Did a collision with a giant asteroid or comet change the shape of life on Earth forever?
It is widely agreed that such an object, 10 kilometers across, struck just off the coast of the Yucatan peninsula more than sixty million years ago. According to scientists who maintain that dinosaur extinction came quickly, the impact must have spelled the cataclysmic end. For many months, scientists conclude that dense clouds of dust blocked the sun’s rays, darkening and chilling Earth to deadly levels for most plants and, in turn, many animals. Then, when the dust finally settled, greenhouse gases created by the impact caused temperatures to skyrocket above pre-impact levels.In just a few years, according to this hypothesis, these frigid and sweltering climatic extremes caused the extinction of not just the dinosaurs, but of up to 70 percent of all plants and animals living at the time.
Thursday, February 7, 2013, this popular hypothesis has been smashed with a current study by Paul Renne, a geologist from the University Of California Berkeley, whose studies ties with mass extinction and volcanism. Contrary to popular belief, Dinosaurs may have not died from asteroids that have hit the earth.
Now what exactly might have caused to the distinction of these giants? Renne, for one, does not believe the asteroid impact was the sole reason for the dinosaurs’ demise. He says ecosystems already were in a state of deterioration due to a major volcanic eruption in India when the asteroid struck. “The asteroid strike provided the coup-de-grace for the final extinctions,” Renne said, adding that the theory was speculative, but backed by previous ties between mass extinction events and volcanic eruptions. Researchers said that the Earth’s climate may have been at a tipping point when a massive asteroid impacted into what is now known as Mexico’s Yucatan Peninsula which then triggered cooling temperature that wiped out the dinosaurs. The time between the asteroid’s arrival, marked by a 110 mile (80 kilometers) wide crater near Chicxulub (pronounced as “cheek-she-loob), Mexico, and the dinosaurs’ wipe out was said and believed to be as long as 300,000 years.
The theory that the dinosaurs’ extinction about 66 million years ago was linked to an asteroid impact was first proposed in 1980. The study said the events occurred within 33,000 years of each other. The study was based on high-precision radiometric dating techniques. The biggest piece of evidence was the Chicxulub crater off the Yucatan coast in Mexico. It is believed to have been formed by a nine kilometer wide object that melted rocks as it smashed into the surface of the earth, covering the atmosphere with debris that eventually rained down on Earth. Tektites, which are glassy spheres, shocked quartz and a layer of iridium-rich dust are still found around earth today. Renne and his colleagues re-analyzed both the dinosaur extinction date and the crater formation event and found they occurred within a much tighter window in time than previously known. The study looked at tektites from Haiti, tied to the asteroid impact site, and volcanic ash from the Hell Creek Formation in Montana, a source of many dinosaur fossils.
About 1 million years before the impact, Earth experienced six abrupt shifts in temperature of more than 2 degrees in continental mean annual temperatures, according to research cited by Renne and his co-authors. The swings of temperature include one shift of 6 to 8 degrees that happened about 100,000 years before the extinction of dinosaurs. “The brief cold snaps in the latest Cretaceous, though not necessarily of extraordinary magnitude, were particularly stressful to a global ecosystem that was well adapted to the long-lived preceding Cretaceous hothouse climate. The Chicxulub impact then provided a decisive blow to ecosystems,” Renne and his co-authors wrote in the book “Science.”