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I am wondering what is the tallest fully underwater seamount in the world ? When I say the tallest, I mean the one that is the nearest of the sea level. EDIT : The highest that I found would be at about 50m below the water's surface do you know any other seamount that would be even higher ?

Pop Flamingo
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    @TrevörAnneDenise I'm afraid I don't understand the motivation for knowing which seamount currently most closely approaches the surface without breaking it. This tells you nothing about processes - it's completely dependent on which sea level you pick. Mounts in the Hawai'ian-Emperor chain have been gradually eroded backwards; Surtsey only became a permanent island in 1964. Sea level isn't a constant. I don't understand why this question is meaningful, as it stands. – kaberett May 07 '14 at 15:31
  • @kaberett Biodiversity depends of the depth, you won't find the same species at -20m, than at -50m, than at -200m and so on... – Pop Flamingo May 07 '14 at 15:33
  • @TrevörAnneDenise Indeed not, but as seamounts are isolated the ability of benthic fauna/flora to reach them is questionable, cf morphological and genetic diversity between separated habitats (the example that springs to mind is trilobites in Scotland + Canada, and the obvious effects of continental rifting). If your question is about biodiversity, (1) can you edit that in, (2) clarify why it doesn't apply to Hawai'i (which covers the whole range of depths...?), and (3) clarify why you are interested in seamounts particulary as an environment? I'd be interested in seeing that explored :-) – kaberett May 07 '14 at 15:37
  • @kaberett Since I am french and not very good at english, I don't know if I understand very precisely what you are telling me but I'll try to answer to your questions. I saw and read many things stating that the seamounts have got a lot of animals on it. I am interested by seamounts because I might soon create a (reduced size) bot+submarine to explore a seamount that is pretty close to the island where I live. I was just surprised to see that it is only -50m below the surface and so I was curious to know if there was any other seamount that would be even closer to the surface. – Pop Flamingo May 07 '14 at 15:42
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    Question is "How do I find seamounts within [insert-distance] below the surface near [insert-location]?" – blunders May 07 '14 at 15:44
  • Seamount Catalog might be of use, though it does not appear to allow a direct query of distance below the surface. – blunders May 07 '14 at 17:25
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    So, did ask more questions, as you might have seen, and a database of 30000 seaamounts was linked to; the reasearcher claim it covers 94% of the seamounts. While so far it doesn't appear to cover the depth below sea-level, like the best starting point so far for your question. – blunders May 07 '14 at 22:37
  • That will be Mt. Pico, Azores, Portugal. –  Mar 10 '16 at 00:01
  • @Jim But it isn't a seamount ? – Pop Flamingo Mar 11 '16 at 05:13

4 Answers4

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According to the Oxford Dictionary of Earth Sciences,

seamount Isolated, submarine mountain rising more than 1000m above the ocean floor. The sharp, crested summits of seamounts are usually 1000-2000m below the ocean surface. Seamounts are of volcanic origin.

To avoid classifying seamounts by arbitrary sea level (dependent on availability of surface water), the key point is then that seamounts are features of volcanic origin that rise over 1000m above oceanic crust.

The Hawai'i-Emperor seamount chain is of volcanic origin; all of the islands in this chain are seamounts. Mauna Kea only rises 4207m above sea level - but measured from its base on the oceanic plate it is 10100m high, much taller than Mt Everest. Mauna Kea is - pretty conclusively - the highest seamount in the world. The Woods Hole Oceanographic Institute agrees.

kaberett
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    "A seamount is a mountain rising from the ocean seafloor that does not reach to the water's surface" - Mauna Kea is above sea level. – blunders May 07 '14 at 14:39
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    (1) That's not the definition that the ODES uses, as quoted; (2) if you use the (unsourced) Wikipedia definition the answer is trivially constrained by water depth. – kaberett May 07 '14 at 14:42
  • Hello, thank you for your answer but I don't think that these are the highest ones. For example, in the Indian Ocean at 180 km from the island where I live (Île de la Réunion) there is a seamount called "La Perouse Seamount" that would be at around -50m below the water's surface. – Pop Flamingo May 07 '14 at 14:44
  • I agree that the definition doesn't give the highest seamounts, rather the typical ones. I quoted the definition to clarify my interpretation of the question. – kaberett May 07 '14 at 14:46
  • Reread your ODES' definition, it clearly states seamounts are "submarine mountains" - right? – blunders May 07 '14 at 14:52
  • @blunders http://www.whoi.edu/main/topic/seamounts <-- Wood Hole disagrees. "Submarine" covers a multitude of sins, including "at least in part". Note that if they are defined as submarine then what meets the definition of "seamount" is entirely subject to present sea level, which does not to me seem a very helpful definition. – kaberett May 07 '14 at 14:53
  • Wow, "forget semantics, I'll just dig up a link" - submarine most clearly means beneath the water, and Wood Hole is confused; likely confusing that when a seamount surfaces, it's know as an oceanic island, and it's common for a seamount to become an oceanic island, then revert to being a seamount. – blunders May 07 '14 at 14:59
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    ............ Woods Hole is the world leader in this field. They are the authoritative institution. I don't know what more you want. – kaberett May 07 '14 at 15:00
  • @kaberett: ODES does not define submarine, but Oxford Dictionary define submarine as: "Existing, occurring, done, or used under the surface of the sea." - stand by my statements. – blunders May 07 '14 at 15:06
  • The important point about seamounts cannot be that they are in whole submarine, though - because the definition is then entirely subject to arbitrary sea level. The key point from that definition, from my perspective - and clearly from WHOI's - is that a seamount is a feature of volcanic origin rising over 1000m from oceanic crust. – kaberett May 07 '14 at 15:08
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    (+1) I didn't realise Mauna Kea was so tall! – Chris Mueller May 07 '14 at 15:12
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    Called WHOI and they said, the person that wrote that is at sea, so much for being able to nail down a source. So, guess I see no reason why you couldn't list the tallest fully underwater seamount too, which would resolve the issue until WHOI's able to ping the guy on the boat... :-) – blunders May 07 '14 at 15:23
  • FYI, the poster of the question means "nearest to the sea level" not tallest. – blunders May 07 '14 at 15:31
  • FYI, the image caption on the Wood Hole page states "A seamount, or underwater mountain, on the Artic Ocean seafloor. (NOAA)" – blunders May 07 '14 at 16:34
  • The WHOI page contradicts itself -- it says "underwater mountain", and then says it can break the surface (and gives Hawaii as an example). If a mountain's peak is permanently in the air, it's an island. If it's awash, it's a shoal. If it's permanently under water (barring major sea level changes), it's a seamount or guyout (flat topped, formerly at the surface but has subsided). – Phil Perry May 07 '14 at 17:04
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This answers one of the questions you list, but the shallowest seamount, per this list on Wikipedia is Banua Wahu, which is 8 meters below the surface, but has risen above the surface and fallen below the surface several times in recorded history.

However, this is definitely not the tallest seamount, standing only 400m high from its base.

Edit
A larger database by Yesson, C et al. includes several seamounts that are within 2 meters of the surface. However, the data does not suggest when the measurements were taken (high tide or low tide), which would have obvious implications. Also, there are many seamounts within that range (I stopped counting at 100).

Richard
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I was wandering around some seabed topos yesterday and found a spire at the bottom of the trench that rises from 35,000ft to 8,700, making this discrete and very steep spire about 26,000 feet high. enter image description here

Dad
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Re: Seamounts vs land based Mountains

Mt Everest is the highest land based mountain at 8,800m above sea level.

Mauna Kea seems the highest Seamount at 10,100m with 4,200m above sea level and therefore about 6,000m below sea level.

A typical Seamount is 1,000 to 4,000m which seems similar to land based mtns.

Somewhat avoiding debate over whether above of below sea-level Mauna Kea still seems the highest Seamount.

Another item of interest is what is the deepest ocean trench and it seems to be the Mariana Trench at -10,994m below sea level.

The Mariana Trench or Marianas Trench is located in the western Pacific Ocean about 200 kilometres (124 mi) east of the Mariana Islands, and has the deepest natural trench in the world. Elevation: -10,994 m.

Greg W

Greg W
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