Featured Research

from universities, journals, and other organizations

New Evidence Indicates Huge Vegetation Loss Accompanied Mass Extinction

Date:
September 14, 2000
Source:
University Of Washington
Summary:
The greatest mass extinction in Earth history eliminated 85 percent to 90 percent of all marine and land vertebrate species 250 million years ago, at the end of the Permian Period and the beginning of the Triassic. New evidence from researchers at the University of Washington and the South African Museum shows the extinction was accompanied by a massive loss of vegetation, causing major changes in river systems.

The greatest mass extinction in Earth history eliminated 85 percent to 90 percent of all marine and land vertebrate species 250 million years ago, at the end of the Permian Period and the beginning of the Triassic. New evidence from researchers at the University of Washington and the South African Museum shows the extinction was accompanied by a massive loss of vegetation, causing major changes in river systems.

Probing sedimentary layers in the Karoo Basin of South Africa, the scientists found evidence that, with the loss of deep-rooting plants, meandering river systems changed rapidly to braided systems. Braided streams run much straighter and faster and branch out for short distances before merging back to the primary stream. They also cause much faster sediment buildup because vegetation is not holding streamside soil in place and it is easily swept away by the faster-moving water.

Using data from the Karoo and elsewhere, the scientists attribute the drastic change in river character to a catastrophic global die off of vegetation that likely resulted from the same cause as the mass extinction among marine and land animals.

Peter Ward, a UW geological sciences professor, along with David Montgomery, a UW associate geological sciences professor, and Roger Smith, the South African Museum's curator of geology, publish their findings in the Sept. 8 issue of the journal Science.

Sedimentary layers from the Permo-Triassic boundary were examined at seven different sites scattered across 250 miles of the Karoo Basin, and the researchers found striking similarities in the evidence for a rapid shift from meandering to braided streams.

Major tectonic activity could change streams from meandering to braided, Ward said. However, recent studies have shown there was no major tectonic activity at the time of the Permo-Triassic extinction, which occurred when the Earth's land was still locked in a supercontinent called Pangea.

Braided streams were common until the Silurian Period some 400 million years ago, but then gave way to meandering streams as plant life evolved. Today it is rare to see a braided stream unless it is in a place, like Mount St. Helens in Washington state, where the landscape has been denuded by a catastrophic event such as a volcanic eruption.

"The thing we take so for granted now - meandering rivers - is a very recent feature on Earth," Ward said. "This didn't appear until the Silurian, when land plants started to take over the Earth."

The sudden reappearance of braided streams, probably on a global scale, 250 million years ago is strong evidence of a major catastrophe that wiped out plant life as well as much of animal life, Ward said. He noted that plant life emerged again relatively quickly at the beginning of the Triassic Period.

A number of potential causes for the mass extinction have been postulated, including the impact of an asteroid or comet, environmental shifts, volcanism or the overturning of the oceans to release trapped gases into the atmosphere. In their research, paid for by a National Science Foundation grant, Ward, Montgomery and Smith do not speculate which, if any, of the theories is correct. But they say that the way plant life disappeared indicates events happened very quickly on a geological scale.

"Whenever you describe something as happening in thousands, rather than millions, of years, that's very fast geologically speaking," Ward said. "The new evidence helps us understand how rapid this was, because the transition from meandering to braided streams was quick. And I think the most important thing is that it tells us how catastrophic this was. It was the most catastrophic event in Earth history, or at least in the history of life."


Story Source:

The above story is based on materials provided by University Of Washington. Note: Materials may be edited for content and length.


Cite This Page:

University Of Washington. "New Evidence Indicates Huge Vegetation Loss Accompanied Mass Extinction." ScienceDaily. ScienceDaily, 14 September 2000. <www.sciencedaily.com/releases/2000/09/000913212211.htm>.
University Of Washington. (2000, September 14). New Evidence Indicates Huge Vegetation Loss Accompanied Mass Extinction. ScienceDaily. Retrieved July 30, 2014 from www.sciencedaily.com/releases/2000/09/000913212211.htm
University Of Washington. "New Evidence Indicates Huge Vegetation Loss Accompanied Mass Extinction." ScienceDaily. www.sciencedaily.com/releases/2000/09/000913212211.htm (accessed July 30, 2014).

Share This




More Plants & Animals News

Wednesday, July 30, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: Thousands Flocking to German Crop Circle

Raw: Thousands Flocking to German Crop Circle

AP (July 30, 2014) Thousands of people are trekking to a Bavarian farmer's field to check out a mysterious set of crop circles. (July 30) Video provided by AP
Powered by NewsLook.com
Concern Grows Over Worsening Ebola Crisis

Concern Grows Over Worsening Ebola Crisis

AFP (July 30, 2014) Pan-African airline ASKY has suspended all flights to and from the capitals of Liberia and Sierra Leone amid the worsening Ebola health crisis, which has so far caused 672 deaths in Guinea, Liberia and Sierra Leone. Duration: 00:43 Video provided by AFP
Powered by NewsLook.com
At Least 20 Chikungunya Cases in New Jersey

At Least 20 Chikungunya Cases in New Jersey

AP (July 30, 2014) At least 20 New Jersey residents have tested positive for chikungunya, a mosquito-borne virus that has spread through the Caribbean. (July 30) Video provided by AP
Powered by NewsLook.com
Raw: Otters Enjoy Water Slides at Japan Zoo

Raw: Otters Enjoy Water Slides at Japan Zoo

AP (July 30, 2014) River otters were hitting the water slides to beat the summer heatwave on Wednesday at Ichikawa City's Zoological and Botanical Garden. (July 30) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins