Earth Science News  





. Stinking seas not to blame for 'mother of all mass extinctions'

This image shows annual mean surface temperatures in degrees Celsius at the time of the Permian extinction. It is based on a computer simulation generated by the Community Climate System Model at NCAR. Illustration Credit: Jeff Kiehl, NCARs
by Staff Writers
Paris (AFP) March 23, 2008
Scientists on Sunday said they had ruled out a key hypothesis to explain Earth's greatest extinction, when 95 percent of marine species and 70 percent of land species were wiped out.

Dubbed "the Great Dying" or "the mother of all mass extinctions," the catastrophe occurred around 250 million years ago at the end of the Permian era.

The event may have unfolded over millions of years, and an increasing number of clues testify to its severity, include the discovery worldwide of eerie, fossilised, mutant plant spores. What is unclear, though, is what caused it.

British researchers, reporting on Sunday in the journal Nature Geoscience, rule out a leading theory that the oceans became starved of oxygen and rich with sulphide, causing marine life to die out.

Clouds of hydrogen sulphide -- the same chemical that comes from rotting eggs -- rose from the seas and, abetted by methane released as a by-product of intense vulcanism, attacked the ozone layer, the stratospheric shield that filters ultraviolet-B light from the Sun.

On the ground, life was ravaged, goes this theory. Living things were poisoned by toxic levels of hydrogen sulphide and their DNA was shredded by solar radiation.

A team led by David Beerling of the University of Sheffield in northern England created a two-dimensional computer model of atmospheric chemistry to test this notion.

According to their calculations, the lower levels of the atmosphere in the tropics would have acted as an oxidising buffer, preventing the hydrogen sulphide from seriously damaging the ozone layer.

"These gases seem unlikely to be the cause of coincident terrestrial biotic extinctions," the paper says.

Other theories still in the arena include an impact, or series of impacts, by an asteroid, similar to the event believed to have wiped out the dinosaurs some 62 million years ago.

A "deep impact" of this kind would have generated a dust storm that smothered the planet, obscuring the Sun and shrivelling vegetation.

Another idea is that the planet was convulsed by a brief but fierce period of vulcanism which caused a lethal mixture of acid rain and global warming.

Community
Email This Article
Comment On This Article

Related Links
Darwin Today At TerraDaily.com




Tempur-Pedic Mattress Comparison

Newsletters :: SpaceDaily Express :: SpaceWar Express :: TerraDaily Express :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News
Study: Evolution creates complex animals
Bath, England (UPI) Mar 20, 2008
A British-led study of 550 million years of the fossil record has found evidence suggesting evolution drives animals to become increasingly more complex.

.
Get Our Free Newsletters Via Email
  



  • Louisiana System Built Homes Completes First Fortified For Safer Living Home
  • Mozambique tourist resort struggles to recover from cyclone
  • Mozambican government seeks urgent food aid after cyclone
  • Albania's blast toll mounts as rescuers look for victims

  • Curbing soot could blunt global warming: study
  • Envisat Makes First Ever Observation Of Regionally Elevated CO2 From Manmade Emissions
  • Indigenous people can offer climate change solutions: IUCN
  • Atlantic's Gulf Stream has huge influence on atmosphere

  • NASA Goddard Delivers Aquarius Radiometer To JPL
  • Brazil, Germany To Develop Night-Vision Radar Satellite
  • New Portrait Of Earth Shows Land Cover As Never Before
  • Great Splitting Icebergs

  • Analysis: Oil price-speculators link eyed
  • Outside View: Gazprom, Ukraine price rows
  • Analysis: Nigeria's labor woes
  • Analysis: Can biotechnology save ethanol?

  • Indonesia's bird flu situation 'grave'
  • Toll in Burkina meningitis epidemic exceeds 500
  • WHO warns more TB cases slipping through detection net
  • Bird flu outbreak in southern China: state media

  • Study: Evolution creates complex animals
  • Stinking seas not to blame for 'mother of all mass extinctions'
  • Nigeria is suspended from CITES wildlife trade pact
  • Rabbits To The Rescue Of The Reef

  • Eco-Friendly Pyrotechnics
  • NASA Satellite Measures Pollution From East Asia To North America
  • Bush administration tightens air pollution standards
  • Russia orders probe into Lake Baikal mill pollution

  • Clovis-Age Overkill Didn't Take Out California's Flightless Sea Duck
  • Analysis: Iraq progress missing women
  • Fossils of extinct human species found
  • China to stick with one-child policy

  • The content herein, unless otherwise known to be public domain, are Copyright 1995-2007 - SpaceDaily.AFP and UPI Wire Stories are copyright Agence France-Presse and United Press International. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by SpaceDaily on any Web page published or hosted by SpaceDaily. Privacy Statement