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I am curious to know if it would be highly probable that if the Bennu asteroid were to hit the Earth in 2182, and the point of impact is within a 500 mile radius of Yellowstone National Park, will it most likely trigger a super volcano at Yellowstone?

If an impact were to occur, the expected kinetic energy associated with the collision would be 1,200 megatons in TNT equivalent (for comparison, TNT equivalent of Little Boy was approx 0.015 megaton)..."
Wikipedia

I am thinking that such an impact would send massive shockwaves through the ground in all directions and that these shockwaves could cause huge cracks in the rock dome that covers the giant magma chamber at Yellowstone.

So, if the Bennu asteroid were to hit within a 500 mile radius of Yellowstone National Park, will it trigger a super volcano at Yellowstone?

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There is actually an hypothesis that large asteroid impacts can trigger volcanism at the antipodal point, where the seismic energy of the impact focuses. On Earth, it has been suggested that the Chicxulub impact could have triggered the main phase of the antipodal (and synchronous) Deccan Traps eruption (Richards et al., 2015). On Mars, the same process has been suggested (Williams & Greeley, 1994): Alba Mons, the largest volcano of the planet, is antipodal to Hellas Planitia, the largest impact structure. So, according to this hypothesis, for an impact to trigger an eruption at Yellowstone, it would have to occur at the antipodal point of the caldera, which is somewhere in the Indian Ocean, north from Kerguélen.

(Note: Part of this answer is copy/pasted from my answer to What if a global killer hit Mars? at Astronomy SE.)

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    $\begingroup$ The obvious problems with this is that Deccan was not on the opposite side of the Earth as Chixculub when the impact occurred, and volcanism was over an extended period - starting before the impact. $\endgroup$
    – winwaed
    Nov 1 '21 at 13:32
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    $\begingroup$ @winwaed The Deccan eruption had already begun, correct, but in their paper Richards et al. think that the impact triggered the later, most voluminous phase. I rephrased to make it clearer. Anyway it's just a theory, it's been quite debated but I thought it was worth mentioning! $\endgroup$ Nov 1 '21 at 14:30
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    $\begingroup$ @Jean-MariePrival If it's so hotly debated, wouldn't it be better described as a hypothesis than a theory? $\endgroup$
    – corsiKa
    Nov 2 '21 at 6:05
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    $\begingroup$ @corsiKa You're right, "hypothesis" is actually the term used by Richards et al. study. I've edited, thanks! $\endgroup$ Nov 2 '21 at 9:00
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    $\begingroup$ Thanks for the post. Has there been detailed modelling of how the shockwave(s) would be conducted and concentrated at various depths? $\endgroup$
    – Woody
    Nov 3 '21 at 3:09
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Maybe but it will depend on the state of the magma chamber under the caldera. If the magma chamber is already under enough pressure and has a super-eruptive quantity of liquid melt in it then the shock of a large bolide impact may act to "pop the cork" so to speak initiating a super eruption. I can also make an argument for shock nucleation of gas in the melt creating a pressure surge but that will depend on melt composition. So maybe BUT the right conditions are going to have to exist such that any similar shock, or none at all, would cause a super volcanic eruption anyway, the volcano will have to be close to eruption before the impact in other words.

Note that the Yellowstone caldera does go through cycles of seeming to be close to erupting and then backing off again so if the hit comes during a time of high pressure it could create an eruption that wouldn't have happened otherwise.

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  • $\begingroup$ Although I am not a scientist and I know very little about volcanology, your answer seems to me to be the most likely thing to occur if the Bennu asteroid were to hit near Yellowstone. $\endgroup$
    – user57467
    Nov 4 '21 at 22:01
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Bennu is about 470m diameter, and will impact at a "mere" 11.3km/s.

At the impact site it would blast a crater some 3 miles wide and 1500 ft deep, a very respectable impact indeed. The energy of impact is equivalent to a 6.6 moment magnitude earthquake at the surface at the impact location.

500 miles away, the impact will be neither felt not heard by human senses, but should be quite detectable by seismic instruments. This level of disturbance is unlikely to bother the magma under Yellowstone, it got shaken much harder during the 2011 Japanese earthquake.

Closer impact would be a different story, and an impact anywhere directly above the magma chamber will be a very bad thing. How close it would need to be is a difficult question though.

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  • $\begingroup$ "and will impact at a "mere" 11.3km/s" seems pessimistically certain.. According to the Wikipedia article referenced in the question, "It has a cumulative 1-in-1,800 chance of impacting Earth between 2178 and 2290 with the greatest risk being on 24 September 2182". $\endgroup$
    – TripeHound
    Nov 1 '21 at 21:40
  • $\begingroup$ @TripeHound How strange, i could have SWORN i did not include that bold on the "will". Thank you for misquoting me. As for the speed... The asteroid Bennu, if it does impact the Earth, will approach Earth at a trajectory that has virtually zero excess velocity. Thus Earth surface impact will be at Earth escape velocity plus about 80m/s $\endgroup$
    – PcMan
    Nov 1 '21 at 22:50
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    $\begingroup$ @TripeHound And yes, it is virtually certain that Bennu will eventually impact Earth. Its orbital shape and energy allow for only two possibilities: Either if gets 4+ consecutive gravity assists from Earth, allowing it to exit Earth's region around the sun, or it impacts Earth. The latter is enormously more likely, and soon too on astronomical timescales. Chance for impact withing 10 million years is better than 95% $\endgroup$
    – PcMan
    Nov 1 '21 at 22:54
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    $\begingroup$ (And all that, of course, ignores the possibility of human meddling. Redirecting asteroids has so far never been tried, and is not without some fairly serious risks and political complications, but if necessary, and given enough advance warning, we do already have various methods that should give us a fairly decent chance of turning a likely impact trajectory into an unlikely one.) $\endgroup$ Nov 1 '21 at 23:24
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    $\begingroup$ @IlmariKaronen yes, lunar impact is a possiblity. its subsumed by that 5% "other" category. The moon is such a tiny target, both physically and gravitationally. $\endgroup$
    – PcMan
    Nov 2 '21 at 6:07

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