Tag Archives: chicxulub

Meteorite and volcanoes may have worked together to wipe out dinosaurs

New evidence suggests that both a meteorite and massive volcano eruptions worked together to wipe out the dinosaurs.

An apocalyptic impact

Dinosaurs ruled the planet for over a hundred million years, but their reign came to an abrupt end some 66 million years ago, at the end of the Cretaceous. The most popular theory, and the one with the most evidence to back it is that this abrupt end was brought about by a massive asteroid or a comet — the crater of which we call Chicxulub.

The Chicxulub impact crater, as it can be “seen” through geophysical techniques.

Chicxulub lies underneath the Yucatán Peninsula in Mexico, hidden to the naked eye, visible only through geophysical techniques. The crater, which measures 150 kilometers (93 miles) in diameter and 20 km (12 mi) in depth, indicates an apocalyptic impact. Geologists estimate that the impact had the energy of 10 billion Hiroshima A-bombs, millions of times more powerful than any object mankind has ever detonated. Words can’t do this event justice.

A cloud of super-heated dust, ash and steam spread from the crater at dramatic speeds, as the impact body burrowed underground in less than a second. Virtually all life 5,000 km away was wiped instantly. But the worst was still yet to come.

The impact triggered a massive emission of dust and particles which covered the entire surface of the Earth for several years, possibly a decade, creating a harsh environment for living things. Initially, the shock destruction of carbonate rocks led to a sudden and powerful greenhouse effect, heating the planet. But as time went on, the dust particles blocked the sunlight from reaching the surface of the Earth, cooling the surface dramatically.

To top it all off, the impact generated ungodly shockwaves, which in turn caused earthquakes and caused volcanic activity. This is where the new study comes in.

A one-two punch

New oceanic crust is constantly produced at mid-oceanic ridges. Here, red represents the newer crust. This helps geologists get a ballpark figure for dating the rocks. The date is then finessed through direct measurement techniques.

As if all that wasn’t enough, the impact also triggered volcanic activity which helped seal the dinosaurs’ fate.

“We found evidence for a previously unknown period of globally heighted volcanic activity during the mass-extinction event,” said former UO doctoral student Joseph Byrnes.

Byrnes and Leif Karlstrom, a professor in the UO’s Department of Earth Sciences, analyzed a record of volcanism preserved along the mid-ocean ridges — underwater mountain system formed at the edge of tectonic plates.

In order to assess the volcanic activity, they used a geophysical technique called gravity surveying. This approach involves measuring the Earth’s gravitational field using highly sensitive instruments, capable of picking up even minute differences. In this instance, researchers used freely available satellite data.

By mapping the gravity field, they are able to deduct the density of the underlying rocks and thus, they have some information as to what kind of rock they’re looking at (for instance, a volcanic basalt will have a much higher density than a sedimentary limestone). This allows them to identify volcanic regions, and improved dating methods allowed them to place the increased volcanic activity right at the same time as Chicxulub, establishing a strong correlation.

“Our work suggests a connection between these exceedingly rare and catastrophic events, distributed over the entire planet,” Karlstrom said. “The meteorite’s impact may have influenced volcanic eruptions that were already going on, making for a one-two punch.”

So, researchers conclude, it wasn’t the impact itself that wiped out the dinosaurs, but rather a cascade of effects, including massive eruptions of underwater volcanoes. It’s another important reminder that the Earth is a tightly-knit ecosystem, and severe events tend to propagate all around the planet.

However, perhaps it’s important to note that through this catastrophe, and a few similarly devastating events, life still managed to find a way. Dinosaurs themselves, despite popular knowledge, are not exactly extinct. In a way, they’re thriving — as birds. A group of dinosaurs evolved and adapted, becoming the birds we see all around us.

Artistic depiction of the Chicxulub ipact. This painting by Donald E. Davis depicts an asteroid slamming into tropical, shallow seas of the sulfur-rich Yucatan Peninsula in what is today southeast Mexico.

Journal Reference: Joseph S. Byrnes, Leif Karlstrom. Anomalous K-Pg–aged seafloor attributed to impact-induced mid-ocean ridge magmatism.  DOI: 10.1126/sciadv.aao2994

Scientists zoom into Chicxulub, the “dinosaur crater”

Geologists are getting an unprecedented glimpse into the asteroid that wiped out the dinosaurs and much of life on Earth 65 million years ago.

Gravity anomaly map of the Chicxulub impact structure. The coastline is shown as a white line. Image by USGS.

When two geophysicists discovered a huge crater in the Yucatán Peninsula in Mexico in the late 70s, the entire geologic world was thrilled. The date of the crater coincided precisely with the Cretaceous–Paleogene boundary which marks the end of the Mesozoic. It also offered a great explanation to the massive extinction which occurred at that boundary. But for all the answers it offered, Chicxulub posed even more questions.

The crater is over 180 km (110 miles) in diameter, located next to the village of Chicxulub in Yucatan. We have a pretty good idea of the accuracy, as well as the diameter and the energy released. There’s also a strong case regarding the impact the meteorite impact had on life on Earth – it basically wiped out a large part of it. But how, exactly? Why did some creatures survive and others didn’t? How did life bounce back after it? And perhaps more importantly, what can we learn from it in regards to our current situation?

Those are all questions scientists would like to answer, but in order for that, they need to take core samples from the crater – and that’s deep underground, offshore. Chicxulub is the only known Earth crater with a remaining impact peak ring, but it is under 600 m (2,000 ft) of sediment. The drilling machine already pushed 1,335m below the modern sea floor and now, for the first time, researchers are getting real samples straight from the crater.

TIM PEAKE/NASA/ESA

“They’re very strange rocks,” explained Prof Jo Morgan, who is involved in the study. “The rocks have formed this feature: it’s called a ‘peak ring’. They’re very, very highly… what we call ‘shocked’. Shock pressures of many tens of gigapascals have deformed the rocks. They’re also highly fractured, and have moved long distances. So, even though they’re made of granite-type rocks, they’re amazingly different to anything else we see in the world.”

The international project has already acquired the hundreds of metres it drilled from beneath the Gulf floor earlier this year to the MARUM Center for Marine Environmental Sciences, at the University of Bremen, Germany. Rock analysis ios a long-term endeavor, but Prof Sean Gulick, from the University of Texas, US, one of the two chief scientists involved, has shared some of his initial thoughts:

“We’ve been able to examine that first 10,000 years after the impact, which is dominated by what we call ‘disaster species’ – dominated by the organisms that love stressed environments. And then we can see evolution coming back in [during] the next few hundred thousands years after that,” he told BBC News.

The ‘disaster species’ he’s referring to are basically small plankton invading the pore spaces and cracks in and around the crater. As they analyze more and more what happened after the impact, we’ll get a clearer picture of life’s re-emergence in the area.

“We’ve got some cell counts and some DNA, but it’s all very early days; we’re very concerned about contamination,” Prof Morgan added. “But the signs are that, yes, this crater was occupied soon after the impact.”

 

Scientists digging into the dinosaur-killing asteroid crater answer all your questions

A team of researchers is investigating the Chicxulub crater, of the asteroid that wiped the dinosaurs (and many other creatures) some 65,5 million years ago. Now, they’ve set out to Reddit to answer all our questions. Sean Gulick from the University of Texas Institute for Geophysics (UTIG) and Joanna Morgan from the Imperial College London as well as postdoctoral fellow Chris Lowery have been drilling in the crater since April 14 and will spend approximately two months at sea retrieving rock cores before returning to their respective institutions to study the samples. These are some of their most interesting answers.

Sketch of the gravity anomaly map of the Chicxulub crater area. Red and yellow are gravity highs, green and blue are gravity lows, white indicates sinkholes, or “cenotes”, and the shaded area is the Yucatan Peninsula. Image via NASA.

Firstly, a comment:

Not a direct reply to anyone’s question, but I’m just going to leave this here:

http://joidesresolution.org/sites/default/files/Blast%20from%20the%20Past%20Poster.pdf

It’s a little old (you’ll notice that they have the boundary at 65 when we now have it at 66 million years ago), but it’s probably my favorite poster because it shows 1) how the microfossils that I study, which are called foraminifera, changed across the boundary (~90% of the ones that live in the upper water column went extinct), and 2) what the KPg Boundary looks like in deep sea sites, in this case from ODP Leg 171B from off the Atlantic coast of Florida.

(Chris)

Then the questions:

Q:After the impact, how quickly (or slowly) did it kill the dinosaurs?
How did it kill them (most interested about those that didn’t die quickly)?
What other animal and plant life was lost?
How big of a percentage of animal and plant life was lost?

A: Depends where they were. Within about 1500 km from Chicxulub dinosaurs would have been killed instantaneously by thermal radiation, as this impact behaved a bit like a very very large atomic bomb. On the other side of the Earth it could have taken months, following the destruction of much of the primary food source due to fires, as well as dark and cold conditions. 90 % of the near-surface plankton in the oceans, ammonites… about 75% of life in total (Jo)

Q: How sure are you this was their extinction event and what’s the science behind it?

We are very sure that this impact caused the KPg mass extinction, which killed ~75% of all species on the planet, including non-avian dinosaurs, marine reptiles like mosasaurs and plesiosaurs, and other unique marine groups like ammonites. As thattopicishot mentioned a little while ago, we know this because of the unique layer of clay found at the top of Cretaceous sediments worldwide, which contains iridium (very rare on earth; very common in asteroids) and minerals that are formed in impacts like shocked quartz and glass spherules that were blasted out of the crater. We know that this clay comes from the Chicxulub crater very simply because this layer gets thicker the closer you get to the crater. In sites very far away (Europe, Japan, Australia) it’s just a thin layer of clay with iridium; as you get closer (North Atlantic) it gets thicker, with a clear layer of spherules and shocked quartz below a clay layer with iridium; in the Gulf of Mexico this boundary layer can be hundreds of meters thick, and large chunks of rock that were blasted from the crater, meters-thick layers of sand deposited by tsunamis that washed back and forth across the basin, and thin a clay layer with iridium on top.
More generally, we are so confident that this impact was the cause of the mass extinction because we clearly see all these groups range right up to the boundary.
(Chris)

Reddit’s user didn’t waste the opportunity to add some memes to the discussion:

Q: Will you take full responsibility if you awaken an ancient godlike monstrosity from beyond the stars from its timeless slumber?
And on a more serious note, what are you hoping to discover from this impact site? Why is it unique from others?

A: Full responsibility taken. We want to know: how large craters are formed, is there a deep biosphere, how did life recover in the ocean above the crater? It is the most intact large crater on Earth, the only crater with a peak ring, the only impact linked to a mass extinction and the only crater with a global ejecta layer (Jo)

Drawing of the Chicxulub crater, by Blogue Dementia Cratera Chicxulub

About actually intercepting the K-Pg layers, they said:

We reached the K-Pg boundary at 620 m and are now at 840 m. We hope to get down to 1500 m. We are testing models for peak ring and large crater formation, we think peak rings are formed by rocks that were pushed down 20-30 km, then rebounded upwards above the Earth surface, and collapsed downwards and outwards about 40 km. We are also taking microbiological samples to see if there is a living a deep biosphere, and looking to see how life recovers after the impact in the ocean above the crater? (Jo)

Q: Do you expect to find fragments of the impactor, or are you mainly interested in an analysis of the crater and subsequent layers?

A: About 95% of the meteor was vaporized on impact, and ejected all around the Earth in the expanding vapor plume. That’s how we discovered the impact occurred in the first place – we found the meteoritic material in the K-Pg boundary layer all around the Earth. We are mainly interested in other things, how are large craters formed, is there a deep biosphere, how did life recover in the ocean above the crater? (Jo)

Some questions were on point:

  • What is the magnitude of seismicity associated with the impact?
  • Everyone is very interested in the impacts effects on life and the K-Pg mass extinction, but what about tectonics?, I am interested what effect an impact of this size who have on plate kinematics, and if the Impact caused plate motions to change, or far field changes in deformation styles along plate boundaries.
  • How deep is the Crater, and by using paired thermochronometers is it possible to reconstruct the thermal/cooling history of the impact site? or will they likely be reset by later burial?
  • How is the age of impact constrained? I assume mostly by stratigraphic dating of the Iridium layer found around the world, But do you have any plans to directly date the Impact? is it possible to use zircons quenched during impact? also would those zircons/other minerals produced during impact have a distinct geochemical/isotopic signature?

Great questions: -Magnitude 12 or even 13 have been estimated such that all the continental shelves around the Gulf of Mexico collapsed due to the seismic energy -So its not thought that the impact changed anything in terms of tectonics over the long term, but the amount of energy released might have induced some seismicity on tectonic boundaries. -The crater when it initially formed was 100 km wide and ~30 km deep but it rapidly (within minutes) rebounded and collapsed such that the final crater floor of the much larger final crater(~200 km) was only ~1-1.5 km deep. We are definitely looking to use thermochronometers to study the history of the thermal effects and cooling. -Age of the impact is constrained through magnetic stratigraphy, biostratigraphy, and most recently thermochronology. In fact it defines the boundary in the geologic timescale between Mesozoic and Cenozoic. -Jousting in June in Indiana and in July in Germany :-)

Sean

Q: since the crater has been there for 66 million years, what made you suddenly decide to probe it now?
Thanks and good luck!

Well, for the first 65,999,953 years we didn’t have a scientific ocean drilling program, so really we got here as quickly as we could. (Chris)

Q: How controversial is the Chicxulub impact theory in your field? Or is it generally uncontested and accepted as a fact?

Good question on our certainty! In the geological community the impact hypotheses is by far the most supported and with the best evidence amongst the theories. It explains the truly sudden nature of the event and direct evidence is present in terms of the iridium anomaly precisely at the extinction event. If I had to put a number on it greater than 95% of our community is convinced of the scientific evidence that the Chicxulub impact was the cause of the end Cretaceous mass extinction event. If you know scientists then that is saying something! We would like use the word Theory to now describe this conclusion. -Sean

I think it’s pretty widely accepted. There’s a (vocal) group that has been flying the flag for various alternate hypotheses for a while, but most of the community is on board with the impact theory. This paper does a pretty good job explaining the evidence and why competing theories are probably wrong. I think it’s written at a pretty generalist level, but I have a PhD in this and so I’m probably not the best judge.

http://eesc.columbia.edu/courses/w4937/Readings/Schulte.etal.2010.pdf

(Chris)

Lastly, Reddit’s users posed another interesting question about the availability of the resulting data.

Q: Will there be any open hole logging done in addition to core recovery, and will this data be made publicly available?

Yes we are open hole logging each interval that is exposed before we then case and move on to greater depths. All of our data collected out here will be publicly available through the International Ocean Discovery Program after the moratorium ends. – Sean

Asteroid that wiped out the dinosaurs may have been a set of binary asteroids

The (still debated) asteroid that slammed into the Earth 65 million years ago and played a crucial role in wiping dinosaurs out, may have actually been a binary system- 2 asteroids engaged in an orbit around each other.

Double trouble

binary asteroid

The surprising claim comes from analyzing the proportion of asteroid craters on Earth that were formed from binary impacts; the results also add to the concern of those who fear catastrophic collisions in future. Here’s the deal: our planet bears the scars of twin-asteroid impacts just like single impact craters; a good example is the Clearwater Lakes near Hudson Bay in Canada, formed 290 million years ago. However, examples like this are pretty rare: 98% of all craters are single impact, with only 2 in 100 coming from a binary system.

“It’s been known for 15 years that about 15 per cent of near-Earth asteroids are binary,” says Katarina Miljković at the Institute of Earth Physics in Paris, France.

So, all things being equal, if 15 percent of all asteroids are binary, why aren’t 15 percent of craters binary ? Miljković and her colleagues believe they have found the answer: they ran computer simulations and found that even binary systems often form a single crater, mimicking a single asteroid impact.

Considering that the crater is typically 10 times bigger than the asteroid, this seems intuitive. The team found that only unusual cases involving two small, widely separated asteroids are guaranteed to form a pair of distinct craters. Their simulations confirmed that such situations are just rare enough to explain why paired craters account for only 2 per cent of all Earth’s craters.

Symmetry and non-symmetry

crater_c

The next step was, of course, seeing if single craters caused by single asteroids could be differentiated by single craters caused by binary asteroids. What they found is that it is possible to identify which of Earth’s single craters had binary origins – these craters should be subtly asymmetrical – a feature displayed by the crater near Chicxulub in Mexico – thought to lead to the extinction of the dinosaurs.

“The Chicxulub crater shows some important asymmetries,” says Miljković. “It is worth considering that it was formed by a binary asteroid.”

Geophysical research is key to studying such impact craters – gravity measurements are a great indication for this, especially for asteroids which are still buried. Studying the gravity anomalies supported this theory, as Petr Pravec at the Academy of Sciences of the Czech Republic in Ondrejov explained.

“The signatures also suggested that the Chicxulub crater might have been formed by a binary asteroid impact,” he says.

So what did Chicxulub looked like? Most likely, if it was indeed a binary, the 180 km radius of the crater suggests the combined diameter of the two asteroids being somewhere around 7 to 10 km – the same diameter as the single rock previously imagined to be the culprit.

Twice the asteroid – twice the problem?

If this is true, what does it mean for future impact mitigation and preparation? Even with today’s technology, we have what it takes to totally avoid the dangers posed by an asteroid, but what happens with a binary?

“I am not sure if any of the proposed asteroid deflection techniques could deflect both binary components with a single weapon,” says Katarina Miljković at the Institute of Earth Physics in Paris, France, who led the new study.

However, researchers seem prepared for this possibility as well. Don Yeomans of NASA’s Near Earth Object Program thinks that won’t be a problem for a future asteroid-deflecting spacecraft.

“There is a slim chance that the autonomous navigation camera might be confused with two images in its field of view, but I should think these issues would be easily overcome,” he says.

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