Atlantic Sea Mounts

[Charlie]

How do you locate the Atlantic seamounts. It seems to me it would be valuable to know where they are so that if you get caught in a storm you would be able to avoid them because of breaking waves etc.

[dpons]

Charts?

[Healer52]

If you're caught in them, it's kind of too late.

[Charlie]

Originally Posted by dpons

Charts?

Do they have charts that have enough detail for each section of the ocean. I guess they do but I don't know that I could afford them all

Originally Posted by Healer52

If you're caught in them, it's kind of too late.

The idea would be to avoid them. Hard to do that if you don't know where they are.

[flysci]

Try:

Atlantic Seamounts

Has some Lat/Long info.

Margo

[daddle]

The small scale (1:3,500,000 for example) planning charts a designed to show everything shoal, no matter how small, with at least a dot of ink. At least that's what I understood from somewhere. So no need for the large scale charts in many cases.

[s/v Beth]

Do we have a geologist around here to tell us how often things change? I hear the big earthquake in Sumatra changed some of the depth for seamounts...

[Astrid]

The main danger sea mounts is not the ones you know are there, since you can avoid them, but the ones that have never been charted.

[RainDog]

NIMA Nautical Chart Folio W12 - Atlantic Ocean Passage Maker: Brittish Isles & Mediterranean Sea to Caribbean Sea & Gulf of Mexico - 18 Charts | Bellingham Chart Printers

[conachair]

Originally Posted by Charlie

How do you locate the Atlantic seamounts. It seems to me it would be valuable to know where they are so that if you get caught in a storm you would be able to avoid them because of breaking waves etc.

I've just pulled out imray north atlantic passage chart and basically there aren't many. The biggest ones are above the water - Azores, bermuda and canarys A few SSW of Azores, they seem all to be on the chart and have names. The rest looks like over 4000m of water under the keel. But the logic is probably sound, I would avoid them even in calm weather.

[Astrid]

Do we have a geologist around here to tell us how often things change? I hear the big earthquake in Sumatra changed some of the depth for seamounts...

Usually with a sea mount, if an major earthquake strikes near one, the most usual change in depth would be caused by the collapse of one side or slope to the mount and this could cause a reduction in the height of the sea mount. It would also tend to spawn a tsunami.

Most sea mounts are in relatively deep water and it is unlikely that a yacht would actually run onto one, though not entirely impossible. There have been several vessels damaged by striking a shallow, uncharted sea mount, including the USS San Francisco (2005) and the SS Muirfield (1973).

There are an estimated 100,000 sea mounts, and only a fraction of them have been charted--about 13,000. Being volcanoes for the most part, sea mounts can grow, eventually some of them becoming proper islands.

[elhix]

Check this out:

www.tos.org/oceanography/issues/issue_archive/issue_pdfs/23_1/23-1_sandwell.pdf

"more than 50% of the seafloor lies more than 9.5 km from the nearest ship sounding"

[dpons]

Originally Posted by Charlie

Do they have charts that have enough detail for each section of the ocean. I guess they do but I don't know that I could afford them all

The idea would be to avoid them. Hard to do that if you don't know where they are.

Sailing is a very fulfilling activity with some risks. If you don't use charts, you increase the risk. Yet even if you use them, you can't eliminate all risks.

Even if you had a map with all the idiots in your town, you'll be taking some risks crossing a street.

The pic is of a very small island in the middle of the Atlantic, Peter and Paul Rocks. Note the absence of mega waves.

[hpeer]

Google Earth might be another way to get a start. It would let you find the significant features in your area of interest pretty quickly.

[estarzinger]

Originally Posted by Charlie

How do you locate the Atlantic seamounts.

The 'normal tool' is a small scale (eg whole ocean) B&W chart - does not cost much and shows the sea mount detail you need.

The most 'dangerous' Atlantic seamount is in the South Atlantic, right on the direct route beteen CApe Town and St. Helena. It's worth detoyring around - comes to within about 20m of the surface if I remember correctly (on the 'walvis ridge')

There is a neat tool at http://seamounts.sdsc.edu/ where you can locate seamounts by ocean and depth.