Navigation Links
The mystery of mass extinctions is no longer murky
Date:6/17/2008

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
dbanegas@nsf.gov
703-292-4489
National Science Foundation
Source:Eurekalert  

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:
*Name:
*Comment:
*Email:
Related Image:
The mystery of mass extinctions is no longer murky
(Date:4/11/2017)... -- NXT-ID, Inc. (NASDAQ:   NXTD ) ("NXT-ID" ... of independent Directors Mr. Robin D. Richards and ... furthering the company,s corporate governance and expertise. ... Gino Pereira , Chief Executive Officer ... guidance and benefiting from their considerable expertise as we move ...
(Date:4/5/2017)... April 4, 2017 KEY FINDINGS ... expand at a CAGR of 25.76% during the forecast ... the primary factor for the growth of the stem ... https://www.reportbuyer.com/product/4807905/ MARKET INSIGHTS The global stem cell ... application, and geography. The stem cell market of the ...
(Date:3/30/2017)... HONG KONG , March 30, 2017 ... developed a system for three-dimensional (3D) fingerprint identification by adopting ground ... technology into a new realm of speed and accuracy for use ... applications at an affordable cost. ... ...
Breaking Biology News(10 mins):
(Date:8/15/2017)... ... August 15, 2017 , ... Coffea arabica ... biotic and abiotic factors. During this educational webinar, participants will learn about the ... as gain a better understanding of how genomics is important for coffee breeding ...
(Date:8/11/2017)... 11, 2017  Market researcher Kalorama Information ... article regarding the telemedicine market.  The telemedicine ... Information.  The article, "Heart and Asthma ...  used information from Kalorama Information,s Remote Patient ... Market  (Sleep, Diabetes, Vital Signs /EKG ...
(Date:8/10/2017)... ... 09, 2017 , ... Teachers from three Philadelphia middle schools ... through the 16th, the University City Science Center will kick off the second ... Philadelphia-based middle school educators an opportunity for professional development related to STEM education. ...
(Date:8/10/2017)... (PRWEB) , ... August 10, 2017 , ... DrugDev ... new educational webinar to demonstrate how Good Clinical Practice (GCP) can be ... documents. In addition the webinar will discuss the importance of GCP compliance, how sites ...
Breaking Biology Technology: