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> The phenomena and effects of airblast, ground shock, thermal radiation, cratering and ejecta, and debris cloud and deposition from the eruption of Mt St. Hele

> The phenomena and effects of airblast, ground shock, thermal radiation, cratering and ejecta, and debris cloud and deposition from the eruption of Mt St. Helens were compared to those that would result from a nuclear explosion to determine if phenomena or effects were analogous and thus might provide useful data for military nuclear weapon effects studies. It is concluded that the phenomena are not analogous. In particular, airblast destruction was caused by clouds of ash driven by subsonic winds, rather than by a supersonic shock wave that would be the-damage mechanism of a nuclear explosion. Because of the lack of analogy between the eruption and nuclear explosion phenomena, it appears questionable that any of the effects are analogous; therefore, it is unlikely that anything more of military interest can be gained from studying the effects of the eruption. However, key contacts for further information on the eruption and the associated research studies are given. The comparison of the eruption of Mt. St. Helens to the explosion of a 10- to 20-megaton nuclear weapon is misleading. Such comparisons serve no useful purpose and should be avoided. [1] https://apps.dtic.mil/sti/pdfs/ADA112420.pdf https://apps.dtic.mil/sti/pdfs/ADA112420.pdf

Taek 5y ago
Even though the damage types are not analogous people still want a crude metaphor for how "big" the blast was. Since people are going to compare it to a nuke regardless you might as well have some rough criteria for how a comparison could happen.
- kshacker 5y ago
  Why are people going to compare to a nuke? Because the media uses those terms. Maybe we need to suggest alternatives. Also since 1945, had there been just a single size of nukes? I may not have a sense of how big a Hiroshima nuke was as compared to a 1975 nuke vs a 2022 nuke. Just saying ... a better comparison (which I don't know as I am not a subject expert) could be developed. Maybe "enough energy to melt 1980 Antarctica" or some other similar scary comparison. Maybe "10 times the energy of hurricane Katrina" Edited the last 3 words
  - Jabbles 5y ago
    But those other examples suffer from the same flaw that no one has any intuitive understanding of how big those events are. - Tonga eruption was 1e7 tons - Hurricane Katrina was 1e10 tons - Melting Antarctica is 1e12 tons (afaict)
    - bryanrasmussen 5y ago
      Hurricane Katrina was quite recent, it devastated a major American city and had all sorts of bad effects in lots of places, people have an intuitive understanding of how big Hurricane Katrina was - be aware of course that intuitive understandings are not precise.
      - Ratiofarmings 5y ago
        As a non-American, I have no idea what kind of damage hurricane Katrina did. As far as I am concerned, there was some wind. Enough to make international news, but that's about it. But when I see "comparable to a nuke" at least I know immediately that this is a major event. A hurricane, powerful as it may be, is harder to grasp for a comparison.
        bryanrasmussen 5y ago
        >As a non-American, I have no idea what kind of damage hurricane Katrina did As a non-American, I do. I agree comparable to a nuke is better, I was just commenting that Katrina for a large number of people is quite different than the other examples and does convey an intuitive understanding. While noting that intuitive understandings are imprecise.
      - throwaway0a5e 5y ago
        The math might check out but that's about it. Comparing a storm to an explosion is completely asinine because the mechanism by which the energy is dispensed is completely different. Katrina did squat to the city except tear up some roofs and windows. The water deposited just so happened to breach some flood control stuff and then all the damage was a result of everything being immersed in floodwater. A storm releases energy in the form of find and droplets of liquid being accelerated by gravity and flung around by said wind. An explosion releases a pressure wave. Comparing energy released in storms to explosions is like saying a leafblower can push harder than a dude with a sledge because it has more horsepower. Neither comparison serves any useful purpose.
avn2109 5y ago
I'd be happy with a total energy measurement in some multiple of Joules, or maybe in megatons of TNT.

Taek 5y ago

Even though the damage types are not analogous people still want a crude metaphor for how "big" the blast was. Since people are going to compare it to a nuke regardless you might as well have some rough criteria for how a comparison could happen.

kshacker 5y ago
Why are people going to compare to a nuke? Because the media uses those terms. Maybe we need to suggest alternatives. Also since 1945, had there been just a single size of nukes? I may not have a sense of how big a Hiroshima nuke was as compared to a 1975 nuke vs a 2022 nuke. Just saying ... a better comparison (which I don't know as I am not a subject expert) could be developed. Maybe "enough energy to melt 1980 Antarctica" or some other similar scary comparison. Maybe "10 times the energy of hurricane Katrina" Edited the last 3 words
- Jabbles 5y ago
  But those other examples suffer from the same flaw that no one has any intuitive understanding of how big those events are. - Tonga eruption was 1e7 tons - Hurricane Katrina was 1e10 tons - Melting Antarctica is 1e12 tons (afaict)
  - bryanrasmussen 5y ago
    Hurricane Katrina was quite recent, it devastated a major American city and had all sorts of bad effects in lots of places, people have an intuitive understanding of how big Hurricane Katrina was - be aware of course that intuitive understandings are not precise.
    - Ratiofarmings 5y ago
      As a non-American, I have no idea what kind of damage hurricane Katrina did. As far as I am concerned, there was some wind. Enough to make international news, but that's about it. But when I see "comparable to a nuke" at least I know immediately that this is a major event. A hurricane, powerful as it may be, is harder to grasp for a comparison.
      - bryanrasmussen 5y ago
        >As a non-American, I have no idea what kind of damage hurricane Katrina did As a non-American, I do. I agree comparable to a nuke is better, I was just commenting that Katrina for a large number of people is quite different than the other examples and does convey an intuitive understanding. While noting that intuitive understandings are imprecise.
    - throwaway0a5e 5y ago
      The math might check out but that's about it. Comparing a storm to an explosion is completely asinine because the mechanism by which the energy is dispensed is completely different. Katrina did squat to the city except tear up some roofs and windows. The water deposited just so happened to breach some flood control stuff and then all the damage was a result of everything being immersed in floodwater. A storm releases energy in the form of find and droplets of liquid being accelerated by gravity and flung around by said wind. An explosion releases a pressure wave. Comparing energy released in storms to explosions is like saying a leafblower can push harder than a dude with a sledge because it has more horsepower. Neither comparison serves any useful purpose.

avn2109 5y ago

I'd be happy with a total energy measurement in some multiple of Joules, or maybe in megatons of TNT.