No Safe Ground For Life To Stand On During Largest Mass Extinction
- No Safe Ground For Life To Stand On During Largest Mass Extinction
London, UK (SPX) Dec 01, 2005
The world's largest mass extinction was probably caused by poisonous
volcanic gas, according to research published today.
The research, published in the journal Geology, reveals vital clues
about the mass extinction at the end of the Permian period, 250
million years ago, when mammal-like reptiles known as synapsids
roamed the earth.
Many scientists had previously thought that an asteroid hitting the
earth or a deep-sea methane release had caused the extinction, which
obliterated more than two-thirds of reptile and amphibian families.
However, analysis of a unique set of molecules found in rocks taken
from the Dolomites in Italy has enabled scientists to build up a
picture of what actually happened. The molecules are the remains of
polysaccharides, large sugar-based structures common in plants and
soil, and they tell the story of the extinction.
The molecules date from the same time as a major volcanic eruption
that caused the greatest ever outpouring of basalt lava over vast
swathes of land in present day Siberia.
The researchers believe that the volcanic gases from the eruption,
which would have depleted earth's protective ozone layer and
acidified the land and sea, killed rooted vegetation. This meant
that soil was no longer retained and it washed into the surrounding
The chemistry of the rocks reveals that although the sugar molecules
were found in marine sediments, they derived from land, supporting
the theory that massive soil erosion caused them to end up in the
Soil materials in the oceans would have blocked out light and soaked
up oxygen. Analysis of rock chemistry suggests that after the soil
crisis on land, the marine ecosystem succumbed to the stresses of
environmental change and oceanic life faltered, completing a global
Dr Mark Sephton, from Imperial College London's Department of Earth
Sciences and Engineering and lead author of the research, said: "The
cause of the end Permian extinction has been highly controversial.
We show that the terrestrial ecosystem was the first to suffer. The
continent-wide nature of the event implies that it was caused by
something in the atmosphere. The unique chemical data indicates that
something fast and catastrophic happened on land."
Prof Henk Visscher of Utrecht University, also part of the research
team, commented: "Similar to the 'Dead Zone' nowadays spreading in
the Gulf of Mexico, the soil crisis could have caused a worldwide
expanse of uninhabitable low-oxygen conditions in shallow marine
waters. So what began on land ended in the sea. It seems there was
no place to hide at this time of great dying."
Dr Sephton believes that lessons can be learned in the present day
from the damage caused by the end Permian extinction: "Land
degradation is a worsening global problem thanks to human activity
and soil erosion has caused the loss of a third of arable land over
the last forty years. 35% of the Earth's land is now soil-free.
Identifying the nature of the end Permian soil crisis may help us
understand what is in store for us in the years ahead," he said.
The research was carried out by an international team of scientists
from the United Kingdom, the Netherlands and the United States.