Kurzgesagt – In a Nutshell
Kurzgesagt – In a Nutshell
Embedded Files
Sources - What actually killed the dinos?
Sources - What actually killed the dinos?
We thank the following experts for their critical reading and input:
Prof. Blair Schoene
Department of Geosciences, Princeton University
Prof. Stephen Brusatte
Professor of Palaeontology and Evolution, University of Edinburgh
The Last Days of a Kingdom
- It was the last days of the Cretaceous, one of the hottest periods in Earth’s history and much more humid. Lush jungles and woodlands covered much of the planet. Even the polar regions were home to forests of prehistoric pines and ferns.
Globally, the average temperature (“global average temperate” or “GAT”), of the earth's surface is 15°C. In the Cretaceous, that means 145 to 66 million years ago, the temperature was sometimes above 20°C. These periods are sometimes referred to as the "hothouse".
#Scotese, C. R. et al. (2021): Phanerozoic paleotemperatures: The earth’s changing climate during the last 540 million years. Earth-Science Revies, Vol. 215
https://www.sciencedirect.com/science/article/abs/pii/S0012825221000027
Quote: “If one imagines where the current phase of anthropogenic global warming is heading, one immediately thinks of the hothouse worlds of the Late Cretaceous and Eocene (Huber, 1998; Huber et al., 2000). During the Mid Cretaceous – Paleogene Hothouse global temperatures were indeedmuch warmer than the present-day (GAT = 28°C during the Late Cretaceous versus GAT = 15°C for the Modern). It remains to be seen whether we will succeed in warming the Earth to that degree, but at least we now know what a warmer world would look like.
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There are also have been times when there was no ice above the polar circle – even during the winter (e.g., Late Cretaceous, Fig. 4). During these “hothouse” times, the average temperature of the Earth was generally above 20°C (68°F) and the polar regions were relatively warm (5°C to 15°C) and no ice could accumulate. It is a well-established fact that no polar ice existed during the Paleocene-Eocene Thermal Maximum (55.6 Ma, McInerney and Wing, 2011 ) or the CenomanianTuronian Thermal Maximum (93 Ma, Ziegler et al., 1985).”
Figure 2 shows a map of the paleovegetation for the Maastrichtian, i.e. the upper circles (approx. 77 to 66 million years ago. The polar regions consisted of "polar deciduous forest" (blue-green color), some of which was evergreen.
#Upchurch Jr., G.R. et al. (2007): Paleobotanical Evidence for Climatic Change across the Cretaceous-Tertiary Boundary, North America: Twenty Years after Wolfe and Upchurch. CFS Courier Forschungsinstitut Senckenberg, Vol. 15 (258)
#Beerling, D.J. & Osborne, C.P. (2002): Physiological Ecology of Mesozoic Polar Forests in a High CO2 Environmen. Annals of Botany, Vol. 89 (3)
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4233824/
Quote: “Marine oxygen isotope data indicate that the Earth has been in a ‘greenhouse’ mode for approx. 80 % of the past 500 million years (Spicer and Chapman, 1990; Frakes et al., 1992). Between the Mesozoic and early Tertiary [250 to 50 million years ago (Ma)], the plant fossil record shows the presence of tall, dense coniferous forests on the high latitude landmasses (Spicer and Chapman, 1990). Such forests extended to 65–85°N during the Jurassic and Cretaceous periods in Alaska and northern Russia (Spicer and Herman, 2001), and to the high latitudes (75 to 85°S) of the southern hemisphere, including Antarctica (Jefferson, 1982; Francis, 1986; Falcon‐Lang et al., 2001), South America (Archangelsky, 1963), New Zealand (Pole, 1999; Thorn, 2001) and Australia (Douglas and Williams, 1982).”
#Falcon-Lang, C.J. et al. (2004): Palaeoecology of Late Cretaceous polar vegetation preserved in
the Hansen Point Volcanics, NW Ellesmere Island, Canada. Palaeogeography, Palaeoclimatology, Palaeoecology, Vol. 212 (1-2)
Quote: “During the Cretaceous greenhouse climate phase, conifer/fern-dominated forests grew well inside the polar circle at latitudes as high as 82°N and 75°S (Francis and Frakes, 1993; Spicer et al., 1992, 2002; Falcon-Lang et al., 2001; Falcon-Lang and Cantrill, 2002; Spicer, 2003). These forests must have been adapted to an unusual combination of two environmental parameters not experienced by any extant vegetation: a polar light regime characterized by dark winters and light summers (Read and Francis, 1992) and elevated atmospheric CO2 levels (Berner, 1994; Nordt et al., 2002). As such Cretaceous polar forests
represent an entirely extinct vegetation biome (Spicer and Chapman, 1990).”
The Beast Slowly Awakens
- The ancient continents almost resembled the world of today but not quite. India was still a continent-sized tropical island full of lush rainforests and exotic life, on its way to smash into Asia.
Today's India was part of a gigantic continent more than 200 million years ago: Gondwana. This broke apart 200 million years ago and the Indian Plate became an island around 130-120 million years ago, drifted northwards to collide with the Eurasian Plate around 55 million years ago. This process is still ongoing and the Himalayas are the result of this collision. Here you can find an animation about the plate tectonic evolution of India:
#Scotese, C.R. & Scotese, J.D., (2006): Plate Tectonic and Paleogeographic Evolution of India. PALEOMAP Project, Evanston, IL
https://www.youtube.com/watch?v=cr-yjSwQ4E4 (uploaded 2017, retrieved 2023)
- But this paradise also hosted something else. The Deccan Traps – a volcanic region a thousand kilometers wide and about to come to life in a dramatic fashion.
The traps are so-called flood basalts. In places they have a thickness of 2000 m and in total they cover an area of 500,000 square kilometers, which is the size of the whole of Spain. The largest amount was deposited around 68-65 million years.
#Haldar, S.K. (2017): 6.4.4.3 Deccan Traps Basalt. Deposits in Asia. In: Platinum-Nickel-Chromium Deposits - Geology, Exploration and Reserve Base.
https://www.sciencedirect.com/book/9780128020418/platinum-nickel-chromium-deposits
Quote: “The Deccan Traps flow basalt (65 Ma) is one of the largest volcanic features on Earth, and crops out over 500,000 sq. km of the west-central Indian subcontinent. The trap complex is predominantly composed of multiple layers of tholeiitic flood basalt. The thickness varies from more than 2000 m in the Western Ghats to over 1000 m in eastern part of the province to less than 100 m in some southeastern regions. The basalts progressively overlap the basement from north to south. Most flows are 10–50 m thick, and dip at < 0.5°.”
Dasgupta, S. & Mukherjee, S. (2019): 4.3 Western Deccan Region of Maharashtra. Chapter 16 - Remote Sensing in Lineament Identification: Examples from Western India. In: Volume 5: Problems and Solutions in Structural Geology and Tectonics. Developments in Structural Geology and Tectonics
Quote: “It is widely agreed that, on the basis of outcrop studies and geochronology data from dykes and other alkaline felsic rocks, that most the flood basalts emplaced (~ 65–68 Ma) prior to India-Seychelles break-up during ~ 63–64 Ma, the rifting of which initiated much earlier ~ 80 Ma (Collier et al., 2008; Ganerød et al., 2011; Misra et al., 2014).”
#Renne, P. (retrieved 2023): Map of Deccan Traps in India (IMAGE). Berkeley Geochronology Center & UC Berkeley
Quote: “This is a map showing the extent of the Deccan Traps volcanic region in India, which dates from 64-67 million years ago. The rectangle shows the region near Mumbai from which the Berkeley team obtained lava samples used in the new precision dating of the eruptions around the time of the asteroid or comet impact 66 million years ago.”
There are various hypotheses as to the cause. One is the “active rifting model”, a so-called mantle plume, i.e. mushroom-like magma that actively rose from the interior of the earth's mantle. The other main hypothesis is the “passive rifting model”, which is basically a thinning of the mantle or crust due to tectonic, opposing movements (rifting), causing mantle material to rise and to melt due to decompression.
#Das, A. & Paul, J. (2021): The Deccan Chronicle: Plume or no-Plume? Perspective from a Deccan dyke swarm.
Quote: “There exists an intense debate regarding Deccan’s emplacement invoking different hypotheses since decades. The most widely discussed ‘active rifting’ or ‘mantle plume’ model (Campbell, 2005; Duncan and Richards, 1991; Ernst and Buchan, 2003) suggests that the Deccan Volcanic Province (DVP) originated from the “head” of the Réunion plume in late Cretaceous (Fig. 1b). In this model, India-Seychelles separation and the Deccan eruption were both intrigued by the impingement of the Réunion plume at the base of the Indian lithosphere. Alternately ‘passive rifting model’ suggests an interplay of continental rifting and decompression melting due to small-scale mantle convection (Fig. 1b; King and Anderson, 1995; Hawkesworth et al., 2000; Sheth, 1999a, b; 2005).“
- About 800,000 years before the impact, the Deccan Traps began to exhale about 10 million tonnes of CO2 and sulfur dioxide each year. Which in the grand scheme of things was not that much, so for a long time no one noticed. The problem was, these emissions wouldn’t stop. For half a million years, they started to dangerously pile up in the atmosphere.
The outgassing of CO2 and sulfur (red and blue lines, “Gt” = “gigatonnes” = 1.000.000.000 tonnes) can be recalculated using drill cores that record calcareous sediments from fossil marine microorganisms (we explain more about this below).
#Cox, A.A & Brenhin, C.K. (2023): A Bayesian inversion for emissions and export productivity across the end-Cretaceous boundary. Science, Vol. 381
https://www.science.org/doi/10.1126/science.adh3875
Quote: “Approximately 32,000 and 15,000 Gt of carbon and sulfur emissions, respectively, are required by the model to reproduce K/Pg conditions with a CO2 doubling rate of 2.9° ± 0.3° (Fig. 3A). One-third of this volume is before the boundary, with similar amounts of carbon and sulfur emitted from 66.8 to 66.3 Ma, reflecting potential passive degassing because these signals pre-date all but perhaps the very first known Deccan Traps eruptions (42, 43) (Fig. 4A). At 66.3 Ma, a noticeable increase in carbon output and decrease in sulfur output occurs, coincident with the oldest Deccan flows dated by Eddy et al. (42) and the initiation of the late-Maastrichtian warming event.”
For comparison: in 2023, global CO2 emissions were almost 37 billion tons.
#Global Carbon Project (2023): Briefing on key messages Global Carbon Budget 2023
https://drive.google.com/file/d/1gDztPwVlt_pvrH6vffPWqoHhqhM_mAJI/view?usp=sharing
Quote: “Global emissions from fossil use are projected to rise 1.1% in 2023 (range 0.0% to 2.1%),
reaching 36.8 billion tonnes of carbon dioxide (GtCO2), with rises expected in all fuel types (coal, oil, natural gas).”
- About 300,000 years before the asteroid, the Deccan Traps started to vomit lava. This was nothing like a normal eruption – it was a lava flood. Imagine a landscape with volcanos stretching beyond the horizon. They were constantly active, releasing a steady flow of massive amounts of poison and lava, interrupted by much more violent and deadly eruptions.
A study has taken sediment and rock samples from the 9 main layers of the flood basalts. They analyzed small crystals (zircons) and determined their age using uranium-lead dating. This method analyzes the decay rate of uranium to lead, which can be used to determine how old the rock is.
This method led to four large magmatic pulses (the red-brown curve), while the first began about 66.3 million years ago and the fourth ended about 65.5 million years ago. The strongest eruptions occurred directly before or after the impact of the meteorite.
The most massive pulse was before the impact and was characterized by eruption rates of up to 11 cubic kilometers per year. For comparison: current global volcanic production is 3 to 4 cubic kilometers (red line).
#Schoene, B. et al. (2019): U-Pb constraints on pulsed eruption of the Deccan Traps across the end-Cretaceous mass extinction. Science, Vol. 363 (6429)
https://www.science.org/doi/10.1126/science.aau2422
Quote: “Our results showed that the Deccan Traps erupted in four high-volume events, each lasting ≤100 ka, separated by periods of relative volcanic quiescence. The first event corresponded to the eruption of the lowermost seven formations from ~66.3 to 66.15 Ma ago; the second to the Poladpur Formation from ~66.1 to 66.0 Ma ago; the third to the Ambenali Formation from ~65.9 to 65.8 Ma ago; and the fourth and final to the uppermost Mahabaleshwar Formation, from ~65.6 to 65.5 Ma ago.”
The Beast Turns Furious
- First the planet experienced a wave of heating, with oceans getting at least 2ºC hotter in just 100,000 years.
Figure 1A shows a reconstruction of the temperatures based on analysis of marine sediments. Some microorganisms (e.g. foraminifera) build shells from calcium carbonate. When they die, they are deposited on the sea floor and can form massive sediments over millions of years (sediments or rocks that we call "limestone", for example).
Depending on the ocean temperature, these microorganisms build different ratios of different oxygen isotopes into their shells. If this ratio is measured, conclusions can be drawn about the ocean temperature at which these organisms lived.
The red graph shows the temperature difference over time (ΔT). It can be seen that from around 66.3 million years ago, temperatures rose rapidly and then fell again after a few hundred thousand years to 66 million years ago. They also rose again afterwards, even if more slowly than before.
#Cox, A.A & Brenhin, C.K. (2023): A Bayesian inversion for emissions and export productivity across the end-Cretaceous boundary. Science, Vol. 381
Figure 2B shows a similar temperature curve. The colored dots represent different locations where drill cores were taken ("ODP" = Ocean Drilling Program). Here too, ΔT rises from around 66.3 and falls again until 66 million years before today.
#Schoene, B. et al. (2019): U-Pb constraints on pulsed eruption of the Deccan Traps across the end-Cretaceous mass extinction. Science, Vol. 363 (6429)
https://www.science.org/doi/10.1126/science.aau2422
Quote: “As an initial attempt to correlate our eruptive history with paleoenvironmental data, we used two proxy records across the K-Pg transition (Fig. 2B). Benthic foraminifera δ18O compositions indicate ~2° to 4°C of deep ocean warming over ~150 ka, beginning at the C30n-C29r magnetic reversal (~66.3 Ma ago), followed by cooling over ~150 ka prior to the KPB (35–37). It has also been argued on the basis of δ18O data from Elles, Tunisia, that renewed warming began tens of thousands of years before the KPB (38) (fig. S11).”
- Some of the gasses of the Deccan Traps heated the planet up, while others would cooled it down. But the mix was uneven, so after the initial warming, a period of cooling followed, massively stressing the ecosystems that barely managed to adapt to the hotter temperatures.
Bond, D.P.G. & Wignall, P.B. (2014): Large igneous provinces and mass extinctions: An update. In: Volcanism, Impacts, and Mass Extinctions: Causes and Effects (pp.29-55)
Quote: “Apart from water vapor (H2O), carbon dioxide (CO2) and sulfur dioxide (SO2) are volumetrically the most important volcanic gases. Both are greenhouse gases, but their warming effects operate over very different time scales: Only CO2 causes significant warming over geological time. While SO2 causes localized short-term warming over periods of days to weeks, its major effect is that of cooling because it forms sunlightblocking aerosols. Chlorine and fluorine are other important products of volcanism, contributing to ozone depletion and acid rain (e.g., Sigurdsson, 1990; Thordarson and Self, 1993, 2003).”
In the following diagram we would like to give an overview of the possible causes and effects of large igneous provinces (LIPs) using the example of the Siberian Traps, which caused the largest known extinction event at the Permian-Triassic boundary around 250 million years ago.
Bond, D.P.G. & Wignall, P.B. (2014): Large igneous provinces and mass extinctions: An update. In: Volcanism, Impacts, and Mass Extinctions: Causes and Effects (pp.29-55)
The following diagram is similar, this time with the terrestrial or marine ecosystem embedded.
#Clapham, M.E. & Renne, P.R. (2018): Flood Basalts and Mass Extinctions. Annual Review of Earth and Planetary Sciences, Vol. 47
https://www.annualreviews.org/doi/abs/10.1146/annurev-earth-053018-060136
- At the same time, the sulfur in the atmosphere came back down as acid rain, while the CO2 was acidifying the ocean and killing the plankton – which was, and still is today, the basis of the food web in the oceans.
#Schoene, B. et al. (2019): U-Pb constraints on pulsed eruption of the Deccan Traps across the end-Cretaceous mass extinction. Science, Vol. 363 (6429)
https://www.science.org/doi/10.1126/science.aau2422
Quote: “Two models of environmental change from volcanic activity relate to eruptive volatile emissions (1, 4). The first is volcanogenic CO2 release, with associated global warming, ocean acidification, and carbon cycle disruption. The second is SO2 injection into the stratosphere and its conversion to sulfate aerosols, causing global cooling, acid rain, and ecosystem poisoning (5).”
Bond, D.P.G. & Wignall, P.B. (2014): Large igneous provinces and mass extinctions: An update. In: Volcanism, Impacts, and Mass Extinctions: Causes and Effects (pp.29-55)
Quote: “Another potentially important effect of CO2 release is increased acidity of the oceans. Huybers and Langmuir (2009) modeled the effect of increased atmospheric CO2 on carbonate saturation and showed that a rapid injection of ~3000 Gt of CO2 into the ocean, accompanied by a 4 °C ocean warming and 100 ppm increase in atmospheric CO2 concentration, would cause the carbonate saturation horizon to shoal by ~1 km (Fig. 4). If correct, Huybers and Langmuir’s (2009) modeling implies that the largest subaerial large igneous province eruptions were able to generate signifi cant ocean acidifi cation, as has been proposed for the end-Permian mass extinction (Payne et al., 2007). However, these effects would only be severe in cooler, higher-latitude oceans and in deeper waters.”
#Schmidt, A. et al. (2016): Selective environmental stress from sulphur emitted by continental flood basalt eruptions. Nature Geoscience, Vol. 9
https://www.nature.com/articles/ngeo2588
Quote: “It is well known from observations of historic eruptions that emissions of magmatic sulphur dioxide (SO2) and its oxidation products, such as sulphuric acid aerosol, are the main agents able to induce profound climatic and environmental change11,12. Consequently, climatic cooling and environmental acidification due to the emission and deposition of large quantities of magmatic sulphur (‘acid rain’) are two widely proposed causal agents for global biotic crises coinciding with periods of CFB volcanism9,13–15.”
- About 50,000 years before impact, the true apocalypse came. Like a cosmic horror breaking out of its prison, the Deccan Traps roared and screamed and began to spew out tens of trillions of tons of magma and even more deadly gasses in an onslaught that lasted for several thousand years.
As previously mentioned, the pulse with the highest eruption rates took place before the impact: About 50,000 years ago, the peak eruption rate was around 11 cubic kilometers per year. If we assume, for simplification, that basalt has a density of 3 tons per cubic meter, then this results in the following calculation for the weight:
11 km3 x 1000 = 1.1x1010 m3
1.1x1010 m3 x 3 (density of basalt in to/m3) = 33.000.000.000 = 33 billion tons of basalt per year.
If we simply assume that this period with this high rate lasted 1.000 years, we end up with 33 trillion tons. If we now consider that the pulse was still active for several tens of thousands of years until the impact ( even if at decreasing rates), we are faced with orders of magnitude that simply cannot be grasped.
#Schoene, B. et al. (2019): U-Pb constraints on pulsed eruption of the Deccan Traps across the end-Cretaceous mass extinction. Science, Vol. 363 (6429)
- So much heat was released from the roaring hot interior of our planet that it might have created hypercanes – cyclones tens of kilometers wide, with winds reaching almost 1000 km/h – 3 times more than the deadliest hurricane ever recorded by humanity. These storms were so massive and intense that they could reach tens of kilometers into the stratosphere and rip holes into the ozone layer, with devastating consequences for all life, now without protection from the sun’s radiation.
Hypercanes are theoretical models. Abnormally high water temperatures of at least 50°C are assumed to be the basis for their formation.
Among other things, large quantities of water vapor are brought to high altitudes, which have an impact on the ozone layer. The ozone layer protects the earth from the sun's radiation. Ozone (O3), a gas, absorbs harmful UV-B radiation and is thus split into an oxygen molecule and an oxygen atom, which can react again to form ozone. However, the additional water means that there are more reactants to split the ozone. It breaks down more and more.
#Emanuel, K. A. et al (1995): Hypercanes: A possible link in global extinction scenarios. Journal of Geophysical Research, Vol. 100, (D7)
https://archimer.ifremer.fr/doc/00258/36966/35611.pdf
Quote: “Our present purpose is to suggest hat in at least some cases of oceanic massive volcanism or bolide impact, hypothetical atmospheric storms known as hypercanes may have played an essential role in injecting material into the stratosphere. Hypercanes are extraordinarily intense hurricanes whose energy production is so large that it cannot be balanced by surface dissipation, resulting in storms that are so intense that internal dissipation becomes important. These storms are hypothesized to occur when the degree of air-sea thermodynamic equilibrium exceeds a theoretically defined threshold value. Their circulations would penetrate to high altitudes in the stratosphere, where they could deposit large quantities of mass, including water vapor, condensed water, and volcanic ash.
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This is enough to replace the entire mass of the atmosphere between the 100- and 50-mbar pressure surfaces in about 6 months. Two aspects of this mass transport are of particular interest: (1) the flux of water substance, which has the potential of radically altering radiative transfer through the stratosphere and of affecting atmospheric chemistry and (2) the flux of aerosols, which also may alter radiative transfer.
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The injection of large amounts of water into the stratosphere may have significant consequences for the chemistry of that region. Water vapor is the source of the free radicals OH and HO2, which contribute to stratospheric ozone depletion through the following catalytic cycle:
OH + O3 > HO2 + O2
HO2 + O3 > OH + 2 O2
Net: 2 O3 > 3 O2
This is the reaction couplet that contributes most to ozone destruction in the lower stratosphere; it is followed in importance by catalytic cycles involving nitrogen oxides and halogen free radicals.
- Giant clouds loaded with mercury and hydrochloric acid rolled over the planet, delivering the final blow to the remnants of a once magnificent and fertile world.
Even if it is not yet entirely certain what role mercury, one of the most toxic elements in the world really played in the extinction of the dinosaurs (or in extinction events in general: It has been shown that Deccan volcanism and other (LIP events) led to increased levels of mercury in sediments. The mercury released by the volcanoes ended up in the oceans and was incorporated into the shells of microorganisms in the sea.
#Keller, G. et al. (2020): Mercury linked to Deccan Traps volcanism, climate change and the end-Cretaceous mass extinction. Global and Planetary Change, Vol. 194
https://www.sciencedirect.com/science/article/abs/pii/S0921818120302034
Quote: “Linking Deccan Traps LIP volcanism to climate warming and the end-Cretaceous mass extinction requires a reliable proxy for volcanic emissions, as well as sedimentary sequences with complete bio- and chemo-stratigraphic records across the KPB. One such potential proxy is stratigraphic mercury (Hg). Volcanic eruptions are the main source of natural Hg to the atmosphere (Pyle and Mather, 2003; Pirrone et al., 2010). Following eruptions, Hg is distributed globally during its atmospheric residence time of six months to one year prior to precipitation and deposition in terrestrial and marine environments (Pyle and Mather, 2003; Fitzgerald et al., 2007; Percival et al., 2015; review in Grasby et al., 2019). Mercury anomalies in sediments of the Late Permian mass extinction yielded a promising LIP volcanism proxy (Sanei et al., 2012; Grasby et al., 2013), which marked a major turning point in mass extinction studies. Since then, all five major mass extinctions have yielded Hg anomalies in marine and terrestrial sediments, hypothesized to derive from LIPs, thus potentially providing a direct link between LIP volcanism, climate change and biotic crises (e.g., Grasby et al., 2016; Font et al., 2016; Thibodeau et al., 2016; Sial et al., 2016, 2020; Gong et al., 2017; Jones et al., 2017; Percival et al., 2017; Thibodeau and Bergquist, 2017; Shen et al., 2019; review in Grasby et al., 2019).
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Volcanism is the most important natural source of Hg to the atmosphere, with a residence time of six months to a year during which Hg is globally distributed prior to precipitation and deposition in terrestrial and marine environments (review in Grasby et al., 2019). In marine environments, direct atmospheric fallout of Hg accounts for about 70% while the other 30% is bound to organic matter (OM) and transported by rivers into ocean margins, of which only 28% reaches the open ocean (Amos et al., 2014; Holmes et al., 2010). In marginal marine sediments, Hg is primarily adsorbed onto OM yielding Hg spikes during pulsed LIP eruptions (Amos et al., 2014; Fitzgerald and Lamborg, 2014; review in Grasby et al., 2019). Model results for LIP eruptions during the endPermian mass extinction predict that Hg emissions orders of magnitudes greater than normal background conditions could have generated a series of toxic shocks, each lasting > 1000 years (Grasby et al., 2020). Similar conditions likely prevailed during the maximum Deccan eruption pulse and hyperthermal warming near the end-Cretaceous mass extinction.
(...)
Results demonstrate Deccan volcanism's long-term detrimental effects on marine life and reveal paroxysmal eruptions, toxicity and ocean acidification as a critical driver of the rapid mass extinctions.”
Mercury concentrations were highest in the last tens of thousands of years in particular, although very high levels were also found in isolated cases in the 500,000 years before that.
#Keller, G. et al. (2020): Mercury linked to Deccan Traps volcanism, climate change and the end-Cretaceous mass extinction. Global and Planetary Change, Vol. 194
https://www.sciencedirect.com/science/article/abs/pii/S0921818120302034
For other mass extinction events, such as the Siberian Traps, there are signs of mercury concentrations that could have led to toxic shocks for marine animals, land animals and plants.
#Grasby, E. S. et al. (2020): Toxic mercury pulses into late Permian terrestrial and marine
environments. Geology, Vol. 48(8)
Quote: “Model results for a LIP eruption predict that pulses of Hg emissions to the atmosphere would have been orders of magnitude greater than normal background conditions. When deposited into world environments, this would have generated a series of toxic shocks, each lasting >1000 yr. Such repeated Hg loading events would have had severe impact across marine trophic levels, as well as been toxic to terrestrial plant and animal life. Such high Hg loading rates may help explain the co-occurrence of marine and terrestrial extinctions.
Even if the specific effects of hydrogen chloride and hydrogen acid are unclear, there are also recent examples of how these substances have damaged the environment after volcanic eruptions.
#Bond, D.P.G. & Wignall, P.B. (2014): Large igneous provinces and mass extinctions: An update. In: Volcanism, Impacts, and Mass Extinctions: Causes and Effects (pp.29-55)
Quote: “Hydrogen chloride and hydrogen fluoride (HCl and HF), volcanic ash in the form of silicate particulate matter, and methane (CH4 ) are other important products of volcanism. Some of these have been documented as causing environmental harm during recent eruptions, leading to their effects being invoked in mass extinction scenarios (without much acclaim). In particular, HCl causes damage downwind from volcanoes because HCl and H2O condense readily on ash particles and fall as acidic rain. This mechanism affected crops and livestock in Iceland and mainland Europe during the 1783–1784 Laki eruptions, which released 7 Mt of HCl (Thordarson and Self, 1993, 2003). However, this rainfall also ensures the swift removal of volcanic HCl from the atmosphere, and it is unlikely that HCl could cause long-term damage on a global scale. HCl also destroys ozone as reactive chlorine atoms are released through interaction with sulfate aerosols, but due to the rapid scrubbing of HCl from the troposphere by rain, there is limited opportunity for stratospheric ozone destruction.”
- Like a cosmic joke, on the other side of the world, a bright dot of light appeared in the sky. And an instant later, an asteroid 10 km across smashed into earth with the power of 4 billion atomic bombs. If you want to see what this was like, we made a whole video about it. If life on earth was like a murder victim barely holding on this was the final blow. Just too much.
In the video mentioned below, we take a different theory as a basis: we discuss that the asteroid could have been mainly responsible for the extinction of the dinosaurs and that it could even have triggered the Deccan volcanism.
As we explain further below, there are a number of different theories about the Cretaceous mass extinction and scientists are actively debating the various possibilities. We at kurzgesagt also want to present different points of view and therefore the theories in this video differ from those in the earlier video mentioned below.
#Kurzgesagt (2001): The Day the Dinosaurs Died – Minute by Minute
https://www.youtube.com/watch?v=dFCbJmgeHmA
- When they eventually finished and truly went back to sleep, 75% of all species on Earth had perished.
For a good overview and summary of the Cretaceous mass extinction event and all so-called 'Big Five' mass extinction events, including timescales, environmental impacts, possible causes and further information, see Anthony, D. B. et al.
#Anthony, D. B. et al. (2011): Has the Earth’s sixth mass extinction already arrived? Nature, Vol. 471
- There are other ones that paint a different picture but right now scientists are still fiercely arguing over this, check our sources to learn more.
Although in the last years the evidence for the Deccan Traps has been rising considerably, there a numerous other explanations. t's impossible to make a fair and representative review of the literature, but here are some examples.
This paper provides a link between the impact and increased volcanic activity.
#Renne, P. R. et al. (2015): State shift in Deccan volcanism at the Cretaceous-Paleogene boundary, possibly induced by impact. Science, Vol. 350 (6256)
https://www.science.org/doi/10.1126/science.aac7549
Quote: “The existing Deccan Traps magmatic system underwent a state shift approximately coincident with the Chicxulub impact and the terminal-Cretaceous mass extinctions, after which ~70% of the Traps' total volume was extruded in more massive and more episodic eruptions. Initiation of this new regime occurred within ~50,000 years of the impact, which is consistent with transient effects of impact-induced seismic energy.”
Other sources investigate the climatic effect of outgassing from volcanic activity and climate changes due to the asteroid impact and come to the result that volcanic activity had no influence on the mass extinction event
#Hull, P. M. (2020): On impact and volcanism across the Cretaceous-Paleogene boundary. Science, Vol. 367 (6475)
https://www.science.org/doi/10.1126/science.aay5055#sec-2
Quote: “The cause of the end-Cretaceous mass extinction is vigorously debated, owing to the occurrence of a very large bolide impact and flood basalt volcanism near the boundary. Disentangling their relative importance is complicated by uncertainty regarding kill mechanisms and the relative timing of volcanogenic outgassing, impact, and extinction. We used carbon cycle modeling and paleotemperature records to constrain the timing of volcanogenic outgassing. We found support for major outgassing beginning and ending distinctly before the impact, with only the impact coinciding with mass extinction and biologically amplified carbon cycle change. Our models show that these extinction-related carbon cycle changes would have allowed the ocean to absorb massive amounts of carbon dioxide, thus limiting the global warming otherwise expected from postextinction volcanism.”
Other studies postulate that volcanic activity and impact events were practically hand in hand responsible for the mass extinction and that neither the Deccan Trapps nor the asteroid alone could be responsible for the extinction at the end of the Cretaceous.
#Arens, N. C. & West, I. D. (20089): Press-pulse: a general theory of mass extinction? Paleobiology, Vol. 34 (4)
Quote: “We found that the highest frequency of intervals with elevated extinction occurred when continental flood basalt volcanism and bolide impact co-occurred. In contrast, neither volcanism nor impact alone yielded statistically elevated extinction frequencies. Although the magnitude of extinction was uncorrelated with the size of the associated flood basalt or impact structure, crater diameter did correlate with extinction percentage when volcanism and impact coincided. Despite this result, case-by-case analysis showed that the volcanism-impact hypothesis alone cannot explain all intervals of elevated extinction. Continental flood volcanism and impact share important ecological features with other proposed extinction mechanisms. Impacts, like marine anoxic incursions, are pulse disturbances that are sudden and catastrophic, and cause extensive mortality. Volcanism, like climate and sea level change, is a press disturbance that alters community composition by placing multigenerational stress on ecosystems. We propose that the coincidence of press and pulse events, not merely volcanism and impact, is required to produce the greatest episodes of dying in Phanerozoic history.”
Sprain, C.J. et al. (2019): The eruptive tempo of Deccan volcanism in relation to the Cretaceous-Paleogene boundary. Science, Vol. 363 (6429)
https://www.science.org/doi/10.1126/science.aav1446
Quote: “Late Cretaceous records of environmental change suggest that Deccan Traps (DT) volcanism contributed to the Cretaceous-Paleogene boundary (KPB) ecosystem crisis. However, testing this hypothesis requires identification of the KPB in the DT. We constrain the location of the KPB with high-precision argon-40/argon-39 data to be coincident with changes in the magmatic plumbing system. We also found that the DT did not erupt in three discrete large pulses and that >90% of DT volume erupted in <1 million years, with ~75% emplaced post-KPB. Late Cretaceous records of climate change coincide temporally with the eruption of the smallest DT phases, suggesting that either the release of climate-modifying gases is not directly related to eruptive volume or DT volcanism was not the source of Late Cretaceous climate change.”
- As we learn more and more about the past, we found that at least 4 of the 5 big mass extinctions happened at the same time as the Earth was furiously spewing gargantuan amounts of magma.
The following paper provides a good introduction to the topic of flood basalts (so-called “large igneous provinces” or “LIPs”) and their effects and also shows that there is a connection between flood basalts and mass extinction events that is not coincidental. However, it should be noted that the trigger for such mass extinctions isn't a certainty.
#Green, T. et al. (2022): Continental flood basalts drive Phanerozoic extinctions. PNAS, Vol. 119 (38)
https://www.pnas.org/doi/full/10.1073/pnas.2120441119#sec-4
Quote: “Fed by extensive dike systems and composed of volatile-bearing volcanics brought up from the deep mantle in plumes, LIPs—especially in their mafic guise as flood basalt provinces—have had pronounced effects on the climate history of Earth (5). Ocean anoxic events (OAEs), global warming (via CO2 and CH4), and short-term global cooling (via SO2) have all been attributed to flood basalt volcanism (3, 6, 7). Most remarkably, at least four of the five mass extinctions of the Phanerozoic coincide with flood basalt eruptions: the Deccan Traps at the Cretaceous–Paleogene (K-Pg) boundary, the Central Atlantic Magmatic Province (CAMP) at the Triassic–Jurassic boundary, the Siberian Traps at the Permo–Triassic boundary, and, more tentatively, the Viluy or Kola-Dnieper Provinces at the Frasnian–Famennian boundary (3, 5, 6); mafic magmatism is speculated at the Late Ordovician mass extinction as well, but has not been correlated with a specific known LIP (3, 8).”
(...)
“However, the extent to which such correlations are likely to occur by chance has yet to be quantitatively tested, and other kill mechanisms have been suggested for many mass extinctions. Here, we show that the degree of temporal correlation between continental LIPs and faunal turnover in the Phanerozoic is unlikely to occur by chance, suggesting a causal relationship linking extinctions and continental flood basalts. The relationship is stronger for LIPs with higher estimated eruptive rates and for stage boundaries with higher extinction magnitudes. This suggests LIP magma degassing as a primary kill mechanism for mass extinctions and other intervals of faunal turnover, which may be related to CO2, SO2, Cl, and F release. Our results suggest continental LIPs as a major, direct driver of extinctions throughout the Phanerozoic.
(...)
Our results suggest that CFB eruptions are a primary known driver of mass extinction throughout the Phanerozoic. While it is difficult to assign the causal mechanism for any single given extinction on the basis of temporal correlation alone, the broader correlation across the Phanerozoic between faunal turnover and LIP eruptions (Fig. 1) is extraordinarily unlikely to have arisen by chance. In the absence of an external mechanism producing the mantle plumes that drive LIP eruptions and the environmental perturbations that lead to extinctions, this degree of correlation suggests a causal relationship. This observed correlation between extinction and LIP eruption pertains both for mass extinctions and lesser faunal turnovers, but is strongest for boundaries with higher rates of extinction and flood basalts with higher bulk eruptive rates (Fig. 2).”
Without going into detail here, the individual diagrams show the extent to which the observed coincidences between flood basalts (and impacts) and various mass extinction events deviate in comparison to the random probability (referred to here as the "stochastic distribution") of the two events coinciding. In short, the smaller p is, the less likely it is that both events are a coincidence.
Diagram E to H also shows the effect that asteroid impacts can have had. Since p (compared to the flood basalt calculations A to D) is considerably higher in some cases, they seem to coincide with mass extinction events.
It is also interesting to note that if the asteroid impact that is suspected of having wiped out the dinosaurs (referred to here as "Chicxulub") is removed from the calculation (F and H), the probability of a coincidence is even higher
A small indication that the asteroid could have had at least some influence on the mass extinction at the end of the Cretaceous.
Quote (caption): “Relationship between observed and expected coincidence products. The observed coincidence products between all Phanerozoic stage boundaries and all LIPs (A), along with the corresponding stochastic distribution (which would result if timescale boundaries were spread randomly throughout the Phanerozoic following a uniform distribution), on a logarithmic y scale. The probability that a uniform distribution has a higher coincidence product (
) than observed is given by P. Note that the vertical log scale visually distorts the shaded regions compared to the reported P values. B shows the results for LIPs and stage boundaries when the Siberian Traps, the largest LIP correlated with a severe extinction, is excluded. C shows the coincidence products for all LIPs and the five Phanerozoic mass-extinction boundaries. D shows the results for LIPs and stage boundaries when all of the LIPs temporally correlated with mass extinctions (the Deccan Traps, CAMP, Siberian Traps, Viluy Province, and Kola-Dnieper Province) are not considered. Even without these large, well-correlated events in B and D, there is still a statistically significant relationship between LIPs and Phanerozoic extinctions. Below are the observed coincidence products and stochastic distributions of coincidence products for impact events. E shows the results for all impacts with diameters ≥20 km and all stage boundaries, while F excludes the Chicxulub impactor from consideration. Likewise, G shows the results for all impacts with diameters
≥40 km and all stage boundaries, while H excludes the Chicxulub. The coincidences between impact events and Phanerozoic extinction are statistically significant only when the Chicxulub impactor is included, indicating that its precise coincidence with the K-Pg mass extinction is primarily responsible for the observed relationship between impacts and extinctions. Since the LIP-extinction coincidence is robust to similar exclusions, this supports a significant temporal relationship between LIPs and faunal turnover over the Phanerozoic.”
- The worst massacre ever, the Permian mass extinction 250 million years ago, was caused by the Siberian Traps – a hellish flood of lava that killed 95% of all the species on earth, almost bringing life to its knees.
#Ivanov, A. V. et al. (2013): Siberian Traps large igneous province: Evidence for two flood basalt pulses around the Permo-Triassic boundary and in the Middle Triassic, and contemporaneous granitic magmatism. Earth-Science Reviews, Vol. 122
https://www.sciencedirect.com/science/article/abs/pii/S0012825213000652
Quote: “The Siberian Traps large igneous province is of enormous size (~ 7 × 106 km2) and volume (~ 4 × 106 km3).”
Analysis of geological records puts these eruptions as directly coinciding with the worst extinction in the planet’s history, and very likely having caused massive climate change due to the addition of enormous amounts of greenhouse gases into the atmosphere.
#Burgess, S. D. & Bowring, S. A. (2015): High-precision geochronology confirms voluminous magmatism before, during, and after Earth’s most severe extinction. Science Advances, Vol. 1 (7)
https://www.science.org/doi/10.1126/sciadv.1500470
Quote: “The end-Permian mass extinction was the most severe in the Phanerozoic, extinguishing more than 90% of marine and 75% of terrestrial species in a maximum of 61 ± 48 ky. Because of broad temporal coincidence between the biotic crisis and one of the most voluminous continental volcanic eruptions since the origin of animals, the Siberian Traps large igneous province (LIP), a causal connection has long been suggested. Magmatism is hypothesized to have caused rapid injection of massive amounts of greenhouse gases into the atmosphere, driving climate change and subsequent destabilization of the biosphere.”
It has been argued that the temperatures reached lethal levels:
#Sun, Y. et al. (2012): Lethally Hot Temperatures During the Early Triassic Greenhouse. Science, Vol. 338
Quote: “The late Smithian Thermal Maximum (LSTM) marks the hottest interval of entire Early Triassic, when upper water column temperatures approached 38°C with SSTs possibly exceeding 40°C”
And that the global effects might have lasted for millions of years:
#Chen, Z. Q. & Benton, M. J. (2012): The timing and pattern of biotic recovery following the end-Permian mass extinction. Nature Geoscience, Vol. 5
Quote: “The aftermath of the great end-Permian period mass extinction 252 Myr ago shows how life can recover from the loss of >90% species globally. The crisis was triggered by a number of physical environmental shocks (global warming, acid rain, ocean acidification and ocean anoxia), and some of these were repeated over the next 5–6 Myr. [...] a stable, complex ecosystem did not re-emerge until the beginning of the Middle Triassic, 8–9 Myr after the crisis.”
- Until recently, many scientists thought that this was an outlier, but new evidence suggests it may have been the rule. Other big mass extinctions happened when the monster awoke from its sleep and the longer and more violently it rampaged, the more slaughter we can see in the fossil record.
#Green, T. et al. (2022): Continental flood basalts drive Phanerozoic extinctions. PNAS, Vol. 119 (38)
https://www.pnas.org/doi/full/10.1073/pnas.2120441119#sec-4
Quote: “If the observed degree of temporal coincidence between LIPs and faunal turnover is the result of a causal relationship, we might further expect larger LIPs to be associated with more severe extinctions. However, such a correlation, at least with absolute LIP magnitude, has not been previously observed (3, 32–34). Rather than absolute magnitude, we consider, instead, “bulk eruption rate”—that is, the total volume of the LIP divided by the best estimate of the total duration over which that bulk was erupted—as a critical parameter. While more difficult to quantify than magnitudes alone (requiring accurate geochronology), rates are highly relevant in the context of critical thresholds in climatic and ecological stability (35–37).
(...)
The additional correlation we observe between bulk eruption rate and extinction magnitude (Fig. 4) allows a direct estimation of the degree to which the severity of a given mass extinction corresponds with the expected severity if the extinction were caused by a coincident CFB eruption alone. The linearity of this correlation indicates that the deadly consequences of CFBs are, in general, directly proportional to their total volumetric eruption rate, though intrusive and passive degassing may well play a critical role in the timing of volatile release.”
- Definitely not. While the monster is real, it is amazingly slow and currently very sleepy. If it were about to awake again, scientists monitoring the Earth’s interior would get a warning really early – maybe even millions of years in advance. Time enough to prepare and move out of the way.
The idea behind it is very complex and abstract. However, the following article summarizes it well and is based, among other things, on the following source.
#Howard, L. (2017): When will the Earth try to kill us again? Arstechnica
https://arstechnica.com/science/2017/11/when-will-the-earth-try-to-kill-us-again/
Quote: “LIPs may be on a cycle. On average, there’s one every 15 million years, with the last occurring 16 million years ago (the Columbia River LIP in northwestern USA). By that rough reckoning, we are overdue for another. But Olson and others link LIPs to longer cycles in Earth’s magnetic field, which switch between eras of rapid magnetic field reversals (roughly every 200,000 years) to periods of no reversals (lasting 25 to 40 million years).
Since the churning of liquid metal that generates our magnetic field is driven by the flow of heat from the core, changes in how well the mantle insulates the core should, Olson argues, affect the magnetic field. Seismologists have mapped out two continent-sized hot regions in the lower mantle called “Large Low Shear Velocity Provinces” or “LLSVPs,” that peak 1,800 kilometers above the core-mantle boundary. Olson thinks these may go through a long-term cycle of growth followed by slumping, which paces core heat loss and magnetic reversals. He proposes that slumping LLSVPs also kick-start hyperactive mantle plumes, which erupt as LIPs 30 to 60 million years later.
On that cycle, we are due a switch from our current rapid-reversal era to a quiescent period. And if Olson is right, the field reversal will give us more than 30 million years’ advance warning of the next LIP (for perspective, human ancestors separated from chimp ancestors about 7 million years ago).”
#Olson, P. & Amit, H. (2015): Mantle superplumes induce geomagnetic superchrons. Frontiers in Earth Science, Vol. 3
https://www.frontiersin.org/articles/10.3389/feart.2015.00038/full
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