Ship spies largest underwater eruption ever | Hacker News Reader

Ship spies largest underwater eruption ever

sciencemag.org

112 pointsFifth_Star35 comments

It's interesting to read an article and come to HN hoping to find more interesting comments only to find one thread with stupid memes.

Is this the largest ever because we're just starting to be able to map this type of stuff or have we seen a lot of them and this is enormous?

Well there is this, "The map of the sea floor, made by the ship’s multibeam sonar, indicates that as much as 5 cubic kilometers of magma erupted onto the sea floor."

I think 5 km^3 is a large eruption by any standards. Looking at lists of modern ones it's a index 6 event which happen every few decades on land. From the article it sounds like if it weren't close to Mayotte it wouldn't have been picked up seismically.

... gas trapped inside the black volcanic material.

Sudden release of such gases has been suspected in the case of a number of sudden ship disappearances over the centuries. If a bubble's volume is large relative to the ship's, the ship will drop to the bottom as the gas forces water from under the hull. Then the surrounding seas crash onto the decks.

There is a no-sail zone quite near the coast of Grenada due to an active underwater volcano. The volcano is called Kick 'em Jenny and has sunk numerous boats over the years. On one instance it sunk a boat and killed 60 people.

Wikipedia link for the lazy https://en.wikipedia.org/wiki/Kick_%27em_Jenny#Maritime_excl... The part about the "sinking hazard" has a [citation needed] anyway. The Spanish version look more concerned about eruptions than bubbles, and says that when they detect unusual activity the radius is increased from 1 mile to 3 miles.

Well that about wraps up the Bermuda Triangle for me

Bubbles that large are not stable—the sinking effect (which is disputed) would have to do with a significant reduction in density of the water by a large number of smaller bubbles.

Try to picture this. All the water next to a ship mysteriously flowing away from the ship, over the bubble while the ship for some reason is the only thing going down through it.

Water is also heavier than air, and water on top of a bubble will also fall into the center of the bubble (breaking it up into smaller bubbles), until the surface tension of the water around the bubble is great enough to hold it together (small bubble).

Therefore a huge bubble gets split into many bubbles, I suppose at depth a lot of the gas gets dissolved into the water. The worst that would happen is many small bubbles cause the density of the water to decrease, causing the boat to sink lower into the water. I'm not sure if the water could lose enough density to sink a regular boat directly?

I think what you may be thinking of is large, shallow explosions (generally man made) under a ship which create a temporary bubble which then collapses in on itself, but can cause extreme stress on large ships.

Extremely contrived example of bubbles being able to sink a small boat: https://www.youtube.com/watch?v=MSmAXp_BHcQ

How a bubble generated by an explosion can actually sink a large ship: https://youtu.be/UdFNuc5XtII?t=192

is this too deep for a tsunami effect? can underwater volcanoes cause tsunamis?

The article says it’s too deep to cause a tsunami, at least where the quakes are now. If seismic activity starts moving towards land and a big quake is close enough, a shelf-collapse could cause one.

That would be scary, seeing as I believe the largest tsunami ever was created via a similar mechanism.

Edit: not the largest, but large. See: https://en.m.wikipedia.org/wiki/Storegga_Slide

I read that headline as "Ship spies largest underwear eruption ever"

I can't even say where my mind went, 'cause it hasn't come back yet...

Fridays are hard. Especially on mobile screens.

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