Methane has isotopic values (13C) low enough to reduce to feasible amounts the carbon required for isotopic mass balance. The duration of the carbon isotopic excursions and inferred methane releases are here constrained to <10,000 yr by counting annual varves in lake deposits and by estimating peat accumulation rates. On paleogeographic maps, the most marked carbon isotope excursions form linear arrays back to plausible methane sources: end - Permian Siberian Traps and Longwood-Bluff intrusions of New Zealand and end-Guadalupian Emeishan Traps of China. Intrusion of coal seams by feeder dikes to flood basalts could create successive thermogenic methane outbursts of the observed timing and magnitude, but these are unreasonably short times for replenishment of marine or permafrost sources of methane. Methane released by fracturing and heating of coal during intrusion of large igneous provinces may have been a planetary hazard comparable with bolide impact.

Addition of the end-Guadalupian case to the better known end-Permian, end-Triassic, and end-Cretaceous cases makes coincidence less likely, and copious generation of methane by intrusion of coals supplies ample killing power. Like meteorite and comet impacts, thermogenic methane outbursts may have been significant hazards to life on Earth.

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Blobrana


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Toxic deep-ocean water triggered "great dying"
 The finger of blame for the greatest mass die-off in Earth history points to a slow, drawn-out demise that came from below, a new study shows.
Researchers discovered that bryozoansa common type of colonial marine creature also known as "moss animals"began slowly declining in oceans across the world many millions of years before the mass-extinction event at the end of the Permian period about 251 million years ago. This so-called Great Dying event wiped out about 90 percent of marine species and 70 percent of land species.

"It was a very gradual process" - Catherine Powers, a palaeobiologist from the University of Southern California who co-authored a study on the new finding.

The first to go were the deeper-dwelling animals, followed by the shallow-water inhabitants.

"It indicates that something from the deep ocean is coming up. Whatever killed these organisms and probably led to this mass extinction is tied to ocean circulation processes" - Catherine Powers.

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Blobrana


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Before the worst mass extinction of life in Earths history 252 million years ago ocean life was diverse and clam-like organisms called brachiopods dominated. After the calamity, when little else existed, a different kind of clam-like organism, called a bivalve, took over.

What can the separate fates of these two invertebrates tell scientists about surviving an extinction event?

A lot, says UWM paleoecologist Margaret Fraiser. Her research into this particular issue not only answers the question; it also supports a relatively new theory for the cause of the massive extinctions that occurred as the Permian period ended and the Triassic period began: toxic oceans created by too much atmospheric carbon dioxide (CO2).
The theory is important because it could help scientists predict what would happen in the oceans during a modern CO2 event. And it could give them an idea of what recovery time would be.

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Blobrana


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Permo-Triassic mass extinction
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Scientists studying mollusc fossils reveal their rise to prominence some 250 million years ago suggests the most devastating mass extinction in Earth's history took a long time as opposed to the result of a catastrophic extraterrestrial cause such as an asteroid strike.
The largest die-off in Earth's history was not the cataclysm that ended the Age of the Dinosaurs some 65 million years ago. Instead, it was the so-called end-Permian mass extinction, which eliminated as much as 95 percent of the planet's species before even the earliest dinosaurs strode the planet.
One alleged consequence of this mass extinction was the dominance of oysters, snails and other molluscs all over the world some 8 million years before the end-Permian

"Our results aren't really consistent with a more catastrophic extraterrestrial cause, such as an asteroid impact although they don't directly contradict the impact theory either" - researcher Matthew Clapham at Queen's University in Kingston, Canada.

Instead, these findings support theories suggesting the end-Permian was triggered by ocean changes long in the making, "the climax of a prolonged environmental crisis".
The whole Permian period, from about 300 million to 250 million years ago, saw gradual warming. This would have slowed down circulation in the ocean, eventually leading to very low levels of oxygen in the water. Massive volcanism near the end of the Permian might have caused more damage to the environment.

"Molluscs are better adapted to such stressful and changing environments, and so could have thrived. The abundance of molluscs we see are symptoms of the conditions that ultimately caused the extinction" - Matthew Clapham.

The research involved gleaning more than 33,000 Permian fossils from blocks of limestone that researchers gathered from China, Greece, Thailand, Nevada and Texas over the course of four years. These blocks were then dunked in vats of hydrochloric acid. Although the acid dissolved the limestone, over millions of years the building blocks of the fossil shells were replaced one by one with silica. This silica resisted the acid and helped the fossils survive.

Source: Xinhua

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