Home Evolution asteroid-volcano combo took out dinosaurs

asteroid-volcano combo took out dinosaurs

A team at Berkeley is arguing that both an asteroid and volcanic activity were responsible for the KT extinction event. Massive changes to the climate and other factors then likely wiped out the long dominant dinosaurs.

Ever since humanity discovered fossilized dinosaur bones, we’ve wondered what happened to the giant beasts. Over the years tons of theories have been proposed, and over the last few decades two have emerged as the most favored and likely causes. Lately, many researchers and laymen have leaned towards the idea that a giant asteroid collision with the Earth ultimately brought the dinosaurs down. Despite the popularity of this theory, some have continued to advocate that volcanic explosions, which also occurred during the KT extinction event, were what finally brought the dinos down.

Now, a team of Berkeley-based scientists are suggesting a sort of compromise. This compromise isn’t being made for the sake of civility, however, but is instead based on cold, hard science. According to a recent study that will soon be published in Science, researchers argue that the asteroid impact may have accelerated the volcano explosions, and the combined fallout from both catastrophes may have been what ultimately drove the dinosaurs extinct. It’s even possible that the asteroid impact on its own would not have been powerful enough to wipe out the dinosaurs.

The researchers from Berkeley echo earlier statements from reports made at Princeton University. Only this time around, the scientists had more data to back their theories up.

The researchers came to the double-whammy conclusion after collecting some 700 rock samples from India. The rocks were taken from the “Deccan Traps,” a 200,000 square kilometer basalt formation that can be as deep as a mile thick. The formation was created by a massive flow of lava and is one of the largest volcanic formations on earth. They can be found in West-central India.

Researchers found that massive amounts of lava were flowing before the asteroid hit, but the flow was beginning to slowly taper off. Once the asteroid struck, however, more lava began to flow, doubling in output within 50,000 years after the impact. This suggests that the asteroid may have reignited the massive flow of lava that roughly correspond with the KT extinction period.

Between the asteroid and the lava, huge amounts of ash and other contaminants were injected into the atmosphere. These pollutants blocked out the sun, depriving many plants of the light needed to grow, and caused massive changes in the climate, among other things.  Huge numbers of species died out in the ensuing chaos, with an estimated 75 percent of all animal species believed to have gone extinct.

Importantly, the period of heightened volcanic activity lasted for about 500,000 years. It was only after the volcanoes began to die down that species diversity began to expand. By the time life began to fully repopulate the Earth, however, all of the dinosaurs had died out.

The two-punch theory was developed and is now being pushed by geologists and other researchers at the University of California, Berkeley. Given that both the asteroid impact and a rapid increase in volcanic activity occurred during the same rough time period, the hypothesis that both contributed to the dinosaur extinction makes sense.

A look at the two-punch theory

The asteroid theory has emerged as the most popular theory for killing off the dinosaurs. In 1991 scientists found a massive 110 mile wide crater off the coast of the Yucatan in Mexico. The now-named Chicxulub crater was created by an asteroid that scientists believe measured about 6 miles wide. When the asteroid collided with the Earth it would have unleashed a force roughly equivalent to 1 billion times the amount of energy released by the bombs that destroyed Hiroshima and Nagasaki.

This massive explosion would have ejected huge amounts of dust into the atmosphere. While millions, if not billions of dinosaurs probably perished due to the direct impact of the meteor, it was most likely the dust that had the biggest impact. Once dust was ejected into the air, it would have dramatic impacts on the climate, and also would have deprived plants of the light needed to power photosynthesis.

Still, while the asteroid theory has emerged as the most popular explanation, scientists have also found evidence that the Earth was experiencing massive amounts of volcanic activity during the same time frame as the KT extinction event. Up until now, the two theories had been competing with one another.

Proponents of the volcanic theory have pointed out that massive amounts of lava was flowing for tens of thousands of years in present day India. The huge flow of lava would have been pretty much unprecedented, and would have released massive amounts of noxious gases, such as sulfur and carbon dioxide, into the atmosphere.

It’s important to remember that dinosaurs lived in a relatively warm, wet, and stable climate. They had spent millions upon millions of years evolving within this climate. The dramatic weather changes that would have been created by both the volcanoes and the asteroid impact would have put dinosaurs in the worst possible position for survival. Their millions of years of adaption to that warm, stable climate, and their sometimes massive size (which would require huge amounts of food) that allowed them to rule the earth was suddenly a detriment.

KT among most extensive extinctions ever

The Cretaceous–Tertiary extinction event, aka KT, occurred roughly 66 million years ago, wiping out most species of dinosaurs once and for all. Dinosaurs had survived previous extinction level events, even though many species died off. The only dinosaurs species that is believed to have survived KT was a small number of archosaurs that gave rise to birds and crocodiles.

The KT extinction event was essential for clearing the Earth of large species, and giving mammals a chance to thrive. While dinosaurs had dominated previous eras, after KT the “meek” really did inherit the earth. Small, rodent sized mammals would eventually evolve into primates, elephants, whales, and everything other type of mammal.

Interestingly, while mammals couldn’t compete with dinosaurs, it turns out that they were perfect for surviving the KT event. All major mammalian species of the time are believed to have survived the event. These small, hardy mammals that for so long walked in the shadows of the dinosaurs would have been in a much better position to survive the dramatic changes in the global environment following the dramatic two-punch apocalypse.

The importance of the KT extinction event that wiped out the dinosaurs cannot be underestimated. The event was one of the most extensive extinction events in the Earth’s history. Most importantly, it gave mammals a chance to emerge. While the exact causes of the KT event remain debated, the rapid rate at which dinosaur and other species died off suggests that it must have been a catastrophic incident.

Other theories on dino extinction

Besides volcanic activity and asteroids, various other theories have been put forward over the years. One theory is that small mammals evolved to eat eggs, and ultimately pushed dinos into extinction by limiting their ability to reproduce. Another theory is that shifts in the tectonic plates caused changes in the atmosphere (primarily cooling), and the dinosaurs were unable to adapt.

Both volcanic activity and an asteroid (or comet) impact have emerged as the most popular theories. They are the most probable, at least based on what we know from the fossil record.

It is also believed that meteor impacts could potentially cause seismic and volcanic activities.

KT not the only extinction event

The KT extinction event wasn’t the first or only extinction level event observed on planet earth. An extinction level event refers to a massive drop off in both the amount and diversity of life found on the Earth.

The cause of the world’s first extinction level event (as far as we know) might surprise you. The Great Oxygenation Event was apocalyptic in proportions and occurred roughly 2.3 billion years ago. While oxygen is now necessary for most life to exist on earth, a wide variety of simple anaerobic lifeforms existed on the planet billions of years ago.

Huge amounts of simple bacterias thrived in the Earth’s early oceans. These simple bacterias did not need oxygen to survive, and in fact oxygen was poisonous to much of the early life on earth.

One type of bacteria, cyanobacteria, produced oxygen as a sort of waste. At the time, very little free oxygen existed on planet Earth, but cyanobacteria changed that. The bacteria kept producing oxygen and eventually it poisoned the early Planet Earth, killing off most of the world’s lifeforms in the process. Luckily, evolution took hold and oxygen utilizing lifeforms came into existence.