Navigation Links
The mystery of mass extinctions is no longer murky

If 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."


Contact: Diane Banegas
National Science Foundation

Related biology news :

1. Scientists tackle mystery mountain illness
2. Folate mystery finally solved
3. Men shed light on the mystery of human longevity, study finds
4. Magnetic snakes control fluids, gravity-defying droplets, and solving a dragonfly mystery
5. Cassini on the trail of a runaway mystery
6. Time-sharing tropical birds key to evolutionary mystery
7. 480-million-year-old fossil sheds light on 150-year-old paleontological mystery
8. ASU professor helps solve mystery of glassy water
9. Ancient mystery solved
10. UCLA researchers solve decade-old mystery
11. Has the mystery of the Antarctic ice sheet been solved?
Post Your Comments:
Related Image:
The mystery of mass extinctions is no longer murky
(Date:11/12/2015)...   Growing need for low-cost, easy to ... paving the way for use of biochemical sensors ... in clinical, agricultural, environmental, food and defense applications. ... medical applications, however, their adoption is increasing in ... emphasis on improving product quality and growing need ...
(Date:11/9/2015)... JOSE, Calif. , Nov. 9, 2015  Synaptics ... human interface solutions, today announced broader entry into the ... vehicle-specific solutions that match the pace of consumer electronics ... and biometric sensors are ideal for the automotive industry ... vehicle. Europe , ...
(Date:10/29/2015)... Daon, a global leader in mobile biometric ... new version of its IdentityX Platform , IdentityX ... have already installed IdentityX v4.0 and are ... FIDO UAF certified server component as an option ... features. These customers include some of the largest and ...
Breaking Biology News(10 mins):
(Date:11/30/2015)... Human Longevity, Inc. (HLI), the genomics-based, technology-driven ... Genomics, Inc., a leading genome informatics company offering highly ... The San Diego -based company has ... and Co-founder, Ashley Van Zeeland , Ph.D., who is ... of the deal were not disclosed. ...
(Date:11/30/2015)... DIEGO , Nov. 30, 2015  HUYA Bioscience ... China,s pharmaceutical innovations, today announced it ... Drug Development Fund (KDDF) to foster collaboration between KDDF ... development and commercialization of healthcare products for the global ... as an important source of new innovative preclinical and ...
(Date:11/30/2015)... , Nov. 30, 2015  AbbVie, is introducing ... focuses on a daily routine for managing the life-long ... medication can affect the way the body absorbs it ... their a daily routine are important. The goal of ... patients better manage their hypothyroidism by establishing a daily ...
(Date:11/30/2015)... Nov. 30, 2015  Northwest Biotherapeutics (NASDAQ: NWBO ... personalized immune therapies for solid tumor cancers, announced today ... independent director, and the Company welcomes Neil Woodford,s ... a recent anonymous internet report on NW Bio.  The ... Linda Powers stated, "We agree with Mr. ...
Breaking Biology Technology: