[HN Gopher] More than 19k undersea volcanoes discovered
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More than 19k undersea volcanoes discovered
Author : tamaharbor
Score : 124 points
Date : 2023-04-22 01:55 UTC (21 hours ago)
(HTM) web link (www.science.org)
(TXT) w3m dump (www.science.org)
| dataflow wrote:
| > In 2005, the nuclear-powered USS San Francisco collided with an
| underwater volcano, or seamount, at top speed, killing a crew
| member and injuring most aboard. It happened again in 2021 when
| the USS Connecticut struck a seamount in the South China Sea,
| damaging its sonar array.
|
| How in the world does a submarine going at < 40 mph not detect
| that it's running into a mountain? Why are light, radar, and
| sonar still not enough to detect obstacles that big?
| gonzo41 wrote:
| Most underwater travel is done via dead reckoning. Like flying
| a plane with no windows. You're only as good as your maps and
| instruments.
| miketery wrote:
| Maybe they're off for stealth?
| vkou wrote:
| You can't navigate by light, and if you are trying to be
| stealthy, you won't be running active sonar. Radar doesn't work
| well underwater.
| indymike wrote:
| Easy way to not be found is to not emit energy be it sound,
| heat, light, radio frequency, etc... until we discover a
| passive sensor that works underwater that can see static
| objects that may not emit energy, seamounts and other things
| that change the map are occupational hazards for submariners.
| perfmode wrote:
| how deep do submarines cruise?
| dragonwriter wrote:
| The _San Francisco_ collided with the seamount at 160m depth.
| nahnahg wrote:
| Because they are too stupid to use large aperture (and pressure
| stabilized) plain old optics with CCD sensor array.
|
| I assume this is done actually. If fish can do it at the
| greatest depths then...
| dragonwriter wrote:
| > How in the world does a submarine going at < 40 mph not
| detect that it's running into a mountain?
|
| Seamounts don't give off active emissions (except maybe if they
| are erupting), and subs usually use passive hydrophones (which
| rely on the active emissions of targets), not active sensors
| when operating underwater to avoid detection.
|
| Navigation is done by charts using inertial navigation
| alongside dead reckoning. Hitting a mountain is generally
| because the mountain wasn't on the chart being used, though in
| principle in could also be due to an error in positioning (with
| inertial navigation, that should be much rarer than with dead
| recknoning alone, but its not impossible.) (In the case of the
| _San Francisco_ , for instance, other charts had a notation of
| "discolored water" which suggested a probable seamount, which
| the investigation noted should have been transferred to the
| chart in use, but was not.)
|
| > Are light, radar, and sonar still not enough to detect
| obstacles that big?
|
| Radar is useless underwater, light would also be useless for
| spotting anything in time to react at speed, and sonar isn't
| routinely used because it compromises stealth.
| amelius wrote:
| > and sonar isn't routinely used because it compromises
| stealth.
|
| Can't they use the same frequency/waveform as whales?
|
| Or a different question: why don't whales routinely hit
| underwater volcanoes?
| hguant wrote:
| Couple of different answers to these questions:
|
| a) whales don't tend to go where volcanos are. Whales dive
| to find food, and their food sources aren't near the
| seabed. I think the deepest diving whale species are sperm
| whales, and they go after squid, which are not typically
| found near volcanos.
|
| b) it's not a question of matching frequency with the
| whales, it's a question of noise emissions and the amount
| of energy you're putting into the water. Modern active
| sonar systems are incredibly energy intensive, and the
| technology to modify the waveform and limit the power of
| the waveform to match something biologic doesn't really
| exist, and would have to justify all the added complexity
|
| c) USN and US geological survey charts are really really
| good, and regularly updated, to the point where "It wasn't
| on the charts!" is a claim met with extreme skepticism. 9
| times out of 10 some sort of navigation or systemic error
| was involved.
| matheusmoreira wrote:
| > Hitting a mountain is generally because the mountain wasn't
| on the chart being used
|
| How could it not be in the chart though? Is the ocean not
| fully mapped?
| Wronnay wrote:
| No, the ocean is not fully mapped. It's written in the
| article: "With only one-quarter of the sea floor mapped
| with sonar, it is impossible to know how many seamounts
| exist."
| dragonwriter wrote:
| > How could it not be in the chart though?
|
| In the specific case of the _San Francisco_ , because
| notations indicating a probable seamount were not
| transferred from other charts when the chart being used was
| compiled; there is some lack of clarity on how much the
| failures involved are the responsibility of the command
| crew of the sub and how much of higher command, but its
| definitely a failure to appropriately use existing
| information, not a "the information did not exist" problem.
|
| While the area was apparently not well charted, the
| responsible crew not using the information at hand
| (including information as to the the quality of charting
| data for the area) was also apparently at play in the
| _Connecticut_ grounding.
| throwaway8503 wrote:
| >> Are light, radar, and sonar still not enough to detect
| obstacles that big?
|
| > Radar is useless underwater, light would also be useless
| for spotting anything in time to react at speed, and sonar
| isn't routinely used because it compromises stealth.
|
| Any people with knowledge in the field care to comment on
| whether it's feasible for a light (em?)-type, active, near-
| range detection system to work?
|
| It seems to me the basic problem is:
|
| - enough energy to get a signal at a range sufficient to move
| around any detected obstacles
|
| - high enough dissipation in water to minimize range at which
| detection by external sensors is possible
| iancmceachern wrote:
| The light transmission through the water, it's cloudiness,
| is just way to variable for something like this to work
| constantly, reliably.
| throwaway8503 wrote:
| Wouldn't the cloudiness itself be a signal?
|
| Presumably it's essentially clear of suspended particles,
| most of the time.
| iancmceachern wrote:
| A signal of what?
| throwaway8503 wrote:
| Something solid ahead
|
| To clarify: I mean that, generally speaking, the presence
| of 'cloudy' water would presumably signify that the
| seafloor was close. In the open ocean, maybe a sea mount
| is surrounded by essentially a cloud of particles.
|
| Edit: I think your reply made the thread reach maximum
| depth, so I'll end it here.. I should do more reading on
| the topic.
| iancmceachern wrote:
| The problem I'm highlighting is it also gets cloudy
| randomly in open ocean, for lots of other reasons.
| iancmceachern wrote:
| The issue is that the cloudiness of water, even open
| water, varies greatly. So there would be either lots and
| lots of false positives, or the system would be too
| insensitive.
|
| Think driving in fog
| robbiep wrote:
| Have you ever dived? Max visibility is like 30-50m unless
| you're in a filtered environment
| gamblor956 wrote:
| Your two requirements contradict each other. You can choose
| one or the other, but not both.
|
| The world's militaries have invested a great deal of time
| and money into researching underwater sensors. The solution
| is not going to be discovered by random people on the
| Internet.
| skinkestek wrote:
| > The solution is not going to be discovered by random
| people on the Internet.
|
| I'm fairly certain someone knows a number of things that
| have been discovered by random people on the internet.
| dragonwriter wrote:
| > Any people with knowledge in the field care to comment on
| whether it's feasible for a light (em?)-type, active, near-
| range detection system to work?
|
| I'm not in the field, but I follow it enough to say: in
| theory, yes, (blue-green lidar), and there is a lot of work
| on moving this from theory to practice.
|
| But approximately _everyone_ is working on it (for
| bathymetry and for detecting subs, and similar blue-green
| laser tech for underwater comms), so its likely once its
| deployed so that a sub _could_ in principle use it as a
| "headlight", it'll raise similar concerns to sonar, because
| if it is used actively, passive sensors looking for active
| use will also be common.
| simonebrunozzi wrote:
| the issue is to detect these while maintaining stealth.
| dexwiz wrote:
| Water absorbs photons at most frequencies outside the
| visible spectrum. What we deems as visible light is
| actually where water is most transparent. Since eyes
| evolved underwater, it makes sense they would use this
| section of the spectrum.
|
| https://commons.wikimedia.org/wiki/File:Absorption_spectrum
| _...
| jvanderbot wrote:
| That makes so much sense and actually unravels a few
| other mysteries for me. Thanks!
| hilbert42 wrote:
| _" Radar is useless underwater."_
|
| But sonar and detecting changes in gravity (caused by the
| higher density of the seamount) aren't.
|
| The seamount should have been detectable.
| adastra22 wrote:
| There's no way you could have gotten a gravity sensor to
| work reliably enough in that environment. Active sonar
| would defeat the point of a stealth submarine.
| hilbert42 wrote:
| Is that an assumption or do you know from fact?
|
| Gravity detectors work from moving aircraft (it's a
| common method of deployment), so motion's no problem and
| can be made incredibly sensitive--sensitive enough to
| suit the job in hand (place one on a table and then on a
| book on the table and you'll easily read the difference
| in gravity). Moreover, seamounts are incredibly large
| objects and would have huge signatures and thus easy to
| detect.
|
| I'd suggest the real issue around this matter is that
| it'll be classified.
| abecedarius wrote:
| What's the technical term for this type of gravity
| detector? Do you mean a gravity gradiometer? It seems
| hard to steer a modern pigheaded search engine away from
| LIGO when you search for "gravity detector".
| dragonwriter wrote:
| Sonar is a brilliant beacon identifying the subs location;
| other than in combat where they are already detected or
| desperately need a hard fix on a target _now_ , or
| someplace they don't need to be stealthy, subs aren't using
| it.
|
| AFAIK, the first sub-deployed gravity gradiometers were
| developed for the _Ohio_ -class ballistic missile subs and
| _Los Angeles_ -class attack subs like _San Francisco_
| don't, AFAIK, have them.
| catminou wrote:
| I recall looking at the various charts and from what I recall
| the "discolored water" notation was sourced from a chart
| several decades before and was offset by a few miles
| (incorrectly charted in the first place).
| kyriakos wrote:
| Naive suggestion from someone who has zero knowledge about
| these things: can't an unmanned submarine drone be constantly
| moving ahead of the main submarine to detect these obstacles
| before they become dangerous to the submarine and crew?
| theelous3 wrote:
| Even worse than letting an enemy know where you are now, is
| letting them know where you will be in the future.
| rdl wrote:
| Best solution is to pre-map the ocean to the degree
| possible (mountains don't tend to move, at least on the
| timescales we care about...); this wouldn't need to be done
| stealthily (so you could use active sensors), and using
| surface ships is one option, also drone surface ships and
| drone underwater vehicles now. I assume there are
| relatively highly classified high-detail government maps of
| certain parts of the ocean of particular interest.
|
| We also have highly classified models of the exact shape
| and mass distribution of the Earth, as this is essential to
| accurate long-range ballistics (i.e. for ICBMs to hit their
| targets) -- it affects the gravity experienced over the
| course, and the precision/accuracy needed is higher than
| just uniform-density sphere or oblate spheroid. Also of
| magnetic and other anomalies since that can be used as a
| baseline when searching for submarines or ships using
| magnetic sensors, although I think this is less important
| now.
| michelb wrote:
| How many decades/centuries would it take to map the
| ocean?
| dragonwriter wrote:
| Its already been largely done, which is why when subs run
| into seamounts, you tend to see the leadership team
| relieved.
|
| "Maybe it would help to have a map of the space we're
| going to be driving very large, very expensive,
| strategically important pieces of equipment (that also
| have crews) through blind" is not, as it turns out,
| something that never occurred to the Navy.
| tomrod wrote:
| Oceans cover 361M km^2. So if we built 13,333 drones with
| a failure rate of 25% and they map at a rate of 50
| km^2/day at a higher column depth with active sonar, it
| would take approximately 2 years
| cagenut wrote:
| https://www.youtube.com/watch?v=83FQzfH_r2U
| tomrod wrote:
| There you go.
| ipaddr wrote:
| It sounds like the Human Genome Project. Well worth the
| effort.
| swayvil wrote:
| Also speaking from utter naivety, this seems like a super
| good idea. Each submarine gets a little attendant
| constellation of drones. Control them with Bluetooth. Or
| usb cables.
|
| Or whiskers! That's how cats and catfish do it. A dozen
| 300' plastic prongs protruding frontward.
|
| Or, to combine the two : TENTACLES!
| amelius wrote:
| Nice idea, but how many ship-lengths does a submarine
| need to slow down from full to zero speed? Probably more
| than a few.
| Loic wrote:
| Yes, but noise would be a problem.
| kyriakos wrote:
| Noise from the drone propeller?
| hyperthesis wrote:
| Wouldn't a small drone make less noise than a submarine?
| jvanderbot wrote:
| That seems intuitive but one thing I've learned in my
| career is that obvious easy ideas that nobody does are
| usually missing key details.
| dragonwriter wrote:
| A small drone and a submarine would make more noise than
| either alone.
| bheadmaster wrote:
| What about using a pressure sensor fixed to a long pole
| in front of the submarine? That way, if they hit
| anything, the pole would hit first, and could activate
| the stopping mechanism.
| hutzlibu wrote:
| Imagine swimming with a long pole attached to the front
| of you. Even if it would be thin, it would still disturb
| you very much. Also the disturbances in the water created
| by the pole would make noise, that can be detected.
|
| Submarines are optimised in everything for absolute
| stealth, up to the point that the crew may not make any
| noise, like dropping a wrench.
| adastra22 wrote:
| These things can't stop on a dime.
| bheadmaster wrote:
| How long would the pole have to be to stop a 40mph
| submarine?
| adastra22 wrote:
| You could probably find the data you need here:
|
| https://core.ac.uk/download/pdf/36725639.pdf
| nonethewiser wrote:
| How would it communicate stealthily?
| theelous3 wrote:
| It wouldn't because it wouldn't be stealthy.
| kyriakos wrote:
| Why does everyone assume you need wireless communication?
| You can have a cable running between the submarine and
| the drone, same channel would be used to power the sub.
| swayvil wrote:
| Like a Medusa. Submarines would get scarier.
| lazide wrote:
| That is a lot of heavy, droopy, cable (if it is going to
| be able to withstand the stresses and 'unkindness' of the
| ocean) which is very likely to get tangled in things like
| spinning propellers unless very carefully managed.
|
| Also, fishing trawlers, whales, etc.
| mywacaday wrote:
| How viable would drones travelling in front of the sub like the
| whiskers in the TV show seaQuest DSV
| capableweb wrote:
| One of the main features of military submarines is being
| undetectable by others, to various degrees. This include
| visual, audio and movement detection. Drones would probably
| make all of those three factors worse and make the submarine
| more detectable, than without a drone travel in front.
| DrBazza wrote:
| > How in the world does a submarine going at < 40 mph not
| detect that it's running into a mountain?
|
| Two things: first US submarine, second "South China Sea". I
| suspect the sonar was off "for reasons".
| hilbert42 wrote:
| The USS San Francisco crash-type problem was discussed some
| while ago on HN. At the time I questioned how this could happen
| when one would expect a submarine of that sophistication to be
| equipped with both sonar and gravity detection.
|
| Detecting changes in gravity is common practice in mining
| surveys (ores often have higher densities) and geological work,
| so for me why the sub collided with the seamount remains a
| mystery.
|
| I cannot believe subs of this class don't have such detection
| on board so could someone more knowledgeable about the subject
| than me provide an explanation.
| [deleted]
| whitemary wrote:
| Is every seamount a volcano?
| adastra22 wrote:
| What else would they be?
| Ekaros wrote:
| Probably not. I would think that similar to above water
| formation, there is also at least three ways mountains happen.
| Volcanic, folding(two plates collide) and Block.
| Scubabear68 wrote:
| It has always boggled my mind that military subs run around under
| the water largely blind, due to the fact that using active sonar
| would give their position away, and passives are going to miss
| many things like this.
| alejohausner wrote:
| Here is the data:
|
| https://zenodo.org/record/7718512
| richardfey wrote:
| A map would have been nice there
| SV_BubbleTime wrote:
| In what might be a stupid question...
|
| Do underwater volcanos release CO2 when erupting?
|
| I assume it would be yes, and that eventually bubbles would reach
| the surface.
|
| But, could imagine a scenario where the gas is absorbed before
| reaching the surface?
| edmundsauto wrote:
| The San Francisco struck it at 160m depth, I am also curious to
| this question. 1km, sure I doubt we see bubbles - but 160m is
| not as deep (and the bubbles would get bigger in volume as they
| rise). Great question, does anyone know?
| ycombinete wrote:
| _"From the ocean surface to depths of about 500 meters CO2
| would exist as a gas and would tend to rise in the water
| column, since it is less dense than seawater. Between 500
| meters and 2,700 meters CO2 would exist as a liquid, but one
| that is still lighter than seawater and would thus also rise in
| the water column. At depths up to 2,700 meters CO2 will create
| a rising plume and dissolve into the surrounding seawater
| relatively quickly.
|
| At depths deeper than 3,000 meters the weight of the water
| column compresses the liquid CO2 and it becomes denser than
| seawater and sinks slowly to the seafloor."_ [0]
|
| So yes, even at normal temperatures for that depth C02 would be
| a gas; definitely so at volcanic temperatures!
|
| [0] https://maritime-executive.com/features/ocean-storage-of-
| co2
| [deleted]
| wilg wrote:
| I'd have been impressed with just one!
| Xelom wrote:
| Then does this mean these volcanoes will slowly shrink the size
| of the ocean which might contribute to raising sea levels on top
| of melting glaciers?
| pulvinar wrote:
| It would be extremely unlikely. Instead, it should be close to
| equilibrium, with as many eroding away as being created.
| 1propionyl wrote:
| Wouldn't erosion tend to lag exposure by something like an
| order of magnitude or five? Geological time vs climate time.
|
| That said, I'd also point out that most of these are deep
| enough we wouldn't see them exposed even if ocean levels
| dropped a meter worldwide.
| codybontecou wrote:
| Wouldn't it just displace the water?
| theelous3 wrote:
| Yes? That is exactly the commenters concern. Fill a bowl to
| the brim with water, throw a ball in. It spills over the
| edges of the bowl by "just displacing" the water.
| louthy wrote:
| Surely the magma, once cooled, would take less physical space
| than when hot?
| colechristensen wrote:
| No.
|
| Land moves around, raises and lowers, plates crash lifting
| mountains and subduct continents under each other so stuff
| _moves_ , but stuff goes up and down at the same time.
| Sometimes the land sinks, sometimes it's pushed up, but these
| geological processes happen on geological time. Sea level rise
| is a concern within a few human generations.
|
| These are just much different time and volume scales.
| Ekaros wrote:
| That is quite many, if you start to think spacing them, 19000km
| if they were 1km apart on average... Then again, there is lot
| more fault line distance on Earth.
| Tepix wrote:
| From tfa: " _the team can detect seamounts just 1100 meters tall_
| "
|
| This really gives you an idea how poorly the ocean floor is
| mapped.
| jl6 wrote:
| Do these volcanoes really have steep/craggy dramatic slopes like
| the image suggests?
|
| I remember being disappointed to find that the Mariana Trench
| didn't have looming near-vertical canyon walls, but rather had a
| relatively tame slope.
| DrBazza wrote:
| > Do these volcanoes really have steep/craggy dramatic slopes
| like the image suggests?
|
| Probably not many. They will have formed slowly at plate
| boundaries such as the mid-Atlantic ridge, then moved apart
| over millions of years, then very, very, slow erosion.
|
| > I remember being disappointed to find that the Mariana Trench
| didn't have looming near-vertical canyon walls, but rather had
| a relatively tame slope.
|
| One of my favourite books mentioned that you could easily drive
| a car to the bottom of the Marianas trench if it were dry
| (https://seabedhabitats.org/2015/08/26/book-review-mapping-
| th...).
| marcellus23 wrote:
| Wow, I did some googling and found this cross-section of the
| Mariana Trench. Was not expecting this at all (bottom of the
| page, figure 4):
| https://mason.gmu.edu/~bklinger/deeptrench.html
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