The mysterious underwater pyramid at Yonaguni in Japan

[PlasmaSphere]

This has intrigued me, mainly because a lot of the scientists that go and see it for themselves change their mind and end up thinking that it is not a natural formation. It is an absolutely huge stone monument off the coast of Japan, and it has right angle sides, parrallel ledges, steps, and various other features that are hard to explain by nature.

the history channel did a documentary on it a while ago, an overview of it can be seen here; http://uk.youtube.com/watch?v=XMMBLNJqw1M#GU5U2spHI_4

http://www.morien-institute.org/yonaguni.html
"The structure was found by dive tour operator Kihachiro Aratake in 1985 and has been a source of controversy ever since. It appears to be a construction made of wide terraces, ramps and large steps. [...]

[...] According to the report, Japanese scientists have documented marks on the stones that indicate that they were hewn. Not only that, the tools used in this process have been found in the area, and carvings have been discovered. A small stairway carved into the rocks appears to render the theory that this is a natural formation implausible."

some good pictures of it can be seen here (http://members.toast.net/rjspina/Japan's%20Underwater%20Ruins.htm)

[hypatia]

http://www.physicsforums.com/showthread.php?t=80477&highlight=Yonaguni

This has already been brought up, I still find it very interesting, and beautiful.

[PlasmaSphere]

I would like to see if any other natural rock formations have rocks at such clear cut right angles as this monument has. Some of them seem very precise, and i find it hard to see how they would form to be that precise underwater, water usually makes everything smooth. I cant find any other formations like this one from a quick look around, submerged or not.

[Locry]

yup, i really wonder why they keep insisting it's natural... i'm no expert but it really really looks man-made.

[matthyaouw]

It looks about as man-made as columnar basalt does at any rate...

[ErkDemon]

I think it's difficult to have a conclusive opinion based on the documentary. People have historically shown a predeliction for building settlements on high rock structures and carving the outlying regions to suit, so it might be totally natural, or it might be artificial, or it might be a bit of both.

One thing that I would query in the documentary is their idea that if the rock is artificially shaped, that that stoneworking must date from the Ice Age, when global sea levels were lower.

Coastal cities sometimes sink over comparatively short periods of time, for instance, the archeologically-interesting bits of Alexandria are now under quite a lot of water.
en.wikipedia.org/wiki/Alexandria
Sometimes the sinkage is pretty sudden, e.g. Port Royal
en.wikipedia.org/wiki/Port_Royal
... we wouldn't date the underwater remains of Port Royal or Alexandria as going back to the last Ice Age, because we know that isn't true ... they sank due to local geological effects.

Given that the islands that make up Japan run along a faultline between tectonic plates (part of the "Ring of Fire"), and the region is notable for being geologically active (which is why the islands are there!), it seemed a bit odd for the documentary guys to be trying to date any potential human involvement based on mean global sea levels.

[Cyrus]

wow, thats interesting!

[Andre]

And then there is also Mega, the Cuban submerged megalithic site, discussed here (http://www.physicsforums.com/showthread.php?t=86402). It's still there but almost forgotten.