Carbon dioxide, the killer gas in today's world seems to have been the culprit aeons ago too. It has been identified as the gas which possibly led to mass extinctions some 250 million years ago
IT WAS 250 million years ago that life
took its first beating - the worst ever -
when mass extinctions marked the end
of the Permian period. A group of
American palaeontologists say that they
have evidence to prove that the extinctions in the Permian period, which
devoured 90 per cent of all genera in the
oceans, may have been triggered by a
belch of deep sea carbon dioxide
(Science, Vol 270, No 5241).
Researchers Andrew Knoll of the
Harvard University, Richard Bambach
of Virginia Polytechnic Institute and
State University and sedimentologist
John Grotzinger of the Massachusetts
Institute of Technology in the US, recognised a slide of a layered rock shown to
them by a colleague, to be an inorganic
carbon precipitate - carbonate - from
the late Permian period.
Carbonates are usually produced
from the remains of once living animals.
During the five cycles of glaciation in
the late Precambrian period between
600 million and 800 million years ago,
however, carbonates precipitated
directly from the seawater, without the
help of living beings. This could have
occurred when the concentration of dissolved carbon dioxide became very
high.
The palaeontologists propose that
the period witnessed a shutdown in the
circulation of the deep oceans. Continents then came to be huddled in a
supercontinent, Pangaea. With no continental ice sheets to chill surface waters,
the deep waters became stagnant. As
phytoplanktons on the surface waters
continued extracting carbon dioxide
from the atmosphere, converting it into
organic matter that sank and oxidised to
carbon dioxide, the result was a hike in
the deep sea carbon dioxide content.
We are a voice to you; you have been a support to us. Together we build journalism that is independent, credible and fearless. You can further help us by making a donation. This will mean a lot for our ability to bring you news, perspectives and analysis from the ground so that we can make change together.
Comments are moderated and will be published only after the site moderator’s approval. Please use a genuine email ID and provide your name. Selected comments may also be used in the ‘Letters’ section of the Down To Earth print edition.