Nav: Home

Do volcanoes or an asteroid deserve blame for dinosaur extinction?

February 21, 2019

Based on new data published today in the journal Science, it seems increasingly likely that an asteroid or comet impact 66 million years ago reignited massive volcanic eruptions in India, half a world away from the impact site in the Caribbean Sea.

But it leaves unclear to what degree the two catastrophes contributed to the near-simultaneous mass extinction that killed off the dinosaurs and many other forms of life.

The research sheds light on huge lava flows that have erupted periodically over Earth's history, and how they have affected the atmosphere and altered the course of life on the planet.

In the study, University of California, Berkeley, scientists report the most precise and accurate dates yet for the intense volcanic eruptions in India that coincided with the worldwide extinction at the end of the Cretaceous Period, the so-called K-Pg boundary. The million-year sequence of eruptions spewed lava flows for distances of at least 500 kilometers across the Indian continent, creating the so-called Deccan Traps flood basalts that in some places are nearly 2 kilometers thick.

"Now that we have dated Deccan Traps lava flows in more and different locations, we see that the transition seems to be the same everywhere. I would say, with pretty high confidence, that the eruptions occurred within 50,000 years, and maybe 30,000 years, of the impact, which means they were synchronous within the margin of error," said Paul Renne, a professor-in-residence of earth and planetary science at UC Berkeley, director of the Berkeley Geochronology Center and senior author of the study, which will appear online Feb. 21. "That is an important validation of the hypothesis that the impact renewed lava flows."

The new dates also confirm earlier estimates that the lava flows continued for about a million years, but contain a surprise: three-quarters of the lava erupted after the impact. Previous studies suggested that about 80 percent of the lava erupted before the impact.

If most of the Deccan Traps lava had erupted before the impact, then gases emitted during the eruptions could have been the cause of global warming within the last 400,000 years of the Cretaceous Period, during which temperatures increased, on average, about 8 degrees Celsius (14.4 degrees Fahrenheit). During this period of warming, species would have evolved suited to hothouse conditions, only to be confronted by global cooling from the dust or by climate cooling gases caused by either the impact or the volcanos.

The cold would have been a shock from which most creatures would never have recovered, disappearing entirely from the fossil record: literally, a mass extinction.

But if most of the Deccan Traps lava emerged after the impact, this scenario needs rethinking.

"This changes our perspective on the role of the Deccan Traps in the K-Pg extinction," said first author Courtney Sprain, a former UC Berkeley doctoral student who is now a postdoc at the University of Liverpool in the United Kingdom. "Either the Deccan eruptions did not play a role - which we think unlikely - or a lot of climate-modifying gases were erupted during the lowest volume pulse of the eruptions."

The hypothesis that climate-altering volcanic gases leak out of underground magma chambers frequently, and not just during eruptions, is supported by evidence from present-day volcanos, such as those of the gas-spewing Mt. Etna in Italy and Popocatepetl in Mexico, the researchers said. Magma stewing below the surface is known to transmit gases to the atmosphere, even without eruptions.

"We are suggesting that it is very likely that a lot of the gases that come from magma systems precede eruptions; they don't necessarily correlate with eruptions," Renne said. In the case of the K-Pg extinction, the symptoms of significant climate change occurred before the peak in volcanic eruptions.

Flood basalts

Renne, Sprain and their colleagues are using a precise dating method, argon-argon dating, to determine when the impact occurred and when the Deccan Traps erupted to clarify the sequence of catastrophes at the end of the Cretaceous Period and beginning of the Tertiary Period - the K-Pg boundary, formerly referred to as the K-T boundary.

In 2013, using rocks from Montana, they obtained the most precise date yet for the impact, and in 2018, they updated that to 66,052,000 years ago, give or take 8,000 years. Then, in 2015, they determined from a handful of samples in India that, in at least one spot, the peak of the Deccan Traps eruptions occurred within about 50,000 years of that date, which means, in geologic time, that the incidents were basically simultaneous.

Now, with three times more rock samples from areas covering more of the Deccan Traps, the researchers have established that the time of peak eruptions was the same across much of the Indian continent. This supports the group's hypothesis that the asteroid impact triggered super-earthquakes that caused a strong burst of volcanism in India, which is almost directly opposite the impact site, the Chicxulub crater in the Caribbean Sea.

Sprain and Renne argue that the coincident catastrophes likely delivered a one-two punch to life on Earth, but the details are unclear. Volcanic eruptions produce lots of gases, but some, like carbon dioxide and methane, warm the planet, while others, like sulfur aerosols, are cooling. The impact itself would have sent dust into the atmosphere that blocked sunlight and cooled the Earth, though no one knows for how long.

"Both the impact and Deccan volcanism can produce similar environmental effects, but these are occurring on vastly differing timescales," Sprain said. "Therefore, to understand how each agent contributed to the extinction event, assessing timing is key."

Which gases in the Deccan Traps are emitted when is a question that's hard to answer, because there are no flood basalt eruptions going on today, despite numerous ones in Earth's history. The most recent, near the Columbia River in the Pacific Northwest, dwindled 15 million years ago after 400,000 years of eruptions.

The paucity of information about flood basalts is one reason Renne and Sprain are interested in the Deccan Traps, which are still young enough to contain information about the sequence, effects and scale of the eruptions, and perhaps the cause.

"It makes we wonder whether we may see some external forcing mechanism, like the impact for the Deccan Traps, for other flood basalts that lead up to major peaks in eruptions, like the Columbia River basalts or the Siberian Traps," Renne said. "Could a major earthquake in nearby subduction zones or the accumulation of pressure due to rising magma unleash these major episodes in flood basalts?"

Sprain noted that, in the same issue of Science, a research group at Princeton University also will publish new dates related to the Deccan Traps, some of which differ from those of the Berkeley group. Whereas the Berkeley group dated the mineral plagioclase from the actual lava flows, the Princeton group dated zircons in the sediment deposited between flows. Because it's unclear where the zircons came from, however, those dates provide only a maximum age for the lava, she said.
-end-
Other co-authors of the paper are volcanologist Stephen Self and graduate student Tushar Mittal of UC Berkeley, Loÿc Vanderkluysen of Drexel University in Philadelphia, Pennsylvania, and Kanchan Pande of the Indian Institute of Technology Bombay in Mumbai, India. The work was funded by the Ann and Gordon Getty Foundation, UC Berkeley's Esper S. Larsen Fund, Heising-Simons Foundation, National Science Foundation (EAR-1615021, EAR-1615203 and EAR-1615003) and Berkeley Geochronology Center.

University of California - Berkeley

Related Volcanic Eruptions Articles:

'Crystal clocks' used to time magma storage before volcanic eruptions
The molten rock that feeds volcanoes can be stored in the Earth's crust for as long as a thousand years, a result which may help with volcanic hazard management and better forecasting of when eruptions might occur.
Super volcanic eruptions interrupt ozone recovery
Strong volcanic eruptions, especially when a super volcano erupts, will have a strong impact on ozone, and might interrupt the ozone recovery processes.
Rare volcanic rocks lift lid on dangers of little-studied eruptions
Unusual rocks discovered on a remote mountainside have alerted scientists to the dangers posed by a little-studied type of volcano.
Revising the history of big, climate-altering volcanic eruptions
Researchers have developed a new isotopic method to analyze the recent history of large stratospheric volcanic eruptions, using 2,600 years' worth of records contained in ice cores from Antarctica. Stratospheric eruptions can launch sulfate particles more than 6 miles above Earth's surface, where they reflect sunlight and temporarily cool the planet.
Smaller, more frequent eruptions affect volcanic flare-ups
Eruption patterns in a New Zealand volcanic system reveal how the movement of magma rising through the crust leads to smaller, more frequent eruptions.
Using artificial intelligence to understand volcanic eruptions from tiny ash
Scientists led by Daigo Shoji from the Earth-Life Science Institute (Tokyo Institute of Technology) have shown that an artificial intelligence program called a Convolutional Neural Network can be trained to categorize volcanic ash particle shapes.
Repeating seismic events offer clues about Costa Rican volcanic eruptions
Repeating seismic events--events that have the same frequency content and waveform shapes--may offer a glimpse at the movement of magma and volcanic gases underneath Turrialba and Poas, two well-known active volcanoes in Costa Rica.
Detecting volcanic eruptions
Geophysicist Robin Matoza leads a case study of an eruption of Calbuco in Chile to evaluate data delivered by infrasound sensors
Mars' oceans formed early, possibly aided by massive volcanic eruptions
A new theory about how oceans and volcanoes interacted during the early history of Mars supports the idea that liquid water was once abundant and may still exist underground.
New insight into how magma feeds volcanic eruptions
A novel research study by scientists at the University of Liverpool has provided new insights into how molten rock (magma) moves through the Earth's crust to feed volcanic eruptions.
More Volcanic Eruptions News and Volcanic Eruptions Current Events

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Rethinking Anger
Anger is universal and complex: it can be quiet, festering, justified, vengeful, and destructive. This hour, TED speakers explore the many sides of anger, why we need it, and who's allowed to feel it. Guests include psychologists Ryan Martin and Russell Kolts, writer Soraya Chemaly, former talk radio host Lisa Fritsch, and business professor Dan Moshavi.
Now Playing: Science for the People

#538 Nobels and Astrophysics
This week we start with this year's physics Nobel Prize awarded to Jim Peebles, Michel Mayor, and Didier Queloz and finish with a discussion of the Nobel Prizes as a way to award and highlight important science. Are they still relevant? When science breakthroughs are built on the backs of hundreds -- and sometimes thousands -- of people's hard work, how do you pick just three to highlight? Join host Rachelle Saunders and astrophysicist, author, and science communicator Ethan Siegel for their chat about astrophysics and Nobel Prizes.