Navigation Links
Meteor no longer prime suspect in great extinction
Date:10/25/2007

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 fueled by volcanic eruptions and global warming was the likely cause of the Great Dying 250 million years ago, said USC doctoral student Catherine Powers.

Writing in the November issue of the journal Geology, Powers and her adviser David Bottjer, professor of earth sciences at USC, describe a slow decline in the diversity of some common marine organisms.

The decline began millions of years before the disappearance of 90 percent of Earths species at the end of the Permian era, Powers shows in her study.

More damaging to the meteor theory, the study finds that organisms in the deep ocean started dying first, followed by those on ocean shelves and reefs, and finally those living near shore.

Something has to be coming from the deep ocean, Powers said. Something has to be coming up the water column and killing these organisms.

That something probably was hydrogen sulfide, according to Powers, who cited studies from the University of Washington, Pennsylvania State University, the University of Arizona and the Bottjer laboratory at USC.

Those studies, combined with the new data from Powers and Bottjer, support a model that attributes the extinction to enormous volcanic eruptions that released carbon dioxide and methane, triggering rapid global warming.

The warmer ocean water would have lost some of its ability to retain oxygen, allowing water rich in hydrogen sulfide to well up from the deep (the gas comes from anaerobic bacteria at the bottom of the ocean).

If large amounts of hydrogen sulfide escaped into the atmosphere, the gas would have killed most forms of life and also damaged the ozone shield, increasing the level of harmful ultraviolet radiation reaching the planets surface.

Powers and others believe that the same deadly sequence repeated itself for another major extinction 200 million years ago, at the end of the Triassic era.

There are very few people that hang on to the idea that it was a meteorite impact, she said. Even if an impact did occur, she added, it could not have been the primary cause of an extinction already in progress.

In her study, Powers analyzed the distribution and diversity of bryozoans, a family of marine invertebrates.

Based on the types of rocks in which the fossils were found, Powers was able to classify the organisms according to age and approximate depth of their habitat.

She found that bryozoan diversity in the deep ocean started to decrease about 270 million years ago and fell sharply in the 10 million years before the mass extinction that marked the end of the Permian era.

But diversity at middle depths and near shore fell off later and gradually, with shoreline bryozoans being affected last, Powers said.

She observed the same pattern before the end-Triassic extinction, 50 million years after the end-Permian.


'/>"/>

Contact: Carl Marziali
marziali@usc.edu
213-740-4751
University of Southern California
Source:Eurekalert

Related biology news :

1. Relic of life in that Martian meteorite? A fresh look
2. Far more than a meteor killed dinos
3. Innovative coating could give medical implants a longer life
4. Fluorescing lab worms signal longer life spans
5. Discoveries by UAB and Florida scientists may help transplanted organs survive longer
6. Lands surface change on Alaska tundra creating longer, warmer summers in Arctic
7. New antifreeze protein found in fleas may allow longer storage of transplant organs
8. Fish evolve a longer lifespan by evolving a longer reproductive period, researchers find
9. Chocolate milk could be key to longer, healthier life
10. Genetically altered mice no longer like cocaine
11. Evolutionary forces explain why women live longer than men
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:4/11/2017)... , Apr. 11, 2017 Research and ... Market 2017-2021" report to their offering. ... The global eye tracking market to grow at a ... report, Global Eye Tracking Market 2017-2021, has been prepared based on ... covers the market landscape and its growth prospects over the coming ...
(Date:4/11/2017)... , April 11, 2017 NXT-ID, ... security technology company, announces the appointment of independent Directors Mr. ... to its Board of Directors, furthering the company,s corporate ... ... NXT-ID, we look forward to their guidance and benefiting from ...
(Date:4/5/2017)... April 5, 2017  The Allen Institute for Cell ... Explorer: a one-of-a-kind portal and dynamic digital window into ... data, the first application of deep learning to create ... cell lines and a growing suite of powerful tools. ... these and future publicly available resources created and shared ...
Breaking Biology News(10 mins):
(Date:10/12/2017)... ... October 12, 2017 , ... ... announced today that they have entered into a multiyear collaboration to identify and ... researchers with additional tools for gene editing across all applications. , Under the ...
(Date:10/12/2017)... ... October 12, 2017 , ... ... analysis platform specifically designed for life science researchers to analyze and interpret ... Rosalind Franklin, who made a major contribution to the discovery of the ...
(Date:10/11/2017)... ... 11, 2017 , ... ComplianceOnline’s Medical Device Summit is back for its 4th ... in San Francisco, CA. The Summit brings together current and former FDA office bearers, ... and government officials from around the world to address key issues in device compliance, ...
(Date:10/11/2017)... Tbilisi, Georgia (PRWEB) , ... October 11, 2017 , ... ... disaster, taking the lives of over 5.5 million people each year. Especially those living ... the greenovative startup Treepex - based in one of the most pollution-affected countries globally ...
Breaking Biology Technology: