Volcano eruptions triggered mass extinction before the age of dinosaurs 200 million years ago

via Tallbloke’s Talkshop
http://ift.tt/1WIzElD

Is there a contradiction in this IB Times report? First it says volcanism causes cooling, then we’re told the resulting volcanic CO2 could have caused warming.

High concentration of mercury identified in ancient sediments suggest that large-scale episodes of volcanism coincided with the end-Triassic mass extinction around 201 million years ago.

It is likely that these huge pulses of volcanic activity led to great environmental perturbations, leading to the extinction of many species living on Earth at the time and setting the scene for the dawn of the dinosaurs.

Previous studies had already shown that volcanic activity was happening around the time of the extinction and there was some evidence for an increase in the concentration of carbon dioxide (CO2) in the atmosphere.

Scientists thought that volcanic gases such as CO2 might have been an important contributor to the extinction event.

However, the global extent of the volcanic fluctuations at the end of the Triassic remained unknown and more research was needed to confirm the role of volcanic CO2.

Mercury levels

In a study now published in the journal PNAS, scientists have examined sediments and volcanic rocks which had formed around the end of the Triassic, looking for fluctuations in mercury – an important element released in volcanic gas.

“You want to look for something like mercury that is not too abundant in the earth’s surface reservoirs and that comes out of volcanoes in significant quantities. That way the signals from volcanism are easier to spot. Mercury also has a sufficiently long atmospheric lifetime that it stays in the atmosphere long enough to get far enough away from the volcano itself, to actually be seen in sediments around the world,” study author Tamsin Mather of Oxford University, told IBTimes UK.

At five of the six locations studied, the researchers identified pulses of elevated mercury in the sediment layers, in strata formed at the end-Triassic extinction and between it and the Triassic–Jurassic boundary, separated by approximately 200,000 years. These elevated mercury concentrations imply repeated episodes of large-scale volcanism over that time.

Continued here.

Talkshop note – the closing paragraph starts:
“Warming and cooling due to volcanic activity can have a range of potential knock-on effects on Earth.”