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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 ?

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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, 2014 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... $\endgroup$ May 7, 2014 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, 2014 at 15:37
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    $\begingroup$ Question is "How do I find seamounts within [insert-distance] below the surface near [insert-location]?" $\endgroup$
    – blunders
    May 7, 2014 at 15:44
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    $\begingroup$ 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. $\endgroup$
    – blunders
    May 7, 2014 at 22:37

4 Answers 4

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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.

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    $\begingroup$ "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, 2014 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, 2014 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, 2014 at 15:00
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    $\begingroup$ (+1) I didn't realise Mauna Kea was so tall! $\endgroup$ May 7, 2014 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, 2014 at 15:23
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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).

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    $\begingroup$ Just adding fuel to the fire... :P $\endgroup$
    – Richard
    May 7, 2014 at 16:55
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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

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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

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