I was getting all gloomy at the thought that classes resume in 6 weeks, but this cheered me right up: at least we’re not experiencing a Great Dying right now! Geologists have come up with a plausible explanation for the cause of the Permian extinction, 250 million years ago. Massive, prolonged volcanic eruptions in Siberia released clouds of halogens into the atmosphere that destroyed the ozone layer worldwide, having catastrophic effects on plant life.
Here’s an easy-to-digest video on the subject.
I don’t know about you, but awareness of our inevitable doom always makes me happy to live life in the moment. If it isn’t rocks falling from space, it’s our planet’s crust rupturing and spewing poisonous gases into the atmosphere, or permafrost melting and releasing ancient pathogens, or our own stupidity putting Donald Trump or Boris Johnson in charge. I think Ian Malcolm was wrong: the correct phrase is “Death will find a way.”
Awareness of our inevitable doom makes me thing about the future of my child.
PZ, do you ever think about the future of your grandchildren?
Much the same was going on during the last mass extinction, plus an asteroid impact.
The impact couldn’t have incinerated everything on the surface and boiled off the water, otherwise how would birds and frogs have managed to survive? A handful had parasols, issued by Wily Coyote?
The Big Six mass extinctions seem to be Murder on the Orient Express situations.
Keep in mind that in the late Permian, there had already been one pulse of extinction at the end of the Guadaloupian coincident with a sharp eustatic regression and the development of a large igneous province (LIP) in what is now southern China. There are other pulses of extinction as the PT boundary approached (though some of these may be erased through Signor-Lipps back smearing) which appear to be associated with sea-level changes without the influence of LIPs.
The Halon gasses certainly explain the massive die-off of plants on land. This can be clearly seen in the Karoo of South Africa where in a geologic instant, rivers ceased to meander and reverted to the braided streams of an environment with little or no plant life (see desert intermittent streams and streams in the arctic). However, there was also an extreme spike in temperatures (traceable through carbon isotopes, sulphur isotopes, and oxygen isotopes) which cannot be explained by the release of halon gasses. The most probable source for the heat spike was global warming caused by CO2.
One of the things that has given researches fits is finding a source for enough carbon to spike the temperature somewhere between 5C and 10C. Oxidation of the coal measures through which the Siberian eruptions moved and release of oceanic methane were definitely happening, but neither was enough to explain the spike. The best scenario for increased CO2 comes from the end-Guadaloupian events in southern China in which the LIP traveled through carbonaceous formations which were metamorphosed and, in the process, released billions of tons of carbon. This probably happened in Siberia to an even greater extent.
The eruption of the Siberian Traps released the halon gasses which decimated plant life (and, by extension, animal life on land). Additionally, SO2 created acid rain (evidence for this can be seen in elevated continental weathering as measured using strontium isotope ratios). CO2 emissions (evidence for this can be seen in the massive negative swing of 13C values) created global warming. The combination of global warming and increased CO2 levels contributed to oceanic stagnation and anoxia. And all this happened during a sea-level regression which had already stressed both land vertebrates (reduction and fragmentation of coastal habitat). The combination of ozone destruction, eustatic regression, acid rain, and global warming came damn near to wiping out life on land and left a landscape and seascape inhabited by only a few disaster taxa (Claraia in the oceans, Lystrosaurus on land).
This can be tested by looking at other LIPs events during the Mesozoic. Numerous LIPs occur throughout the Mesozoic, some with extinction rates elevated above background, but not enough to count as a major mass extinction event. Only two LIPs – end Triassic and end-Cretaceous – are associated with regression, and only one – end Cretaceous – is associated with regression and an additional stressor: the bolide impact at Chicxulub on the Yucatan.
The halon gas idea has been around for more than a decade (both Benton and Erwin explored this in their books When Life Nearly Died: The Greatest Mass Extinction of All Time (Benton, 2005) and Extinction: How Life on Earth Nearly Ended 250 Million Years Ago (Erwin, 2006). Wignall’s The Worst of Times: How Life on Earth Survived Eighty Million Years of Extinctions (Wignall, 2015) brings together the disparate threads which Erwin and Benton explore and shows the link between LIPs and extinctions, and the link between LIPs coupled with other stressors and mass extinctions. And these are the popular publications, not the peer-reviewed papers which came much earlier.
(sorry for the wall of text. this is one of the few areas in which I am well-versed. I am just confused as to why the halon component is given absolute priority and why this is considered new.)
Or Bolsonaro, who is busy as a bee shoving the Amazon rainforest over the tipping point of no return. He’s on track wrap that up in about 15 years.
Oggie @3: Wouldn’t a catastrophic die-off of the world’s plants also produce a spike in atmospheric CO2 levels? Or was it too extreme for that?
Some months ago my wife ran across a story about an app called WeCroak. I soon learned that several friends at work had picked it up. It’s premise: “In Bhutan they say contemplating death five times daily brings happiness.” I don’t know if Bhutan has such a saying (tho Bhutan prayer flags come in sets of five), but the contemplation in the case of WeCroak is spurred by quote. Several times a day I get a notice and a quote…some aren’t interesting, of course, but some are thought provoking. Like this one attributed to Mark Twain: “I do not fear death. I had been dead for billions and billions of years before I was born, and had not suffered the slightest inconvenience from it.”
For the future of this planet “There is no planet B” is a must read.
microraptor @5:
The way I understand it, most of the carbon within the plants was transported to the oceans which, as an unpleasant side effect, increased the carbon content of the ocean contributing to ocean anoxia. Some was also consumed, or at least used by, fungi.
Only six? You may want to look up “Holocene Extinction Event,” also known as the Anthropogenic Extinction Event.
I think I’d rather we were currently experiencing The Big Dying, instead of anthropogenic climate change, Trump, and all the rest of the crap that’s currently ruining the world. Sure, I probably wouldn’t live long, but as a guy who just LOVES volcanoes (I’ve climbed/hiked on 15 active volcanoes, 8 of which were erupting at the time), ‘twould be worth it. As the (possibly apocryphal) quote from poet Charles Bukowski says: “Find what you love, and let it kill you.”
Sounds good to me.