Note: this topic is from 4/04/2007. Thanks Valin.
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Posted on 04/04/2007 5:54:02 AM PDT by Valin
Around 250 million years ago, a huge volcanic eruption triggered a deadly series of events that wiped out 95% of all species on Earth. Scientists have been piecing together the story of what happened.
Our planet has a troubled and turbulent past: five catastrophic natural events have caused mass extinctions of life on Earth. Perhaps the most famous one is the asteroid impact that caused the demise of the dinosaurs. But the most extensive extinction event occurred even before dinosaurs were around. In the Permian era, about 250 million years ago, a destructive volcanic eruption radically altered conditions on Earth and scientists are still piecing together evidence in an attempt to understand its devastating impact.
Clues in the earth Paleontologist Roger Smith from the Museum of South Africa has been searching for hints about the extinction in the Karoo basin in South Africa. Today, it’s hard to imagine life ever thrived in this barren, inhospitable landscape where living things struggle to survive. But by examining rock strata in the area, layers of rock that have built up over time, he has built up an impression of what existed here in the past.
Smith has been studying a layer of blue-green mud-rock laid down 300 million years ago. Analysis of the layer has revealed that it is made up of sediments deposited by frequent floods. “These blue-green mud rocks of the Permian represent lush wet flood plains. Lots of life, lots of flourishing vegetation, and many types of mammal-like reptiles,” explains Smith. Above the lush mud-rock layer sits rock that Smith describes as the “death zone” since it is completely devoid of life. The rocks contain no evidence of animal life, let alone plants or even soil.
For over 150 years, the reason for the lifeless conditions in the Karoo basin has been a mystery. But in the early 1990s, some researchers stumbled on an exciting clue thousands of miles away in Siberia.
Volcanic evidence Beneath the frozen Siberian landscape, thousands of square miles of lava were discovered. Known as the Siberian traps, these testify to the biggest and most destructive volcanic eruption the Earth has ever experienced.
The scale of the flood basalt is difficult to grasp. Two hundred and fifty thousand cubic miles of lava were spewed out over almost a million years. According to UCL’s disaster scientist Bill McGuire, it would have been ‘hell on Earth’. “You would have had huge fractures slashing the crust open, and very fluid lava more than 1000 degrees [C or F?] in temperature, fountaining out and pouring off in all directions. Any life around there would be burnt,” he says.
Widespread consequences But how did the Siberian traps affect life in the Karoo basin, on the other side of the world? The lava was certainly deadly, but scientists believe that the far-reaching effects of the Siberian traps lie in their ability to alter the Earth’s climate.
To understand the impact of this ancient flood basalt, it’s helpful to look at a more recent example: the Laki eruption of 1783. In this year, a 20-mile-long fissure spilled lava over 200 square miles of Iceland for a period of 8 months. Although no one actually died as a direct result of the lava flow, the flood basalt caused widespread destruction over the whole of Europe.
Along with red-hot lava, the Laki eruption spewed out 122 million tons of sulphur compounds. These combined with water vapour in the stratosphere to form tiny droplet clouds of sulphur dioxide. Acting like mirrors, the light-coloured droplets reflected sunlight back into space. Deprived of the sun’s heat and light, the entire northern hemisphere cooled. Temperatures dropped to 7ºC below the average in Iceland and in the western United States they dropped by 5ºC. The sulphur dioxide eventually fell to the Earth as acid rain which poisoned the struggling crops and eroded the soil. As a result, 50% of Iceland’s cattle perished and 20% of its population starved.
The Siberian traps were 250,000 times bigger than Laki. “The Laki eruption actually covered a relatively small area, about a third the size of greater London. If we look at the Siberian flood basalts they covered a huge area. The deposits cover an area almost the size of the whole central part of Russia, something like the size of the United States,” says McGuire.
Imagine the effects of Laki amplified two-and-a-half million times. The deadly belch of the Laki traps lasted for 8 months, but 250 million years ago, the massive slashes in the Earth’s crust let out their noxious gases for hundreds of thousands of years. The Siberian traps are the likely culprit for the extreme global climate change behind the mass extinction. A huge sulphuric sun-block brought darkness and savage cold. Many species perished from the sudden glaciation. Voracious acid rain gnawed vegetation for centuries on end.
Yet the late Permian era suffered a second affliction. Over thousands of years, greenhouse gases belched out by the traps accumulated in deadly quantities. Carbon dioxide, water vapor and methane shrouded the earth, trapping heat. It is estimated that levels of carbon dioxide were up to six times higher than today. All this translates to a 10ºC temperature rise in the Karoo basin.
Its effect can be read in the Karoo rock strata. Above the blues, grays and greens of the floodplain mud sits a layer of fiery red rock. This represents the moment that iron minerals in the mud and soil oxidized as they became exposed to the air. It marks the time that the lush oasis became the parched, dead land that we see today.
Effects in the oceans
The oceans also suffered. Geologist Paul Wignall from the University of Leeds in the UK examined the marine fossil record in Iceland from the Permian era. He found that the number of fossils gradually diminished, until there were none at all. At this point, Wignall analysed the rock and found that it contained many pyrite crystals. He points out that pyrite, also known as fools’ gold, cannot form in the presence of oxygen.
If pyrite was forming in the ocean, there couldn’t have been much oxygen. Normally, the deep ocean gets its oxygen from the poles: cold water absorbs oxygen from the atmosphere. This cold, dense, oxygenated water then sinks and moves along the sea floor towards the equator.
Two hundred and fifty million years ago, the oceans, like the land, heated up. Wignall has calculated that around the equator, temperatures would have approached 38 C, about the temperature of bath water. Near the poles, temperatures were more akin to what we experience in California today.
With no cold water at the poles, the oceans’ circulation system shut down. Life in the oceans began to die. Without oxygen, organic debris can’t decompose properly, and the bacteria that breaks down this dead matter produces toxic hydrogen sulphide. Today, this deadly, rotten-egg smelling gas is found in low oxygen environments like bogs and swamps. Back then, it devastated the oceans, making them stinking and poisonous.
These putrid oceans released vast amounts of hydrogen sulphide into the atmosphere, marking the final death toll for the few remaining species on land already battling drought and famine. A measly 5% of species escaped obliteration.
It took around 6 million years for biodiversity to return to normal. Today, it’s been 65 million years since the last major extinction event. Life is thriving, and it’s easy for us to forget that the world around us has been fundamentally shaped by colossal natural disasters. Our existence is more fragile than we imagine. Huge flood basalts, asteroid impacts, gamma ray bursts… they do happen. And they will happen again.
National Geographic Magazine - When Life Nearly Came to an End - The Permian Extinction http://www.nationalgeographic.com/ngm/0009/feature4/
BBC - The Day theh Earth Nearly Died http://www.bbc.co.uk/science/horizon/2002/dayearthdied.shtml
Tag you’re it!
Bush’s fault.
Basalt credits for sale. Get your basalt credits here.
It had to be said.
Have no fear our long national nightmare will be over on 1/20/09.
So much for that idiot Algore and his climate change minions. Gee when all is said and done we can’t change what is meant to be. Imagine that!
AlGore, you are an ignorant fool...............
WE ARE ALL GOING TO DIE
Eventually, yes, we will.
That would have to be C, as quartz conversion is only beginning at 1000 degrees F. But even 1000 degrees C is only 1832 F, and I think at best you have some kind of mushy, yogurt-consistency lava at that point. Somebody please double check my figures.
“That would have to be C, as quartz conversion is only beginning at 1000 degrees F. But even 1000 degrees C is only 1832 F, and I think at best you have some kind of mushy, yogurt-consistency lava at that point. Somebody please double check my figures.”
I checked your figures and I found that this would be hot.
Correction.... that should be “very” hot........sorry
My wife is a ceramic artist, so we typically work with temperatures in the 1900 degrees F to 2500 degrees F range.
Trust me: It’s hot.
Note: this topic is from 4/04/2007. Thanks Valin.
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And how do we know that one or more large boloids did not crash into Siberia and start this infernal mess?
The infernal mess accumulated over millions of years and had nothing to do with the Permian mass extinction, but I wanted to add this old topic to the catalog for the sake of completeness. :’)
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