FTV: Mass Extinction(s)
Let me be the first to admit that the above title isn’t exactly something designed to give you a warm and fuzzy feeling. It is a commonly held belief that the end of the dinosaur’s rule was the only time the Earth has undergone a mass sterilization of living things. The added ‘(s)’ is necessary because author Peter Brannen’s 2017 book The Ends of the World – Volcanic Apocalypses, Lethal Oceans, and Our Quest to Understand Earth’s Past Mass Extinctions (Harper Collins Books) points out the dinosaurs met their end in what would have been only the most recent mass extinction event. Brannen dug into the past and found throughout the eons of our planet’s history, there have been multiple times when various climatic and geological events have wiped the slate clean. That is the bad news. The good news is that our little corner of the universe seems to be quite resilient when it comes to rebounding after such cataclysmic events.
This FTV will not attempt to cover all of the episodes of mass extinctions Brannen covers because it would require me to reproduce the entire book. I was able to obtain a copy via Inter-Library loan from the Ontonagon Township Library after Todd at the WOAS-FM West Coast Bureau recommended it. If one has an interest in the entire story of these multiple mass extinction events, let me suggest you ask your friendly librarian to find Brannen’s book for you. We are going to narrow the focus here down to the aforementioned ‘dino killer’ event. Why? Even though this is probably one of the best known theories, geologists are still not in total agreement as to what exactly happened.
If the phrase ‘geologists are not in total agreement’ brings up a mental image of bespeckled men in white lab coats duking it out, let me punch some holes in that old stereotypical view of what a geologist (or any scientist) looks like. On one side of the ‘what did in the dinosaurs’ argument is a tenured geologist from Princeton named Gerta Keller. Keller did not come to the profession in any sort of usual way. She was born to a rural Swiss farm family. Brannen describes her as, “The youngest of twelve children and the black sheep of the family who repeatedly had her future ambitions thwarted. The first snub came as a teenager from a shrink who told her to abandon her hopes of becoming a doctor (because she came from too meager a background for such daydreams).” She fled the drudgery of an apprenticeship as a dressmaker and set off to see the world by hitchhiking across North Africa and the Middle East. “I’m a strange bird,” she admitted to Brannen. Sounds like she took a gap year before they were in vogue.
Her story would be offbeat enough as is, but it took a turn toward ‘stranger yet’ when she was preparing to take a trip on the trans-Siberian railroad. While she was taking care of a fellow traveler who became ill, she herself ended up ‘deathly ill’: “I got so sick I took a train to the Vienna hospital, where they thought it was a miracle still to be alive. I was isolated for six weeks on intravenous before checking myself out of the hospital. I have a habit of doing that.”
Her next episode off the beaten path took her to Australia: “I got shot in a bank robbery. I was pronounced dead.” Brannen says, “The bullet passed between her heart and spine, pierced her lungs, and shattered her ribs on the other side.” Brannen later describes Keller as having a ‘stubborn streak’. Did she become this way after all of this or was it part of it the reason why she refused to go quietly into the great beyond?
For some reason, Gerta had always thought she would die at the age of twenty-three. After getting shot at age twenty-two, she decided perhaps living longer wasn’t a bad option. She continued her story: “The entire blue sky was essentially a film of my life going by, and by the time I got to the end I said, ‘I don’t want to die,’ and that was it. I had this weird experience where I came to, and I was floating over Sydney. It was very peaceful. Then there was this ambulance and siren breaking the peace, making a big racket. I heard this woman scream and calling for her momma and I got really annoyed. I thought, ‘Jeez, I would never do that’. All of a sudden I was sucked down and I was the woman screaming, and there were two orderlies holding me down.” Brannen asked if she may have been hallucinating. Gerta said she later visited places she had seen in her Sydney fly by – places she had never been to before she was shot – and they were just as she remembered them.
After she recovered, Keller found herself living in a ghetto in San Francisco. Her academic life began as an adult high school student before she landed at San Francisco State long before she joined the Princeton faculty. Now that we have dispelled any notions you may have had about the stereotypical science nerd, we will set Gerta Keller aside for a few moments and get back to dinosaur extinction.
The causes for the end of the dinosaur’s reign has been debated ever since their bones were first dug up. Cartoonist Gary Larson’s The Far Side cartoons ventured various humorous ideas by showing dinosaurs smoking or arriving too late to board Noah’s Ark. Some theories were dismissed out of hand (and not very humorously) while others were tossed into the growing pool of ideas to sink or swim. The most widely accepted theory (the Alvarez Asteroid Impact Hypothesis) was first put forth by the father-son team of Luiz and Walter Alvarez. They were studying layers of clay found at what is known as the Cretaceous-Paleogene (K-PG or more popularly, the K-T) Boundary in Gubbio, Italy. Upon finding a layer of iridium embedded in the boundary layers before the dinosaurs went extinct, they reasoned they had been killed off by a massive asteroid strike. Iridium is rare on the Earth but commonly found in asteroids. The world-wide distribution of this iridium rich layer led to their Asteroid Impact Hypothesis. Naturally, the theory was greeted with skepticism and cries of, “Okay, show us the impact site and we will (maybe) believe you.” It remained controversial as long as they couldn’t find the smoking gun (or crater, in this case).
Here is a highly condensed version of what came next: The massive 110 mile diameter Chicxulub crater was discovered on the northeast coast of the Yucatan Peninsula in Mexico. The full story of the discovery can be found in Alvarez’s book T. rex and the Crater of Doom (1997). The impacting object was traveling so fast and was massive enough to punch through the Earth’s atmosphere and straight through the crust to the mantle below. Some of the material dislodged by the asteroid strike was hurled into space while the rest would have taken suborbital paths like a flock of ICBMs to the far reaches of the horizon. Theories on how high the temperatures rose in the atmosphere, how much damage the shockwave would have done, and how widely the tsunami created would have carried debris inland were tossed about. The details of such a strike are chilling, indeed, and one wonders how any life would have survived this hellish version of Earth.
Critics (of the Alvarez theory) pointed to a 62-mile-wide crater in Manicouagan, Quebec which is easily visible from the International Space Station. Some geologists pondered, “Why was there not a similar extinction event associated with a strike nearly as large as the Chicxulub impact?” Others, like Gerta Keller, simply pointed out inconsistencies in the ‘global annihilation by an asteroid strike’ theory. For example, the oxygen requirements of the global firestorm set off by the rain of asteroid ejecta doesn’t add up. Brennan interpreted the evidence of the asteroid strike as a killing mechanism as, “Dubious.” “Claims that the atmosphere was temporarily heated to the temperature of a pizza oven have long been viewed with skepticism by biologists,” is how Keller stated it. She favors an extinction event more aligned with global volcanism which puts her at odds with those leaning heavily toward the Asteroid Impact Hypothesis. The discussions from these opposite ends of this ‘who done it’ mystery have been, at times, heated.
Theories are ideas, however, and not always carved in stone. As new data is collected and new eyes are focused on the questions raised by supporters and skeptics, theories evolve. One of the things that haunted both the ‘asteroid vs volcanism’ theories was the time line. How close did the event occur to the actual extinction event? Drilling cores collected from deep layers of ancient ocean sediments and lava flows slowly began to narrow this gap. Whatever cataclysmic event caused the extinctions reflected in the K-T boundary rock layers caused further tweaks in both the Alvarez and Keller theories.
Keller’s volcanic hypothesis focused on an area in India known as the Deccan Traps. As the Indian subcontinent separated from the supercontinent known as Gondwana, it moved across a hotspot in the Earth’s mantle. Known as the ‘Reunion Hotspot’ (the volcanic island of Reunion is currently sitting on top of this stationary lava source), it traces an arc of islands by it that includes the Maldives, the Seychelles, and Mauritius. This island arc is very similar to the one that created the Hawaiian Island chain as continental drift moved that part of the Pacific Ocean crustal plate over another hotspot. When India itself passed over the Reunion Hotspot, it created lava flows (in some areas they are two miles thick) known as the Deccan Traps.
Geologists studying the Deccan Traps deposits in India’s western Mahabaleshwar district noticed something interesting as they sampled the layers making up these 11,500 foot tall mountains. The lower deposits show a great deal of fracturing and a chemical mix consistent with molten rock moving slowly toward the surface. This gave the magma time to melt the crustal rock and absorb the minerals into the lavas. The upper layers, however, were not fractured and do not display the mix of crustal elements found at greater depths. It looks as though a great amount of material gushed from the Earth’s mantle from the Reunion Hotspot. The later Deccan Flows were formed much faster than the earlier, lower layers.
UC Berkeley geologist Mark Richards has always favored the Alvarez camp. At an annual meeting of the Geological Society of America, he was scheduled to speak after Keller’s presentation. Richards’ talk was expected to be a rebuttal of the ‘Deccan deposit volcanism vs the Asteroid Impact Hypothesis’ address. Surprisingly, he began by acknowledging the topic as, “The 80 pound gorilla in the room that has turned into an 8,000 pound gorilla, in my view.” He went on to explain that new data shows the Chicxalub impact and the accretion of the Deccan Traps lava flows was just too close together for him to feel comfortable giving one or the other credit for being the mechanism that killed the dinosaurs. As he told the GSA gathering, “The chances of these [the impact and the lava flows] occurring at random seem to either imply some sort of casual effect or some kind of divine intervention. And since I am no expert on the latter – I am a geophysicist – I’m going to concentrate on what may have been considered an outrageous hypothesis a couple of years ago, which I no longer think is such an outrageous idea.”
Richards was inspired to reexamine his views by a middle of the night epiphany he had after visiting the Mayan ruins of Chichen Itza in the Yucatan Peninsula. He suddenly remembered reading about a theory that earthquakes have been proven to cause volcanic eruptions. Data collected had all but verified that the stronger an earthquake was, the further away it could cause increased volcanism. The estimated strength of the ground disturbance caused by the Chicxulub impact was an earthquake with an unbelievable magnitude of 11. Extrapolating this data from volcanic activity stimulated by earthquakes of a smaller magnitude, he decided that the dinosaur killing event was actually caused by a ‘one-two’ punch.
Yes, the asteroid impact hurled a massive amount of material into space and into the atmosphere. It also triggered a surge of volcanism from the already erupting Deccan Traps that, “Was like a fire hose right out of the mantle,” according to Richards. When Alvarez himself read Richards’ ideas, he personally called him on a Sunday afternoon and invited him to come over ‘right now’ to discuss it. Richards and Alvarez concluded, “[The new data] suggested that the Deccan Traps were yawning and maybe saying, ‘We’re done,’ . . . and then something happened.” The ‘something’ would have been the Chicxulub asteroid impact. The lower levels of the Deccan Trap flows just happen to rest on top of the K-T extinction boundary.
Richards’ work has begun to bring the two sides closer together but he has avoided blaming the death of the dinosaurs on one or the other (or both) events. “This has been an acrimonious debate,” he told Brannen, “I’ve been trying to steer clear of that. We’re going to find out in the next couple of years what happened, We might as well just all be friends and find out. Together. This story is only going to get more interesting.”
A colleague of Richards named Paul Renne is less reluctant to avoid embracing this new view of the K-T boundary extinction: “I think maybe we are moving away from fireballs and damnation and that sort of thing. It’s been a great mystery for many years. Bigger impacts have shown to be associated with flood basalts like the Deccan Traps – so why is this a bizarre coincidence? It may be that Chicxulub was the gun and the Deccan Traps were the bullet,” Renne said.
The Lake Superior Basin has a similar history to the Deccan Traps. At one point in our geological history, a series of fissures in our neighborhood pumped out lava flows in a volume never before seen. Unlike the area of India where the Deccan Traps were created, the lava flows created here caused the crust to sag under the weight of the new layers. The Lake Superior Traps are thousands of feet thick and their weight pushed the mantle below the crust down. This sag in the crust directed the advancing continental glaciers of the last Ice Age into the valley created by the sinking crust. When the glaciers melted back, they filled the deep valley gouged out of the Earth and it became (in stages) Lake Superior. Had this volcanic activity occurred around the time of another massive asteroid strike, maybe the Lake Superior region would get the blame for killing off the dinosaurs.
For the record, there have been five major extinction events on Earth, including the one that did in the dinosaurs. Some think humans will cause the sixth. Paleontologist Doug Erwin says, “If we have already started the sixth extinction, buy a case of Scotch because nothing will reverse it. I think if we keep things up long enough [meaning ‘human degradation of the Earth’s environment], we’ll get to a mass extinction, but we’re not in a mass extinction yet, and I think that’s an optimistic discovery because that means we actually have time to avoid Armageddon.”
Are we smart enough to not return to burning more coal, stop disavowing the value of wind and solar power, and dismantling the regulatory agencies designed to keep us from reaching such a tipping point? I, for one, sure hope we are.
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