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 ?

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    $\begingroup$ @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. $\endgroup$ – kaberett May 7 '14 at 15:31
  • $\begingroup$ @kaberett Biodiversity depends of the depth, you won't find the same species at -20m, than at -50m, than at -200m and so on... $\endgroup$ – Trevör May 7 '14 at 15:33
  • $\begingroup$ @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 :-) $\endgroup$ – kaberett May 7 '14 at 15:37
  • $\begingroup$ @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. $\endgroup$ – Trevör May 7 '14 at 15:42
  • $\begingroup$ Question is "How do I find seamounts within [insert-distance] below the surface near [insert-location]?" $\endgroup$ – blunders May 7 '14 at 15:44

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.

  • $\begingroup$ "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. $\endgroup$ – blunders May 7 '14 at 14:39
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    $\begingroup$ (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. $\endgroup$ – kaberett May 7 '14 at 14:42
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    $\begingroup$ ............ Woods Hole is the world leader in this field. They are the authoritative institution. I don't know what more you want. $\endgroup$ – kaberett May 7 '14 at 15:00
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    $\begingroup$ (+1) I didn't realise Mauna Kea was so tall! $\endgroup$ – Chris Mueller May 7 '14 at 15:12
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    $\begingroup$ 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... :-) $\endgroup$ – blunders May 7 '14 at 15:23

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.

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).

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    $\begingroup$ Just adding fuel to the fire... :P $\endgroup$ – Richard May 7 '14 at 16:55

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


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