Featured Research

from universities, journals, and other organizations

Geological 'pulse' causes cycle of extinctions every 60 million years, scientists report

Date:
February 22, 2012
Source:
University of Chicago Press Journals
Summary:
A mysterious cycle of booms and busts in marine biodiversity over the past 500 million years could be tied to a periodic uplifting of the world's continents, scientists report.

A mysterious cycle of booms and busts in marine biodiversity over the past 500 million years could be tied to a periodic uplifting of the world's continents, scientists report in the March issue of The Journal of Geology.

The researchers discovered periodic increases in the amount of the isotope strontium-87 found in marine fossils. The timing of these increases corresponds to previously discovered low points in marine biodiversity that occur in the fossil record roughly every 60 million years. Adrian Melott, a Professor of Physics and Astronomy at the University of Kansas and the study's lead author, thinks these periodic extinctions and the increased amounts Sr-87 are linked.

"Strontium-87 is produced by radioactive decay of another element, rubidium, which is common in igneous rocks in continental crust," Melott said. "So, when a lot of this type of rock erodes, a lot more Sr-87 is dumped into the ocean, and its fraction rises compared with another strontium isotope, Sr-86."

An uplifting of the continents, Melott explains, is the most likely explanation for this type of massive erosion event.

"Continental uplift increases erosion in several ways," he said. "First, it pushes the continental basement rocks containing rubidium up to where they are exposed to erosive forces. Uplift also creates highlands and mountains where glaciers and freeze-thaw cycles erode rock. The steep slopes cause faster water flow in streams and sheet-wash from rains, which strips off the soil and exposes bedrock. Uplift also elevates the deeper-seated igneous rocks where the Sr-87 is sequestered, permitting it to be exposed, eroded, and put into the ocean."

The massive continental uplift suggested by the strontium data would also reduce sea depth along the continental shelf where most sea animals live. That loss of habitat due to shallow water, Melott and collaborators say, could be the reason for the periodic mass extinctions and periodic decline in diversity found in the marine fossil record.

"What we're seeing could be evidence of a 'pulse of the earth' phenomenon," Melott said. "There are some theoretical works which suggest that convection of mantle plumes, rather like a lava lamp, should be coordinated in periodic waves." The result of this convection deep inside Earth could be a rhythmic throbbing -- almost like a cartoon thumb smacked with a hammer -- that pushes the continents up and down.

Melott's data suggest that such pulses likely affected the North American continent. The same phenomenon may have affected other continents as well, but more research would be needed to show that, he says.


Story Source:

The above story is based on materials provided by University of Chicago Press Journals. Note: Materials may be edited for content and length.


Journal Reference:

  1. Adrian L. Melott, Richard K. Bambach, Kenni D. Petersen, and John M. McArthur. A ~60 Myr periodicity is common to marine-87Sr/86Sr, fossil biodiversity, and large-scale sedimentation: what does the periodicity reflect? The Journal of Geology, March 2012

Cite This Page:

University of Chicago Press Journals. "Geological 'pulse' causes cycle of extinctions every 60 million years, scientists report." ScienceDaily. ScienceDaily, 22 February 2012. <www.sciencedaily.com/releases/2012/02/120222132932.htm>.
University of Chicago Press Journals. (2012, February 22). Geological 'pulse' causes cycle of extinctions every 60 million years, scientists report. ScienceDaily. Retrieved April 23, 2014 from www.sciencedaily.com/releases/2012/02/120222132932.htm
University of Chicago Press Journals. "Geological 'pulse' causes cycle of extinctions every 60 million years, scientists report." ScienceDaily. www.sciencedaily.com/releases/2012/02/120222132932.htm (accessed April 23, 2014).

Share This



More Plants & Animals News

Wednesday, April 23, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Monkeys Are Better At Math Than We Thought, Study Shows

Monkeys Are Better At Math Than We Thought, Study Shows

Newsy (Apr. 23, 2014) A Harvard University study suggests monkeys can use symbols to perform basic math calculations. Video provided by Newsy
Powered by NewsLook.com
Raw: Leopard Bites Man in India

Raw: Leopard Bites Man in India

AP (Apr. 22, 2014) A leopard caused panic in the city of Chandrapur on Monday when it sprung from the roof of a house and charged at rescue workers. (April 22) Video provided by AP
Powered by NewsLook.com
Iowa College Finds Beauty in Bulldogs

Iowa College Finds Beauty in Bulldogs

AP (Apr. 22, 2014) Drake University hosts 35th annual Beautiful Bulldog Contest. (April 21) Video provided by AP
Powered by NewsLook.com
805-Pound Shark Caught Off The Coast Of Florida

805-Pound Shark Caught Off The Coast Of Florida

Newsy (Apr. 22, 2014) One Florida fisherman caught a 805-pound shark off the coast of Florida earlier this month. Video provided by Newsy
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