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The Mystery of Mass Extinctions Is No Longer Murky
June 18, 2008If you are curious about Earth's periodic mass extinction events such as the sudden demise of the dinosaurs 65 million years ago, you might consider crashing asteroids and sky-darkening super volcanoes as culprits.
But a new study, published June 15, 2008, in the journal Nature, suggests that it is the ocean, and in particular the epic ebbs and flows of sea level and sediment over the course of geologic time, that is the primary cause of the world's periodic mass extinctions over the past 500 million years.
"The expansions and contractions of those environments have pretty profound effects on life on Earth," says Shanan Peters, a University of Wisconsin-Madison assistant professor of geology and geophysics and the author of the new Nature report. In short, according to Peters, changes in ocean environments related to sea level exert a driving influence on rates of extinction, which animals and plants survive or vanish, and generally determine the composition of life in the oceans.
Since the advent of life on Earth 3.5 billion years ago, scientists think there may have been as many as 23 mass extinction events, many involving simple forms of life such as single-celled microorganisms. Over the past 540 million years, there have been five well-documented mass extinctions, primarily of marine plants and animals, with as many as 75-95 percent of species lost. For the most part, scientists have been unable to pin down the causes of such dramatic events. In the case of the demise of the dinosaurs, scientists have a smoking gun, an impact crater that suggests dinosaurs were wiped out as the result of a large asteroid crashing into the planet. But the causes of other mass extinction events have been murky, at best.
"No matter what the ultimate driving extinction mechanisms might be at any one time, Professor Peters brings the repeated and resultant extinction on oceanic shelves front and forward where it belongs," says National Science Foundation (NSF) Program Manager Rich Lane. "This breakthrough speaks loudly to the future impending modern shelf extinction due to climate change on Earth."
Paleontologists have been chipping away at the causes of mass extinctions for almost 60 years, according to Peters, whose work was supported by NSF. "Impacts, for the most part, aren't associated with most extinctions. There have also been studies of volcanism, and some eruptions correspond to extinction, but many do not."
Arnold I. Miller, a paleobiologist and professor of geology at the University of Cincinnati, says the new study is striking because it establishes a clear relationship between the tempo of mass extinction events and changes in sea level and sediment: "Over the years, researchers have become fairly dismissive of the idea that marine mass extinctions like the great extinction of the Late Permian might be linked to sea-level declines, even though these declines are known to have occurred many times throughout the history of life. The clear relationship this study documents will motivate many to rethink their previous views."
Peters measured two principal types of marine shelf environments preserved in the rock record, one where sediments are derived from erosion of land and the other composed primarily of calcium carbonate, which is produced in-place by shelled organisms and by chemical processes. "The physical differences between these two types of marine environments have important biological consequences," Peters explains noting differences in sediment stability, temperature and the availability of nutrients and sunlight.
In the course of hundreds of millions of years the world's oceans have expanded and contracted in response to the shifting of the Earth's tectonic plates and to changes in climate. There were periods of the planet's history when vast areas of the continents were flooded by shallow seas such as the shark and mosasaur infested seaway that neatly split North America during the age of the dinosaurs.
As those epicontinental seas drained, animals like mosasaurs and giant sharks went extinct, and conditions on the marine shelves where life exhibited its greatest diversity in the form of things like clams and snails changed as well. The new Wisconsin study, Peters says, does not preclude other influences on extinction such as physical events like volcanic eruptions or killer asteroids, or biological influences such as disease and competition among species. But what it does do, he argues, is provide a common link to mass extinction events over a significant stretch of Earth history.
"The major mass extinctions tend to be treated in isolation by scientists," Peters says. "This work links them and smaller events in terms of a forcing mechanism, and it also tells us something about who survives and who doesn't across these boundaries. These results argue for a substantial fraction of change in extinction rates being controlled by just one environmental parameter."
The National Science Foundation (NSF)
Since the advent of life on Earth 3.5 billion years ago, scientists think there may have been as many as 23 mass extinction events, many involving simple forms of life such as single-celled microorganisms. Over the past 540 million years, there have been five well-documented mass extinctions, primarily of marine plants and animals, with as many as 75-95 percent of species lost. For the most part, scientists have been unable to pin down the causes of such dramatic events. In the case of the demise of the dinosaurs, scientists have a smoking gun, an impact crater that suggests dinosaurs were wiped out as the result of a large asteroid crashing into the planet. But the causes of other mass extinction events have been murky, at best.
"No matter what the ultimate driving extinction mechanisms might be at any one time, Professor Peters brings the repeated and resultant extinction on oceanic shelves front and forward where it belongs," says National Science Foundation (NSF) Program Manager Rich Lane. "This breakthrough speaks loudly to the future impending modern shelf extinction due to climate change on Earth."
Paleontologists have been chipping away at the causes of mass extinctions for almost 60 years, according to Peters, whose work was supported by NSF. "Impacts, for the most part, aren't associated with most extinctions. There have also been studies of volcanism, and some eruptions correspond to extinction, but many do not."
Arnold I. Miller, a paleobiologist and professor of geology at the University of Cincinnati, says the new study is striking because it establishes a clear relationship between the tempo of mass extinction events and changes in sea level and sediment: "Over the years, researchers have become fairly dismissive of the idea that marine mass extinctions like the great extinction of the Late Permian might be linked to sea-level declines, even though these declines are known to have occurred many times throughout the history of life. The clear relationship this study documents will motivate many to rethink their previous views."
Peters measured two principal types of marine shelf environments preserved in the rock record, one where sediments are derived from erosion of land and the other composed primarily of calcium carbonate, which is produced in-place by shelled organisms and by chemical processes. "The physical differences between these two types of marine environments have important biological consequences," Peters explains noting differences in sediment stability, temperature and the availability of nutrients and sunlight.
In the course of hundreds of millions of years the world's oceans have expanded and contracted in response to the shifting of the Earth's tectonic plates and to changes in climate. There were periods of the planet's history when vast areas of the continents were flooded by shallow seas such as the shark and mosasaur infested seaway that neatly split North America during the age of the dinosaurs.
As those epicontinental seas drained, animals like mosasaurs and giant sharks went extinct, and conditions on the marine shelves where life exhibited its greatest diversity in the form of things like clams and snails changed as well. The new Wisconsin study, Peters says, does not preclude other influences on extinction such as physical events like volcanic eruptions or killer asteroids, or biological influences such as disease and competition among species. But what it does do, he argues, is provide a common link to mass extinction events over a significant stretch of Earth history.
"The major mass extinctions tend to be treated in isolation by scientists," Peters says. "This work links them and smaller events in terms of a forcing mechanism, and it also tells us something about who survives and who doesn't across these boundaries. These results argue for a substantial fraction of change in extinction rates being controlled by just one environmental parameter."
The National Science Foundation (NSF)
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Mass Extinction Current Events and Mass Extinction News RSSAncient volcanic eruptions caused global mass extinction
A previously unknown giant volcanic eruption that led to global mass extinction 260million years ago has been uncovered by scientists at the University of Leeds.
Princeton geoscientist offers new evidence that meteorite did not wipe out dinosaurs
A Princeton University geoscientist who has stirred controversy with her studies challenging a popular theory that an asteroid wiped out the dinosaurs has compiled powerful new evidence asserting her position.
New blow for dinosaur-killing asteroid theory
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.
New theory on largest known mass extinction in the history of the earth
Did volatile halogenated gases from giant salt lakes at the end of the Permian Age lead to a mass extinction of species?
Study unravels why certain fishes went extinct 65 million years ago
Large size and a fast bite spelled doom for bony fishes during the last mass extinction 65 million years ago, according to a new study to be published March 31, 2009, in the Proceedings of the National Academy of Sciences.
No joy in discoveries of new mammal species -- only a warning for humanity, Paul Ehrlich says
In the era of global warming, when many scientists say we are experiencing a human-caused mass extinction to rival the one that killed off the dinosaurs, one might think that the discovery of a host of new species would be cause for joy.
New paper offers key insights into how new species emerge
This year marks both the bicentennial of Charles Darwin's birth and the 150th anniversary of the publication of his seminal work "On the Origin of Species."
Global warming link to amphibian declines in doubt
Evidence that global warming is causing the worldwide declines of amphibians may not be as conclusive as previously thought, according to biologists. The findings, which contradict two widely held views, could help reveal what is killing the frogs and toads and aid in their conservation.
Current mass extinction spurs major study of which plants to save
The Earth is in the midst of the sixth mass extinction of both plants and animals, with nearly 50 percent of all species disappearing, scientists say.
Extinction by asteroid a rarity
In geology as in cancer research, the silver bullet theory always gets the headlines and nearly always turns out to be wrong.
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THE GRAVITY THEORY OF MASS EXTINCTION: A New Unified Theory of Mass Extinction Explains The Rise and Fall of The Dinosaurs by John Stojanowski (Author) A new unified theory of mass extinction that identifies the primary cause for the 'Big Five' mass extinctions as a gravitational one. The theory proposed in this book posits a lowered surface gravity as a result of the coalescing of the continents that formed the supercontinent Pangea. The linkage of continental tectonic plate movement and the shifting of the Earth's inner iron core is described and is the underlying basis for changes in surface gravity. The gigantism of the sauropod dinosaurs and other Mesozoic life forms are attributed to reduced surface gravity as well as their gradual extinction as Pangea broke apart, resulting in increased gravitation. The rapid fall and rise of global sea levels during periods of mass extinction, unexplained by current mass extinction theories,... |
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Catastrophes and Lesser Calamities: The Causes of Mass Extinctions by Oxford University Press, USA In Catastrophes and Lesser Calamities, renowned geologist Tony Hallam takes us on a tour of the Earth's history, and of the cataclysmic events, as well as the more gradual extinctions, that have punctuated life on Earth throughout the past 500 million years. While comparable books in this field of study tend to promote only one likely cause of mass extinctions, such as extraterrestrial impact, volcanism, and or climatic cooling, Catastrophes and Lesser Calamities breaks new ground, as the first book to attempt an objective coverage of all likely causes, including sea-level and climatic changes, oxygen deficiency in the oceans, volcanic activity, and extraterrestrial impact. Hallam focuses on the so-called 'big five' mass extinctions, at the end of the Ordovician,... |
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Mass Extinctions and Their Aftermath by Oxford University Press, USA This is the first review of all the major mass extinctions in the history of life. It covers all groups of organisms - plant, animal, terrestrial, and marine - that have gone extinct alongside the geological and sedimentological evidence for environmental changes during the biotic crises. All proposed extinction mechanisms - climage change, meteorite impact, volcanisms - are critically assessed. The demise of the dinosaurs has been amply discussed, but this is the first time that this event has been put into the proper context of other extinction events. |
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Catastrophes and Lesser Calamities: The Causes of Mass Extinctions by Tony Hallam (Author) In Catastrophes and Lesser Calamities, renowned geologist Tony Hallam takes us on a tour of the Earth's history, and of the cataclysmic events, as well as the more gradual extinctions, that have punctuated life on Earth throughout the past 500 million years. While comparable books in this field of study tend to promote only one likely cause of mass extinctions, such as extraterrestrial impact, volcanism, and or climatic cooling, Catastrophes and Lesser Calamities breaks new ground, as the first book to attempt an objective coverage of all likely causes, including sea-level and climatic changes, oxygen deficiency in the oceans, volcanic activity, and extraterrestrial impact. Hallam focuses on the so-called 'big five' mass extinctions, at the end of the Ordovician,... |
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Mass Extinctions Starring: Mass Extinctions Evolution has been interrupted five times by major catastrophes, and 99.9 percent of all species of plants and animals that have ever lived on earth are now extinct. But large-scale destruction clears the way for new species to thrive--in fact, if the dinosaurs hadn't died out, humans may never have evolved. With such dramatic subject matter, you'd think it would be easy to produce a fascinating, thought-provoking documentary. Unfortunately, this is not the case with Mass Extinctions. Poor production quality consistently distracts from the program's attempted message. The sound is often not synchronized with the footage of scholars being interviewed. Although the program was filmed in 1993, the animation and graphics are on a par with high school filmstrips from the 1970s. To indicate the... |
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