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Per Oxford Dictionary of Earth Sciences: Seamounts are 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.

Per kaberett: 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.

Per Wikipedia: A seamount is a mountain rising from the ocean seafloor that does not reach to the water's surface (sea level), and thus is not an island.

Per Oxford Dictionary: Submarine means "Existing, occurring, done, or used under the surface of the sea."

Per NOAA: A seamount is an underwater mountain on the seafloor.

Are all seamounts below the water, or do they include formations that rise above the water?

UPDATE: Atolls not within the scope of defining formations that rise above the water; meaning atolls are atolls, and not seamount crests.

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blunders
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    Yes, they are all under the surface, as your research shows. Why this question? – milancurcic May 07 '14 at 16:14
  • @IRO-bot: kaberett does not agree with you and me, and the source of the question is a bad question and might be deleted. – blunders May 07 '14 at 16:16
  • @IRO-bot Some sources mention that seamounts can break the ocean's surface. Also, it's not as cut-and-dry as "if it's above the surface, it not a seamount", since tides impact this. – Richard May 07 '14 at 16:21
  • @Richard: As noted in my comments to kaberett, I called Woods Hole. At first, they were unable to provide a source, then said the source was "on a boat"... :-) ...so, I personally do not mark them as a source, though maybe I'm being too hard on them; emailed the content lead, so they could ping the guy on the boat, who would "speak to scientist" - if I get a reply, I'll provide an update. – blunders May 07 '14 at 16:26
  • @Richard Sure, but does that really matter? You could say that about many small islands. Those are special cases. Seamounts in general are determined and labeled as such in an arbitrary manner so there is no space to be exact and nit-picky about it. – milancurcic May 07 '14 at 16:26
  • @blunders I see. I did not follow that long comment chain. – milancurcic May 07 '14 at 16:29
  • @IRO-bot It sounds like you have an answer, then. You should post it. – Richard May 07 '14 at 16:34
  • @Richard OK, let's see if we get a good answer before weekend. I will consider it then. Too busy right now to write a good answer. – milancurcic May 07 '14 at 16:37
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    just for clarity, we're not including seamounts which may have subsided and are now below the sea surface but have formed atolls which break the surface? – Siv May 07 '14 at 16:48
  • +1 @Siv: Right, coral, sand, etc. is not the seamount. – blunders May 07 '14 at 16:51
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    You ask "What is a seamount" but already give a number of alternate answers yourself. Answers can merely give yet more definitions. I think this question appears to solicit debate, therefore I am closing. Feel free to edit the question to address my concerns. – gerrit May 07 '14 at 17:28
  • @gerrit: So, you're saying terminology questions are off-topic? – blunders May 07 '14 at 17:30
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    @blunders No, it's not off-topic. It's unclear. I'm saying your question is unclear because you already give five alternate answers yourself, some more authoritative than others. What would make you accept yet another definition when these five do not answer your question? – gerrit May 07 '14 at 17:34
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    @gerrit: First, I let me say the question appears to be a non-trivial question and of value. My take, though open to the communities view, is what matters is data, since authoritative opinions on the topic are at best subjective. As such, my position is the definition used by the largest (utilized) database of seamounts would be the best source understanding what seamounts are, and are not. – blunders May 07 '14 at 17:48
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    @blunders Ok, then ask what definition is used by the largest utilised databases of seamounts? – gerrit May 07 '14 at 18:36
  • +1 @gerrit: Okay, posted that question as a new question, since as I stated, that's my opinion, and as it relates to this question, I am open to what the comminuity view is on the correct answer; so far, based on the lack of votes on the answers, appears the answer is there is no answer. – blunders May 07 '14 at 18:44
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    @gerrit Just because there isn't a single straightforward answer doesn't make it a bad question. – 200_success May 08 '14 at 17:25
  • @200_success It's not a bad question for not having a single straightforward answer. It's an unclear question because it doesn't show what additional information is requested, beyond information already given in the question. – gerrit May 08 '14 at 20:19
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    @gerrit I think the OP just wants to sort out the confusion, that's all. The confusion is addressable, and therefore the question doesn't deserve to be closed. – 200_success May 08 '14 at 20:22

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A seamount is, quite simply:

an underwater mountain rising above the ocean floor
Source

The term, however, does not have scientific consensus.

Some definitions include only formations over 1km in height, while some include formations as short as 100m. Some definitions say that the formation must be exclusively underwater, while other definitions include the the rise of the formation above the sea floor, even to the point of forming an island. Some definitions even include islands within the definition of seamount.

In the end, a "seamount" has to be defined within each study that uses it, since there is no consensus on whether to include super-surface formations.

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Richard
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Staudigel et al. (2010):

The term seamount has been defined many times (e.g., Menard, 1964; Wessel, 2001; Schmidt and Schmincke, 2000; Pitcher et al., 2007; International Hydrographic Organization, 2008; Wessel et al., 2010) but there is no “generally accepted” definition. Instead, most definitions serve the particular needs of a discipline or a specific paper. [...] As we explore the major differences among definitions of the term “seamount,” several important issues play a role:

  • The inclusion of the temporarily emergent portions of seamounts is relatively obvious for geologists who look at seamount construction over long time scales. Many large seamounts either have summit regions that currently breach sea level, or at some point they emerged and are now entirely submerged. Hence, temporary emergence is part of the life cycle of many very large seamounts. The inclusion of emerged summits, however, is counter intuitive for a biologist. Biological communities on land are dramatically different from submerged communities and, hence, data from the emerged fractions of a seamount cannot be reasonably included into a focused marine biological study. The complexity of this issue is illustrated by Lō'ihi Seamount (see Spotlight 3 on page 72 of this issue [Staudigel et al., 2010]), an entirely submerged seamount that is located on the submarine flank of Mauna Loa, the largest volcano of the Hawaiian Islands.

[...]

  • Some seamount definitions also include aspects of their shape, in particular, restricting their use to conical features, whereby flat-topped (“tablemount”) seamounts are commonly called guyots. This morphological distinction is significant insofar as flat-topped seamounts are likely to once have been islands or coral reefs, while conical ones are likely to not to have breached the sea surface during their life cycle (Staudigel and Clague, 2010).
  • In their original definition, seamounts were defined based on their tectonic setting, specifically, as features on the seafloor that are not part of mid-ocean ridges or subduction zones (Menard, 1964). This limitation to intraplate volcanoes pays tribute to the distinct magmatic processes that form volcanoes at mid-ocean ridges, arc volcanoes, and in intraplate settings. Apparent exceptions are mantle hotspots located at or close to mid-ocean ridges, such as the one presumed to exist under Axial Seamount at the Juan de Fuca Ridge (see Spotlight 1 on page 38 of this issue [Chadwick et al., 2010]) that appears to be the origin of the Cobb seamount chain. Wessel et al. (2010) restrict their use of the term seamount to intraplate features, excluding arc volcanoes in their seamount count.

Full citation: Staudigel, H., A.A.P. Koppers, J.W. Lavelle, T.J. Pitcher, and T.M. Shank. 2010. Box 1: Defining the word "seamount". Oceanography 23(1):20–21, http://dx.doi.org/10.5670/oceanog.2010.85.

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