Whenever I fly across the Atlantic in daylight, I look out for Manicouagan Reservoir - so far, without luck. My interest in it is undiminished by it being dethroned as the putative cause of the Triassic-Jurassic extinction.
I could, though that might be too close up to appreciate what I hope will come across as its awesome majesty.
The article is also something of a cautionary tale against attempting it solo. I see that the author says "I didn’t see so much as a vapour trail in the sky", which is in line with my personal experience.
I have, however, seen Mont Mégantic from the air, which is pretty impressive in a way that probably cannot be fully appreciated from the ground - it looked to me rather like an upturned cup on a saucer, embedded at a shallow angle in the ground.
>So, this event could have put huge amounts of carbon dioxide into the air, causing an intense bout of global warming.
This leap at the end of the article is strange and comes with zero scientific backup. As far as the studies I’ve read, volcanic CO2 emissions are not large enough to cause greenhouse effects. SO2 and particulate emissions would actually create more of a cooling effect.
First off, SO2 breaks down quickly on geologic timescales. The cooling effect is short-lived. CO2 takes longer to move out of the atmosphere.
Next, modern day volcanic emissions aren't major players in current climatic changes, but that's not the case for the past. Large igneous provinces can dramatically alter global climate. CAMP magmatism was extremely widespread and prolific. You don't see the bulk of it at the surface, but large swaths of the eastern US coast and NW African coast are sitting on top of gigantic piles of basalt.
However, it's not _only_ CO2 for these large magmatic events. You're also dramatically altering ocean basins. Large igneous provinces are most frequently produced as continents break up. When that happens, you get a new ocean basin, change circulation, split things apart, introduce new species, raise/lower global sea level (ocean basin shape changes), and generally do a whole lot to shake things up. Continents can break up without much magmatic activity as well, but when you have mantle plumes involved in continental breakup, you tend to get the double-whammy of changes in ocean shape + lots of volcanic activity over huge areas. The extinction at ~200Ma (end of the Triassic, though the round number is a concidence) is a great example of magmatic activity having a large effect, but don't forget the impact that changing ocean basin shape/volume has as well.
Mass extinctions usually aren't things with single causes. Instead, they're generally the result of a lot of things combining.
Folks focus on the impact as the single cause of the K-T extinction, and while there's not doubt that it's what pushed things over the edge, other changes that had been ongoing for millions of years before had already stressed many different global ecosystems. You had major changes in volcanism (another large igneous province occurring during continental breakup, though it's smaller), reconfiguration of ocean basins, and other things occurring at the same time. The timing makes it clear that the impact was the sudden shock, but things were already heavily shaken up before that.
SO2 does break down within years to co2 and h2o, but if the volcanoes keep spewing the supply keeps getting replenished. There are periods in Earth's history where volcanoes are far more active and continuously so. So not really an open and shut case.
CO2 emissions during flood basalts can be enormous. One estimate I recall from the P-T boundary had CO2 levels going up to as much as 32,000 ppm. Carbon isotopes go crazy there. Granted, the magma of the Siberian Traps intruded right into the middle of a sedimentary basin containing enormous quantities of fossil carbon.
The cooling effect from SOx and particulates is short lived compared to CO2's warming. Also, heating in the stratosphere from particulates can, if bad enough, cause destruction of the ozone layer.
>> The cooling effect from SOx and particulates is short lived compared to CO2's warming.
Sure, but there's also the direct "making things die" effect of SOx. For humans this happens at much lower concentration than CO2, but I can't speak to dinotoxicity.
Volcanic activity is also the prime suspect in the Permian extinction, I don’t think the author’s statement is out of line. It’s conjecture anyway because the details are murky.
I remember having this theory explained to me once; let’s see if I can get it right.
The theorized asteroid hits some land mass on Earth and the impact causes a column of dirt to rise into the atmosphere and ultimately out of the atmosphere, at least to some degree. (As I understand it, the effect is similar to a column of water which replaces the vacuum left by a dropped object; fill a bowl with water and drop a marble in it to see a small-scale version.)
The column of dirt doesn’t manage to escape Earth’s gravity so it starts to fall back. The dirt this entire time is colliding with a whole bunch of air particles causing a lot of heat to be generated. This heat becomes enough to temporarily (hours) turn the surface of the Earth into an oven, which kills most life. A distant human-evolutionary ancestor had been a mammal which liked to burrow and the insulation provided by the surrounding dirt protected such animals from the heat.
I’m not sure about some details like I’m pretty sure (as theorized) the dirt might turn to glass as it goes up but I’m not sure how much that matters. The important things are the oven-like heat and how our ancestors were spared.
The energy of the asteroid is effectively turned into heat by the planet, which eventually dissipates but hypothetically not before cooking a lot of things.
You at least tried to explain the scenario. However, I don't believe that the volume of dirt and rock expelled by the impact is enough to engulf the entire planet.
It could cause heavy local damage. But it can't cause global extinction, unless the volume of dirt is the size of a continent.
> You at least tried to explain the scenario. However, I don't believe that the volume of dirt and rock expelled by the impact is enough to engulf the entire planet.
Have you done the math, or is this based on a gut feeling?
Because the people who have done the math disagree with you. Some of the ejecta would be thrown well out of the earth's gravitational pull, the other would end up various suborbital trajectories, coming down over the next day or so across the entire surface of the earth. Their re-entry heating will be enough to turn the entire sky incandescent, and the radiative heating will essentially barbecue the entire surface of the earth. Only swimming, burrowing or cave-dwelling animals would survive.
Also it depends on whose gut the feeling belongs to. To mine it doesn't sound so preposterous that an object falling from space at a huge velocities can cause ejecta which also flies up at huge velocities. Surely doing the math is the key for a proper answer but having a gut feeling can be a useful first order guide on a subject, as long as one remains open to further argumentation to further refine one's intuition.
As I understand, the plume of dirt then envelopes the planet with a blanket of dust, causing dramatic temperature reduction by blocking sunlight. Animals immediately dependent on food from the sun die very quickly, as the blanket of dust takes a very long time to dissipate.
There is also the possibility of increased volcanic activity due to disruption of the crust, depending on where it occurs and how large the impacting object is. That can exacerbate and prolong the blanketing of the earth, and introduce severe air quality issues as well.
I’m sure there are other challenges to life as well. It sounds like misery for decades.
I appreciate that you remain willing to engage in the subject. I’m not a physicist myself but I’ve been exposed to physical science enough to be wary of statements like this:
> It could cause heavy local damage. But it can't cause global extinction, unless the volume of dirt is the size of a continent.
If someone is going to make this claim academically, they will have calculated a whole bunch of things -- with perhaps some assumptions to numbers like mass, volume, velocity of the asteroid so they can play around with them as variables.
I will admit I have not dug deeper into this to find the numbers myself and do the relevant calculations. That is, in part, why I choose to be explicit about “theorized”. It’s what might have happened, given what we know, but it’s hard to be sure of what happened unless one studies the relevant ideas.
Assuming all energy went to the air, and you live in a nice place where the temperature is already 20°C(70°F) then the temperature increase to 40°C (100°F). That's bad, but you probably have time to jump into a lake if it's nearby (otherwise you are toasted).
This is mush less than an oven temperature like in the GP comment.
Almost none of the energy goes into the air. Air is barely heated by radiation, because it is transparent.
What happens is that the re-entry heating of the falling ejecta produces radiative heating, which directly heats the surface of the earth. And that gets cooked well past oven temperature.
The nice thing of energy conservation is that the details doesn't mater. So the energy of the radiative heating is less than the original energy of the meteorite that I estimated in 9.5E22 J. I guess it's much less, but it's a good upper bound.
The surface of the Earth is 5.1E14 m2, so it's 1.8E8 J/m2. I don't expect the fireworks to be synchronized so let's assume that they fall in an hour. That gets 50,000 W/m^2 For comparison, sunlight is 1,300 W/m^2 so it's almost like 40x sunlight. This bad, very bad.
I don't expect a 100% conversion of meteorite energy to fallout energy, but it's more dangerous that my initial calculation.
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I'm confused because the weight of the atmosphere is like the weight of 10m of water. So heating all the atmosphere is like heating a 10m layer of water. But actually water has a much bigger heat capacity, so the final temperature would be smaller. And dirt has an intermediate value. Also the radiation would not heat 10m of water or dirt, perhaps only the first meter.
So I expected that if my first calculation got a not dangerous temperature increase, I'd get in this second calculation a not dangerous result. So I guess I made a mistake in at least one of the calculations or my hand waving has a mistake.
I assume we have models for these dynamics. Anecdotally we recently had a couple wildfires in Canada that blanked a significant % of the US with smoke. You could drive through multiple states where the sun was partially blotted out.
The K-Pg impactor was larger than Mount Everest and the energy released in the impact was approximately 1000 times larger than the total combined nuclear arsenals of all countries.
What exactly is amusing? Large asteroids have the capability of introducing a sufficient large temporary disturbance of the worlds climate so that an extinction cascade might be triggered. It doesn't have to kill every single animal, just to disrupt enough food chains.
Which is exactly the worst-case with the current, human caused greenhouse effect.
You’re right that it always changes, but we don’t have record of it changing this quickly without it being caused by some traumatic geological event or something. We’re trending warmer way, way faster than evidence shows we normally do.
Nobody disputes that earth's climate changes naturally over time. People are arguing that human behavior (pollution) is causing climate change at a much faster pace than would otherwise occur.
Of course, as anyone who has a bit of scientific knowledge knows, it isn't a myth. It is an effect on top of the natural climate change caused by raising the CO2 content by 50%, mostly in the last 50 years. This causes a very quick warming at a speed far quicker than natural climate change. It is this speed which makes the climate change so dangerous. Which is where we are back at the asteroids. Beyond the direct impact damage, they cause a sudden climate shift.
3. That things heated by visible light radiate much of that heat back as infrared light?
4. That CO2 levels in the atmosphere are rapidly rising?
5. That raising CO2 levels will cause warming (see #1, #2, #3)?
6. That there are different isotopes of carbon, with different half lives?
7. That living things regularly exchange carbon with atmospheric carbon?
8. That because of that exchange the isotope ratios in carbon from living things matches the atmosphere carbon isotope ratios?
9. That when living things die they stop breathing?
10. That because of #6-10 we can tell from isotope ratios how long ago something died?
11. That as the CO2 levels have risen dramatically over the last couple hundred years, the isotope ratios of atmospheric carbon have changed?
12. That from these ratios we can tell that most of the increase in CO2 comes from sources that have not been exchanging carbon with the atmosphere for a very long time?
13. That fossil fuels come from long dead things, and have isotope ratios that match whatever provided most of that increased atmospheric CO2?
14. That the amount of CO2 that we are putting in the atmosphere from burning fossil fuels matches up closely with the amount of extra carbon we know must have come from sources that have not exchanged carbon with the atmosphere for a long time?
15. That we have satellites that can measure incoming and outgoing radiation and see that we are out of equilibrium, by an amount that fits with the amount that we would expect from that extra CO2?
If the climate change is caused by humans, that is more likely due to deforestation and destruction to nature.
CO2 is used by plants, and plants produce oxygen. If you kill more plants and build concrete cities over where they were...you could get your global warming.
Deforestation and destruction of nature could change CO2 levels, but they don't change the isotope mix of the carbon in atmospheric CO2. We know the increase is mostly coming from something whose carbon has a different isotope mix.
This isn’t really a good analogy because they usually kill by rupturing vital organs and/or make you eventually bleed to death. I think one can kinda make it work though. Expanding rounds from e.g assault rifles explode inside the body which is at least a little bit more akin to an asteroid that causes a lot of death through shockwaves and gusting winds rather than the mere local effect.
It's not the ball of rock and iron that is being killed, it's the ecosystems on its surface.
Ecosystems have "vital organs" as well. If you kill off enough key species they collapse. If you sufficiently change the environmental conditions to which all life is adapted, well then the majority of that life ceases to be able to live.
You are clearly here to argue, but who are you arguing against? Not the article I guess.
> For a while people thought this impact may have caused the Triassic-Jurassic mass extinction event. But now that the crater has been carefully dated, they don’t think that anymore. The extinction happened 12 million years later!
