International Team of Scientists Consider a Variety of Factors in Demise of the Dinosauria
It was American father and son, Luis and Walter Alvarez who publicised the discovery of a world-wide layer of clay rich in the rare Earth element iridium in rocks known as the K-T boundary. The K-T boundary marks the border between the Cretaceous and the Tertiary. These American scientists argued that the iridium was deposited after an impact event, a collision between our planet and an exterrestrial object such as a meteorite or asteroid. This global catastrophe has been proposed as one of the main causes of the mass extinction event that marked the end of the Mesozoic and saw something like seventy percent of all life on land wiped out – including the Dinosauria. Time to reconsider the question: what caused the extinction of the dinosaurs?
Cretaceous Mass Extinction
However, other factors may have played a significant role in the demise of the dinosaurs and a team of international researchers have published papers detailing a ten year study into the strata and fossil record of northeastern Asia. They conclude that rising sea levels, volcanism and climate change were also very significant in the extinction of the mega fauna in this particular part of the world.
These new findings suggest that a prehistoric exterrestrial impact is not solely responsible for wiping out the dinosaur population in northeast Asia sixty-six million years ago. Chinese media is reporting that the scientists claim that the end of the dinosaur’s reign in some regions of northeast Asia can be linked to several other factors, including volcanic eruption, climate change and dramatic drops in sea level. The Chinese led study, involving thirty scientists from eight different countries has yielded powerful evidence challenging the dominant, impact theory, although scientists remain fairly confident that the Chicxulub crater in the Yucatan peninsula is evidence of a large impact event approximately sixty-six million years ago.
The study was made public during an ongoing seminar of geology and palaeontology in Jiayin, a county in northeastern Heilongjiang Province, where scientists have found fossils of dinosaurs living just before this group of reptiles extinction.
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The scientists, including experts from Russia, the U.S., Germany, Belgium, Britain, Japan and the Republic of Korea, were led by Sun Ge of Jilin University in northeast China. Together, they have spent the past ten years studying the extinction of dinosaurs.
The study showed that in Jiayin the K-T boundary, the geologic boundary between the rocks of the Cretaceous and Tertiary periods, does not contain high-levels of iridium, a radioactive element that linked an asteroid strike to the extinction of dinosaurs. This may be the case as although, the Chicxulub crater indicates a collision with an object at least ten kilometres in length, the fall out from the resulting explosion may not have reached northeastern Asia, leaving no tell-tale traces of iridium.
Among conflicting and controversial hypotheses explaining dinosaur extinction, the asteroid theory is the only one that has been proven by scientific evidence and is universally recognised by scientists, Sun commented.
Scientists believe a giant asteroid/meteorite that hit the earth about sixty-six million years ago sealed the fate of dinosaurs forever with huge pyroclastic clouds, shock-waves, earthquakes and tidal waves as well as extensive fires. Many palaeontologists believe that as dust and smoke filled the atmosphere, the sun was obscured and the planet was plunged into a “nuclear winter”. Most large land animals and many forms of marine life such as the mosasaurs, ammonites and belemnites became extinct. However, this new study suggests that volcanic activities around that time greatly impacted the environment of the Jiayin area and could be to blame for the mass extinction. Certainly, these dramatic changes in the climate and atmosphere may well have contributed to environmental stress.
Geologic features of and around the K-T boundary in Jiayin are identical to those of and around the same layer in Russian regions of Siberia and the Far East, said Sun Ge.
This is not the first time (or do we at Everything Dinosaur suspect the last time), the asteroid extinction theory has been challenged. To read a recent article on this debate: Impact Extinction Theory Challenged – Was it Global Cooling?
Regions in northeast Asia had similar geographic environments sixty-five million years ago, where volcanic eruption, climate cooling and up to 100-metre drops in sea-level might have been the major factors that wiped out the dinosaurs, said Akhmetiev M, a Russian geologist who participated in the program.
According to Sun, the world’s 105 sections of K-T boundary suggest a mega-wipeout sixty-six million years ago that destroyed over seventy percent of all the Earth’s species, including the dinosaurs.
However in conclusion the scientists state that the extinction of dinosaurs was probably caused by different factors in different regions, and an extraterrestrial impact was probably not the single cause of the Dinosauria extinction.
To read another article on the effect of volcanism on the extinction of the dinosaurs: Blame the Deccan Traps.