# Tag Info

19

Mark's answer is correct, but in my opinion is not clear enough. Let's make it a bit simpler: Is it possible that the geomagnetic field reversal led to the extinction of Dinosaurs? NO, DEFINITELY NOT Here's why: The cause for the K-Pg extinction event (in which many living species, including dinosaurs, died) is well known: volcanic eruptions (the ...

15

The idea of mass extinction is not that recent actually: Cuvier (1798), Buckland (1823) and d'Orbigny (1851) for instance were already talking about global catastrophes in earth history, linked to extinctions. But during the same period, Brocchi (1814) and Lyell (1832) proposed that extinctions of species occurred individually and were a gradual process (...

13

It's a commonly-proposed theory that geomagnetic reversals cause extinction events, but there's no evidence for it. There aren't enough mass extinction events for any sort of statistical analysis, and there are a number of geologic processes that can give the illusion of simultaneous reversal and extinction. In particular, an erosion event can erase both ...

11

Some authors thinks that the extinction of the Pleistocene megafauna (large mammals such as mammoths, etc.) was contemporaneous with the Younger Dryas (Firestone et al. 2007; Faith & Surovell 2009), while some thinks that it predates it by a couple thousand years (Gill et al. 2009). Whether or not it was contemporaneous with the Younger Dryas, it ...

10

Though I agree with @kaberett that there is indeed more and more evidences that the Deccan volcanism was the main trigger of the K/Pg crisis, i wanted to add that there is a more nuanced hypothesis (that I heard about last week during a talk at EGU) according to which the Chicxulub impact resulting seismic response may be the trigger of one of the main stage ...

10

No, it did not definitively single-handedly cause the KT mass extinction event. Around the same time, the Deccan Traps Large Igneous Province (India) was being emplaced. Flood volcanism has been associated with other mass extinctions, due to the impact on climate, sunlight at the surface, etc, of the output of huge volumes of sulphur-based gases. The ...

9

Is there any consensus about the conjecture that gravitational force on Earth may have changed significantly over geological time; No, earth's gravity did not change significantly over time. Yes, earth's mass increases because of meteorites and decreases because of loss of some atmospheric gases to space, but it is extremely negligible. and in ...

8

I'll ignore the complete impossibility of getting the world's nuclear arsenal to the center of the Earth and the impossibility of exploding them all at once. The total number of nuclear weapons, including those held in reserve and those scheduled for dismantling, is about 15000, with an average explosive power of less than half a megaton of TNT. This is ...

8

As a preamble, let me say that I don't know remotely enough on galactic dynamic to know if a supernova could have possibly been close enough during the Ordovician for Earth to be affected by a gamma ray burst, nor do I know enough about geochemistry to know if there are ways to detect such an event in the fossil record. That being said, the questions that ...

8

You need to be very wary of anything written in the non-scientific media about science. The media loves woo and controversy because those are the things that garners readers, and that in turn garners advertising revenue. By way of analogy, suppose as near-adult in gym class someone said "My gym shoes smell bad. Bad! Awfully bad!" Someone else would ...

7

I can't be entirely sure but I'll make an informed guess: That value doesn't come for a single measurement. Therefore, if the error in the age of a single sample is $\pm125$ kyr, you just need to average 16 samples to get it down to $\pm31$ kyr. The uncertainty in the addition (or substraction) of two or more quantities is equal to the square root of the ...

6

Firstly, I'd like to state that so far there is no evidence that a civilization similar to ours has appeared on Earth before us. It might be apparent that we as a species have left quite a significant geological footprint, (if we didn't Archeologists would be out of a job!), and as of yet we've discovered no evidence to indicate a civilization that cannot ...

6

I'm not going to give an extensive account on "mass extinction" epistomology here but I think the first thing one has to consider is the difficulty of studying numerically paleobiodiversity (mostly because of a gappy fossil record but also an historically unbalanced sampling effort and the rock availability for some of the time periods); although, along the ...

5

The answer that you're asking is within the paper that you cited in the question: Did a gamma-ray burst initiate the late Ordovician mass extinction? (Melot et al). Specifically the section titled "ASPECTS OF THE LATE ORDOVICIAN MASS EXTINCTION POTENTIALLY COMPATIBLE WITH A GRB". But if you're looking for an article summary, here is the evidence they ...

5

There are several factors to consider. The main one is the atmosphere (especially if you want to compare Mars with the Earth's during magnetic reversals). Earth's atmosphere is a formidable shield against solar wind and cosmic radiation. Each type of radiation have a different penetration, but in general the radiation dose associated to each type of ...

5

Being in a submarine in the ocean is not a good idea because if a large asteroid hits the ocean the shock wave created, and its energy, would be very large. If the submarine survives intact its occupants may not. The occupants could be thrown about so much they liquidize & turn into people puree. Similarly being airborne in a blimp or airplane would be ...

3

There is one scenario in which climate change could render the Earth inhospitable to life in general, which would be a runaway greenhouse effect. In a runaway greenhouse effect, the Earth would get so hot that the oceans start to evaporate, adding more water vapour (powerful greenhouse gas) to the atmosphere, which will make it hotter yet, until Earth ends ...

3

As bon noted in the comments, that it the time it would take the gamma rays to reach Earth. Gamme rays travel at the same speed as all other forms of electromagnetic radiation, including visible light, so we will not have any warning. This kind of makes the "6000" number meaningless. We will know that the star exploded and the gamme rays will reach earth at ...

3

To add to David Hammen's answer. Earth is big. I hate to use the words "really really big" cause there are things much bigger, like the sun, but Earth is quite large. Imagine what would happen if all the Nukes went off 3000 miles from you. You're in LA, the bombs are all set off in NY. The curvature of the Earth would prevent you from seeing much, ...

3

Mass extinctions are selective: not all living organisms will be affected by it to the same extent. Meaning also that various groups will recover from it at various speed: a group from which half of the species were exterminated by the event will most probably take longer to recover (i. e. reach its pre-event diversity) than a group for which only 10% of the ...

3

A weed is just a plant where you do not want it. Totally a matter of context. Tumbleweeds are non-native, introduced centuries ago. I assume you mean the invasive species of plants that have been spread by humans and are disrupting ecologies throughout most of the world Until recently, these plants we consider weeds were limited in their range to home ...

2

Another good historical perspective from this blog: http://lablemminglounge.blogspot.com/2006/09/iridium-anomaly-as-historical-artifact.html Iridium anomaly as historical artifact Everybody knows that way back in 1980, Alvarez et al. showed that Italian sediments deposited on the Cretaceous / Tertiary boundary (and NOT the Cretaceous / Paleogene boundary, I ...

2

Almost nil on human time scales. The total estimated reserves (this number keeps changing over time) are of the order of 300E9 m^3. For convenience lets say all of this oil formed over the last 300 million years at a constant rate. Then the rate of formation is 1000 m^3 per year or ~6000 barrels of usable oil. This obviously is a simple back of the ...

2

Estimates of earth's total biomass vary widely, from 0.5 to 4 trillion tons C, so instead of citing a source, I'll just go with an assumption of $1\times10^{15} \text{kg C}$. Measuring biomass in carbon is a convenient segue to the next assumption: assume that all biomass burns only in $\text{CX + O}_2\,\rightarrow\,\text{CO}_2 + \text{X}$. Given these ...

2

National Geographic published an article about this in January 2018 - No, We're Not All Doomed by Earth's Magnetic Field Flip. Yes, the flipping of the magnetic poles does take a long time - thousands of years. But during the change, the Earth's magnetic field does not cease to exist & the magnetic poles do not disappear. They slowly migrate. For ...

2

Estimated sulfur release 325 gigatonnes = 325,000 teragrams. The numbers in this diagram are in teragrams Sulfur Cycle so the release is $\approx 1000\times$ today's annual sulfur cycle. I think most of the sulfur compounds would be washed into the ocean and then deposited into sediments. I can't find how much sulfur is currently in the oceans, this ...

1

100 years is not very long-term at all. The added CO2 will not miraculously disappear after a century, but will go on warming the planet. (And that's just assuming that humans stop burning fossil fuels now.) There are all sorts of feedback effects that will come into play at some point, if they haven't already. For one example, a lot of CO2 winds up ...

1

Depends on the further actions humanity takes. If we keep on pumping green house gases into the atmosphere, survival will become significantly harder. Sure, we most likely wont be able to create a Venus-like atmosphere, but as of today we simply do not know, what tipping points in the climate system we might go beyond. Actually I am more concerned by the ...

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