The cold exterminated all of them
Through age determinations that are using the radioactive decay of uranium, scientists have discovered that one of the greatest mass extinctions was due to an ice age and not to a warming of Earth temperature
Through age determinations that are using the radioactive decay of uranium, scientists have discovered that one of the greatest mass extinctions was due to an ice age and not to a warming of Earth temperature
The Earth has known several mass extinctions over the course of
its history. One of the most important happened at the Permian-Triassic
boundary 250 million years ago. Over 95% of marine species disappeared and, up
until now, scientists have linked this extinction to a significant rise in
Earth temperatures. But researchers from the University of Geneva (UNIGE),
Switzerland, working alongside the University of Zurich, discovered that this
extinction took place during a short ice age which preceded the global climate
warming. It’s the first time that the various stages of a mass extinction have
been accurately understood and that scientists have been able to assess the
major role played by volcanic explosions in these climate processes. This
research, which can be read in Scientific Reports, completely calls
into question the scientific theories regarding these phenomena, founded on the
increase of CO2 in the atmosphere, and paves the way for a new vision of the
Earth’s climate history.
Teams of researchers led by Professor Urs Schaltegger from the
Department of Earth and Environmental Sciences at the Faculty of Science of the
UNIGE and by Hugo Bucher, from the University of Zürich, have been working on
absolute dating for many years. They work on determining the age of minerals in
volcanic ash, which establishes a precise and detailed chronology of the
earth’s climate evolution. They became interested in the Permian-Triassic
boundary, 250 million years ago, during which one of the greatest mass
extinctions ever took place, responsible for the loss of 95% of marine species.
How did this happen? for how long marine biodiversity stayed at very low levels
?
A technique founded on the radioactive decay of uranium
Researchers worked on sediment layers in the Nanpanjiang basin
in southern China. They have the particularity of being extremely well
preserved, which allowed for an accurate study of the biodiversity and the
climate history of the Permian and the Triassic. “We made several cross-sections
of hundreds of metres of basin sediments and we determined the exact positions
of ash beds contained in these marine sediments,” explained Björn Baresel,
first author of the study. They then applied a precise dating technique based
on natural radioactive decay of uranium, as Urs Schaltegger added: “In the
sedimentary cross-sections, we found layers of volcanic ash containing the
mineral zircon which incorporates uranium. It has the specificity of decaying
into lead over time at a well-known speed. This is why, by measuring the
concentrations of uranium and lead, it was possible for us to date a sediment
layer to an accuracy of 35,000 years, which is already fairly precise for
periods over 250 million years.”
Ice is responsible for mass extinction
By dating the various sediment layers, researchers realised that
the mass extinction of the Permian-Triassic boundary is represented by a gap in
sedimentation, which corresponds to a period when the sea-water level
decreased. The only explanation to this phenomenon is that there was ice, which
stored water, and that this ice age which lasted 80,000 years was sufficient to
eliminate much of marine life. Scientists from the UNIGE explain the global
temperature drop by a stratospheric injection of large amounts of sulphur
dioxide reducing the intensity of solar radiation reaching the surface of the
earth. “We therefore have proof that the species disappeared during an ice age
caused by the activity of the first volcanism in the Siberian Traps,” added Urs
Schaltegger. This ice age was followed by the formation of limestone deposits
through bacteria, marking the return of life on Earth at more moderate
temperatures. The period of intense climate warming, related to the emplacement
of large amounts of basalt of the Siberian Traps and which we previously
thought was responsible for the extinction of marine species, in fact happened
500,000 years after the Permian-Triassic boundary.
This study therefore shows that climate warming is not the only
explanation of global ecological disasters in the past on Earth: it is
important to continue analysing ancient marine sediments to gain a deeper
understanding of the earth’s climate system.
https://wattsupwiththat.com/2017/03/06/shock-finding-p-t-mass-extinction-was-due-to-an-ice-age-and-not-to-warming/
