The asteroid that wiped out the dinosaurs 66 million years ago triggered one of the worst cases of climate change the world has ever seen.
Following the cataclysmic asteroid impact, the planet endured a period of global warming that lasted for 100,000 years.
Known as the Chicxulub asteroid, the collision released billions of tons of carbon dioxide into the atmosphere, which caused the temperature of the Earth to increase by five degrees Celsius (nine degrees Fahrenheit).
Researchers believe that understanding how the Earth reacted to severe global warming 66 million years ago could better equip them to deal with the ongoing climate change crisis.
The asteroid that wiped out the dinosaurs 66 million years ago triggered one of the worst cases of climate change the world has ever known. Following the impact, a period of global warming ensued — and lasted for 100,000 years (artist’s impression)
With a diameter between six to nine miles (seven to 14 kilometres), the meteorite smashed into the Yucatan Peninsula, in Mexico, where the town of Chicxulub is found today.
The impact left behind a 125-mile-wide (200 kilometre) crater and triggered the mass extinction of 75 per cent of all life on Earth.
After the meteorite hit, the planet was rocked by tsunamis and wildfires, swiftly followed by clouds of sulphurous gas that engulfed the planet for decades.
The carbon dioxide in the atmosphere caused the Earth to heat-up.
Theories on how the planet was able to rebound from this level of devastation vary.
Paleogeologist Ken MacLeod of the University of Missouri in Columbia tried to shed some light on the issue by studying tiny fish fossils — measuring about the size of a grain of sand — found in Tunisia.
‘We thought that we could resolve this question by looking at fossilised bits of fish teeth, scales and bones from the El Kef section in Tunisia,’ Dr MacLeod told Space.com.
WHY DID THE DINOSAURS GO EXTINCT?
Dinosaurs ruled and dominated Earth around 66 million years ago, before they suddenly went extinct.
The Cretaceous-Tertiary extinction event is the name given to this mass extinction.
It was believed for many years that the changing climate destroyed the food chain of the huge reptiles.
In the 1980’s, archaeologists discovered a layer of iridium.
This is an element that is rare on Earth but is found in vast quantities in space.
When this was dated, it coincided precisely with when the dinosaurs disappeared from the fossil record.
A decade later, scientists uncovered the massive Chicxulub Crater at the tip of Mexico’s Yucatán Peninsula, which dates to the period in question.
Scientific consensus now says that these two factors are linked and they were both probably caused by an enormous asteroid crashing to Earth.
With the projected size and impact velocity, the collision would have caused an enormous shock-wave and likely triggered seismic activity.
The fallout would have created plumes of ash that likely covered all of the planet and made it impossible for dinosaurs to survive.
Other animals and plant species had a shorter time-span between generations which allowed them to survive.
There are several other theories as to what caused the demise of the famous animals.
One early theory was that small mammals ate dinosaur eggs and another proposes that toxic angiosperms (flowering plants) killed them off.
‘This place is known for having a beautiful record across the interval that we are looking at — the so-called Cretaceous-Paleogene boundary — the mass extinction event following the Chicxulub impact.’
Dr MacLeod and his team were interested in the concentrations of different oxygen isotopes found in the fish fossils.
Signatures of isotopic oxygen inside fossils act like a thermometer, storing a record of the global temperature at the time the animal lived.
Researchers believe that understanding how the Earth reacted to severe global warming 66 million years ago could better equip them to deal with the ongoing climate change crisis
Dr MacLeod explained: ‘We are measuring the ratio of oxygen 16 to oxygen 18.
‘Every 1 part per 1,000 that the ratio changes correlates to an about 4.5- to 5-degree [C, or 8.1 to 9 degrees F] change in temperature.’
The researchers studied 40 samples in total: Ten were from the 50,000-year period before the asteroid impact, 20 samples were taken from the 100,000 years following the meteorite, and an additional ten samples from the subsequent 200,0000 years.
‘We found that there was a really big difference in oxygen isotopes between these three sets of samples — unambiguous,’ said Dr MacLeod.
The researchers are now hoping to study fossil samples from other parts of the world to check for similar results to those observed in Tunisia.
He said: ‘It’s one thing to find five degrees Celsius (nine degrees Fahrenheit) of warming in North Africa.
‘It’s even more impressive to find five degrees of warming in North Africa and perhaps 10 degrees Celsius (18 degrees Fahrenheit) of warming off the coast of Australia.
‘That would really strengthen the idea that it’s a global signal and a greenhouse gas-related change.’
According to MacLeod, these findings not only shed new light on the turmoil on Earth after the asteroid impact, but also raise questions about the consequences of current greenhouse gas emission levels.
Dr MacLeod cautioned: ‘If I were to draw a line under the lessons of this study for the modern era, it would be to contemplate the idea that what we are doing in our lifetimes will affect the Earth for the next 100,000 years, which is pretty daunting.’
The research was published in the journal Science.
WHEN WERE EARTH’S ‘BIG FIVE’ EXTINCTION EVENTS?
Traditionally, scientists have referred to the ‘Big Five’ mass extinctions, including perhaps the most famous mass extinction triggered by a meteorite impact that brought about the end of the dinosaurs 66 million years ago.
But the other major mass extinctions were caused by phenomena originating entirely on Earth, and while they are less well known, we may learn something from exploring them that could shed light on our current environmental crises.
- The Late Ordovician: This ancient crisis around 445m years ago saw two major waves of extinction, both caused by climate change associated with the advance and retreat of ice sheets in the southern hemisphere. This makes it the only major extinction to be linked to global cooling.
- The Late Devonian: This period is now regarded as a number of ‘pulses’ of extinction spread over 20m years, beginning 380m years ago. This extinction has been linked to major climate change, possibly caused by an eruption of the volcanic Viluy Traps area in modern-day Siberia. A major eruption might have caused rapid fluctations in sea levels and reduced oxygen levels in the oceans.
- The Middle Permian: Scientists have recently discovered another event 262m years ago that rivals the ‘Big Five’ in size. This event coincided with the Emeishan eruption in what’s now China, and is known to have caused simultaneous extinctions in the tropics and higher latitudes.
- The Late Permian: The Late Permian mass extinction around 252m years ago dwarfs all the other events, with about 96% of species becoming extinct. The extinction was triggered by a vast eruption of the Siberian Traps, a gigantic and prolonged volcanic event that covered much of modern day Siberia, which led to a cascade of environmental effects.
- The Late Triassic: The Late Triassic event, 201m years ago, shares a number of similarities with the Late Permian event. It was caused by another large-scale eruption, this time of the Central Atlantic Magmatic Province, which heralded the splitting of the supercontinent Pangaea and the initial opening of what would later become the Atlantic Ocean.