Satellite data reveal nearly 20k previously unknown deep-sea mountains | Hacker News Reader

Satellite data reveal nearly 20k previously unknown deep-sea mountains

sciencenews.org

172 pointsBrajeshwar60 comments

I'd love to see more satellite-based underwater archaeology, seeing how far sea levels rise after the last glacial period. A lot of human history is probably out on the continental shelves.

See, for example, Doggerland beneath the English Channel: https://en.m.wikipedia.org/wiki/Doggerland

More aerial Lidar-based archeology would also be pretty cool.

It seems that there was a strong momentum in that direction a few years ago but recently I’ve stopped hearing about it (or at least not that often compared to the recent past).

LIDAR has made a splash in archaeology last few years, especially in South America where the jungles cover up all the ruins. See [1][2][3] etc

You haven't heard much about it because everyone is scrambling for funding to go excavate these ruins in person.

[1] https://www.nationalgeographic.com/history/article/maya-lase...

[2] https://www.thearchaeologist.org/blog/lidar-technology-confi...

[3] https://arstechnica.com/science/2021/10/lidar-reveals-hundre...

It's not probably out there, it's definitely out there. One of the absolute best places to be a hunter gatherer is in river deltas and low lying floodplains. If we could magically lower sea levels by 100m, we'd find evidence of humanity not only in doggerland but off the coast of Africa, China, Australia, and more.

In fact some archaeologists are planning future underwater digs based on today's topographical hints of ancient riverbeds now underwater. There's a massive one off Bengal, another one near Ceylon, and a few more I can't remember right now.

Could these places be a source for gold? Were these cultures advanced enough to be mining and smelting gold?

So, your first thought when searching for artifacts from the ancient past is whether they can be melted down into commodities?

A more charitable interpretation of the comment that you replied to is that the artifacts may be located near ancient gold mines, and after we've retrieved the artifacts during excavation then we could potentially continue to mine the valuable resources in the same location.

Erm, just no and that wasn't necessary, or GPT?

I think GP might've been sarcastic, but even if not, there's no need to be charitable to such a caricaturistic intent to extract resources.

Any implication that archaeologists are remotely interested in gold or that there's monetary profit to be had from excavations is almost always destructive to the cause of heritage programs.

I've done anti-looting programs in various places around the world as part of excavations. The belief that gold and other precious artifacts will be found is one of the most common causes/justifications for looting. Moreover, the belief that archaeologists are motivated or will in any way help to find precious metals is utterly corrosive to our ability to work with local authorities because it reduces trust and incentivises preemptive looting whenever we show up, among other things.

Let me emphasize this: finding precious metals sucks. It means you have a lot more paperwork, it means you get a lot more looting, it means a lot of government interest, it means treasure hoard laws apply, future excavation decisions become far more political, etc. It's a massive pain in the butt all around.

> I've done anti-looting programs in various places around the world as part of excavations.

This sounds fascinating, do you know of anywhere I can read about this kind of work?

It's way more boring than you're thinking. The goal is to reduce looting by

1) educating people about the harm it does

2) convince the audience that whatever goals might be sought in looting are unlikely to be met (profit, cool-stuff-factor, "helping archaeologists", etc)

3) Ensuring site security and getting legal frameworks in place to monitor/enforce heritage preservation.

The first is usually pretty easy. The NPS used to have this video called "Assault on Time" that they show to people. People who don't want to fill out requisition forms from the government usually just show pictures of looted sites. I had a professor who liked to use pictures of Mimbres sites in New Mexico. I prefer to use Ai-Khanoum because the before [0] and after [1] is so stark.

For the second, usually this takes the form of inviting locals out to see what you're excavating and showing them any finds. This will usually be rocks, charcoal, lithics, and other profoundly unprofitable things. It also humanizes the historical people to help locals build personal connections with the sites. In a lot of cases you'll also be hiring locals to help with the excavations, so they know there's nothing hidden because they're present for everything.

This usually isn't effective on the "collectors" and "metal detectorists" (see e.g. Coping with Site Looting [2]), so other things are necessary. That tends to be site monitoring and heritage protection laws, which depend on the country and situation. Sometimes it's best to just invite local officials to the site. Meeting with important officials can be very inconvenient though. Ever tried getting wrinkles out of a suit in a field site 2 days from the nearest city? Those clothes did not survive the expedition.

That's just the lowest level of cooperation that has to happen as well. The key is having embedded experts making connections with the people who can implement those laws and fines, then enforce them. This is also the level most affected by the budgetary constraints of heritage programs globally. Last I checked, there were fewer than 100 positions for this sort of work available in the US every year. Some countries may have less than a dozen people total.

[0] https://en.wikipedia.org/wiki/File:Ai_Khanoum_landscape_phot...

[1] https://m.psecn.photoshelter.com/img-get/I0000lqdxnldw3QE/s/...

[2] http://npshistory.com/series/archeology/seac/rapp/1.pdf

They definitely would be a good place to search. Not only for historical artifacts but becuase the plains would trap the heavier gold flakes that got eroded either locally or upstream.

For instance the state of Pennsylania has no known gold vein deposits but small flakes of gold are often found in the rivers, since the quartz rocks that contained the flakes were eroded, freeing the flakes which are then washed into the river by rain.

We know very close to nothing about them, so the answer to most such questions is "maybe".

No. These areas were not flooded overnight. It took many years. Any valuable items would have been taken as people moved ahead of the very very slowly rising water. Your chances would be little different than finding gold randomly on dry land.

I used to lifeguard on a beach in Ireland, on a very low tide and if the sand had shifted there were solid black slimy things just under the sand, turns out they were the remains of an ancient oak forest, would be amazing to see what 100m would should, that was only 3-4 meters.

Do you think we will discover some frequency of light that will let us map the ocean floors as you imagine?

AFAIK there are no frequencies of the electromagnetic spectrum we are not aware of, but our techniques and signal processing can potentially improve. There are also frequencies of waves other than light that we can use, such as sonar - but not from a satellite of course.

> there are no frequencies of the electromagnetic spectrum we are not aware of,

How would we know if we aren’t aware of them though?

Well, where would these hypothetical frequencies exist in the spectrum?

It's not really about the frequency of light. We pretty much have "discovered" all frequencies -- it's the electromagnetic spectrum. We know all of the frequencies that exist. The trick is devising new methods with increasingly sensitive instrumentation.

This article talks about how researchers looked at measurements taken from space to gauge where the sea level was a mere few-centimeters higher than the surrounding area! Incredible! In theory, I could have seen someone like Arthur C. Clarke proposing this half a century ago - but with the precision in instrumentation only becoming available today, the idea could have been proposed long before the technology existed.

In the future, might we devise a method and accompanying instrumentation that will allow us to map the sea floor with just a regular flash light hung from a ship? Maybe (but probably not). Point being: It's the methodology + instrumentation, not the frequency of light itself.

My wording was off. It is not trivial to measure or generate each frequency of light! So, new technologies that could enable satellite-based mapping of the sea floor would likely rely on the development of frequency specific sensors. And, as was pointed out, perhaps new ways of measuring and generating specific frequencies of audio.

Gravity is already used for mapping and for oil exploration. I dont know all of the details but there are quantum gravity sensors that are meant to be very accurate, which I assume could be used for mapping.

Sea floor is usually mapped in the audio spectrum: https://oceanexplorer.noaa.gov/explorations/lewis_clark01/ba...

Another example: the underwater structures off the coast of Cuba

https://en.m.wikipedia.org/wiki/Cuban_underwater_formation

At 600+ meters of depth, those are almost certainly not of human origin. There are many examples of these sorts of phenomena, which derive their regular shapes from the way crystalline minerals fracture.

I am curious now - at what depths is it considered human origin? Is it because we know how much the sea level has risen in the last x years?

During the last glacial maximum 20,000 years ago the sea level was about 130 meters below today's [1] so agriculture would be found above that. About a hundred thousand years before that sea levels were close to modern levels and the current ice age [2] started almost half a million years after the first stone industry [3] got started, so sea levels would have been much higher (200-300 meters higher than today).

[1] https://en.wikipedia.org/wiki/Past_sea_level

[2] https://en.wikipedia.org/wiki/Quaternary_glaciation

[3] https://en.wikipedia.org/wiki/Oldowan

Is there any additional potential wiggle room for local uplift/erosion/etc over time, in some areas, or is that mostly a rounding error?

Yes. But 600 meters? That seems very unlikely.

Well to be pedantic there wouldn't be any agriculture found at those depths, unless we have prehistory very, very wrong. Which is possible, and one reason why it would be good to check!

Fun fact: That's actually the real world location of Kree City [1] from the Marvel franchise. However, they had to film in Puerto Rico and show the city entirely via CGI for the Agents of S.H.I.E.L.D. due to the Cuban embargo and Skye flooding the city before the spec ops camera crew could get there.

[1] https://marvelcinematicuniverse.fandom.com/wiki/Kree_City

Dupe: "More than 19k undersea volcanoes discovered"

https://news.ycombinator.com/item?id=35662580 (134 points | 9 days ago | 92 comments)

Here's a link to the original article (open access) with figures and all that: https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/202...

My favorite part of the article is the mention of the submarine hitting an uncharted sea mount. I rarely think about the fact that they can't just leave sonar on at all times to be aware of their surroundings and often rely on known mapping data.

But why submarines do not have a tethered drone traveling I don’t know, 1 mile ahead of them and hit such obstacles?

Cost and complexity is probably one part of it.But more importantly, I imagine having a drone ahead of them would generate noise, thus decreasing stealth.

It's probably one of those things that shouldn't happen if you're doing everything else the "right" way.

It would not be trivial to design an separate underwater vehicle that could travel ahead of a submarine at flank speed (>30 knots), let alone do so quietly.

Why not exactly? Due to stealth or some other reason?

Stealth is a big component. Also, Sonar is known to impact marine life

I believe there are Sonar bouys that are toed behind ships to detect submarines. These could be used, and I would guess that these are used to map the sea floor, but the sea is so flipping big that there are still unmapped areas. But I'm not an expert and would defer to an actual expert (or ChatGPT)

Active sonar (where a device sends a pulse of energy & listens to replies) can impact marine life.

Passive sonar (where you just listen to acoustic energy in the water) is used by submarines and surface ships to find submarines. With both on-board and towed sonar.

Submarines don't have any sonar designed to map the sea floor, though there are tools to identify the depth below the keel at any given time. Creating proper maps of the sea floor are done by much more specialized equipment/systems/processes. https://en.wikipedia.org/wiki/National_Geospatial-Intelligen...

(former US submariner here)

Also commented downthread, but sonar IS always on at all times. https://news.ycombinator.com/item?id=35780124

Honestly, I'm extraordinarily surprised that the USS San Francisco didn't sink killing everyone onboard. Have you seen the photos? https://en.wikipedia.org/wiki/USS_San_Francisco_(SSN-711)#/m...

The only reason that the submarine was able to get to the surface and stay there after this was because the damage was just on the port (left) side. Even with that luck, they were only able to stay on the surface because a piece of equipment was able to stay running for several times longer than it was designed to do.

You can read more about it in various places (like here: https://nationalinterest.org/blog/reboot/what-happens-when-s... ) but imagine being at work and suddenly getting thrown toward a wall at 20++mph. Damages and injuries everywhere, and its a miracle only one person died.

>but sonar IS always on at all times

Yeah completely forgot there is both active and passive sonar.

> the researchers looked for centimeter-scale bumps caused by the gravitational influence of a seamount

Remarkable and even puzzling on two counts:

1) Gravity is so weak at human scales we tend to forget that each and every body leaves a gravitational imprint. Yet a mountain sized mass creates detectable influence.

2) Centimeter-sized height sea level differences are detectable from space. Pressumably this integrates over long periods of wave "noise" and tidal swells that are significantly higher than a centimeter...

"Most of the newly discovered underwater mountains are on the small side — between roughly 700 and 2,500 meters tall". 2500 meters is small? Even 700 meters is almost as tall as the Burj Dubai. I'd call 2500 meters a decent sized mountain.

You may enjoy the movie The Englishman Who Went Up a Hill But Came Down a Mountain.

Depends on your point of reference though; the lowest lying lowland is around 3600m "tall" when measured from average ocean floor depth rather than sea level, and a 2500m seamount might be sitting in a valley surrounded by the underwater edges of continental shelf that's at least twice as high as it. By our usual standards, they're -1000m tall :)

If you're in a submarine that is only 10m tall, 700m is huge. It seems like a pretty good idea to know where they are

> However, it’s possible that some could pose a risk to mariners. “There’s a point when they’re shallow enough that they’re within the depth range of submarines,” says David Clague, a marine geologist at the Monterey Bay Aquarium Research Institute in Moss Landing, Calif., who was not involved in the research.

It would be interesting to see what proportion of these 20k deep-sea mountains were actually known to either the US or Soviets as part of their submarine support.

Knowing the location of these deep-sea mountains could be very valuable when you are engaged in submarine cat and mouse games with nuclear submarines.

My guess is that quite a few were known but classified as a national security matter.

Here is the data: https://zenodo.org/record/7718512

I wonder if the navies have secret high resolution maps of the sea floor for submarine operations...

They do, but these maps are either incomplete, or they don't always follow them.

The Los Angeles-class nuclear submarine USS San Francisco (SSN-711) nearly sank on January 8, 2005, when it hit an uncharted undersea mountain about 364 nautical miles (675 km) southeast of Guam while operating at flank (maximum) speed at a depth of 525 feet (160 m). [1]

The Seawolf-class nuclear powered fast attack submarine USS Connecticut (SSN-22) suffered damage on October 2, 2021, after it collided with an undersea mountain while maneuvering in the South China Sea. [2]

And the Swiftsure-class nuclear powered fast attack submarine HMS Superb (S109) had to be decommissioned ahead of schedule due to the damage it suffered during a collision with an underwater pinnacle in the Red Sea, 80 miles (130 km) south of the Suez Canal. [3]

[1] https://en.wikipedia.org/wiki/USS_San_Francisco_(SSN-711)?us...

[2] https://en.wikipedia.org/wiki/USS_Connecticut_(SSN-22)?usesk...

[3] https://en.wikipedia.org/wiki/HMS_Superb_(S109)?useskin=vect...

Makes you wonder why they don't have forward-facing sonar as standard during non-secret ops. I mean, there's not a whole lot of shifty things you can be doing off Guam, if you already own the place.

The position of most submarines at any given point is considered actually secret, especially if it is underwater. Great expense is undertaken to monitor and listen for other countries undersea vehicles as well.

There's always training as a good excuse for running silent. Apart from that ... well, I'm not quite sure what these fast attack submarines are doing out and about at all. Maybe looking for other subs in the area? But whatever they are doing probably benefits from being hard to detect. If you are comfortable with announcing yourself with active sonar and are not just on the way to somewhere else, why not just use a surface ship in the first place?

What do you think would be easier: tracking a sub when you have tons of data linking your clandestine sensors' information to their location as broadcast by sonar, or when you don't?

former US submariner here:

* forward-facing sonar is always being used at all times while a submarine is underway

* however, the sonar that's always used is passive, and since mountains don't move, passive sonar doesn't find them

* active sonar could theoretically be used, but the risk of communicating a submarine's position relative to the chance that you'd hit an underwater mountain is balanced strongly on the side of running silent.

Thanks for sharing an informed perspective!

(Former US submariner)

Yes, and no.

Yes- the US has maps with higher-resolution data on water depth around the world than what's commercially available.

No - those maps aren't perfect. Some areas are extraordinarily well-mapped, others are less so.

Submarine crews are trained not to check just the charts that are in use for a particular voyage, but also other charts covering the same area. (The USS San Francisco collision has no evidence of a seamount on the charts in use, but there was "discoloration" on another chart covering the same area.)

Jonesy: "Sir, remember the dispatch we got about Russian sub skippers running the Canis ridge at high speed because they had hyper accurate surveys of the underwater canyons?

Capt Mancuso: "Yeah, yeah, red route 1"

- The Hunt for Red October

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