On our first dive at Yonaguni I took Wolf to a very curious structure that I had discovered in late June 1999.
It stands in 18 metres of water 100 metres to the west of the terraces of the main monument. When above sea level 8000 or 10,000 years ago I suggest that it was originally a natural and untouched rocky knoll rising about 6 metres above ground level. A curving sloped ramp 3 metres wide was then cut into the side of the knoll and a retaining wall to the full height of the original mound was left in place enclosing and protecting the outside edge of the ramp.
I lead Wolf to the base of the ramp and as we swam up it I pointed out how the outer curve of the inner wall -- which rises two metres above the floor of the ramp and is formed by the body of the mound - is precisely matched by the inner curve of the outer wall, which also rises to a height of two metres above the ramp floor, so that both walls run perfectly parallel. Moreover when we swam up and over the rim of the outer wall we could see that its own outer curve again exactly matches the curves within and that it drops sheer to the sea-bed - as it should if it is indeed a purposeful wall and not simply a natural structure.
I showed Wolf that the ramp floor itself, though battered and damaged in places, must originally have had a smooth, flat surface. I also showed him what I believe may have been the function of the ramp. As one continues to follow it round it leads to a platform offering an impressive side-on view of the two huge parallel megaliths, tucked into an alcove in the northwest corner of the main monument, that constitute a spectacular landmark in the Yonaguni “underworld”.
Later we discussed what we’d seen:
GH: Okay, Wolf, the first dive we did I brought you to a structure [attempts to draw ramp structure on notepad] - I'm sorry, I'm hopeless at drawing..
WOLF: Me too [peers at drawing] OK, so I recognise it.
GH: Hey, you're a geologist, you should be able to draw. [Continues drawing] And here is a rather nice wall going round on both sides, and in the middle is a bedrock channel or ramp. And it rises from here around to this corner and, in fact, if we follow it all the way round it leads us to a view of the megaliths. Now this wall is not a bank. It is a wall. It's actually about half a metre wide wide. And it's high more than 2 metres high
WOLF Round about.
GH: Above this above this ramp, whatever you want to call it. So I simply cannot understand the combination of clean bedrock here [indicates the ramp floor], admittedly very eroded and damaged - but clean bedrock here, and these heavily overgrown walls, which are definitely wall-like in appearance and rather high in the sense that they have an outer and an inner edge, and the curve of the outer edge matches the curve of the inner edge; and the same on the other wall.
To my surprise Wolf immediately admitted that this rather innocuous looking and only recently discovered structure, which he had not been shown on his previous visit, was a “real challenge”. He was later to describe it as “the most impressive thing” he had seen at Yonguni:
“The most impressive thing for me was the wall, the wall which is totally covered by living organisms nowadays, which should be removed to have a look at the structure of that wall, which can also be explained as having been done possibly by nature, but to get it sure we have to do deep research on that.(14)
Nevertheless Wolf would not have been Wolf if he had not at least attempted to comeup with a calm, level-headed and unsensational geological explanation for the problem. He therefore drew my attention now to a place on land on Yonaguni called Sananudai that we had taken a look at the day before where he had shown me wall-like formations - admittedly only half a metre high - that had been formed entirely naturally:
WOLF: Okay, this is a real challenge to solve. But if you remember, the day before we have been on a platform on land - I forgot the name of the point -
WOLF: Right, correct. And by chance we went further down near the sea, and I showed you these encrustation patterns and maybe you remember that I..
GH: I remember distinctly; you told me that a hard patina formed on the outside of the rock and that the water softened out the inside, leaving a wall -like shape in place.
WOLF: Correct. And on the other side, the relatively soft sandstone had already begun to be removed. So And I told you that this could be a possible way that a wall can be made by nature OK, it’s a theory.
GH: It's a theory. I mean what I saw at Sananudai was actually no curved walls running in parallel with each other, but rather straight and they were about half metre high.
WOLF: They were at beginning stage. Right. And if you had a look closer down, you would have seen that there was a little curving, not as clear as this, I have to admit. But I mean that was really the beginning stage so we don't know.
GH: So would you want to explain those walls [on either side of the ramp] that way, as a hard patina which was preserved, and the soft part was cut out?
WOLF: At first, and then subsequently overgrown by organisms as we saw. But to get clear what that really is, so I underline repeatedly, it is a challenge, and this is the first and only explanation I have for this. But to really get clear of this fact, we should have to remove the encrustation on one spot, or just from top to the bottomThis is the only way to find out of what material this wall consists - there's no other way; or to drill a hole through We are obliged to find out what these walls are made of. Are they made of single patterns like stones or something?
GH: Well see, I don't I very much doubt if the walls will turn out to be made of blocks. I think they'll turn out to be cut. I think we're looking at a megalithic culture which cut rock. I think they cut down into the living rock, and they created the walls by cutting, and then later on the encrustation came and grew on top of the walls. That's my theory.
WOLF: I mean, if this was the case, then it would still be very useful to have a look on the core of these. It would tell us exactly what sort of material it was - was it soft sandstone, was it hard mudstone or what else? And we would be possibly able to find any marks on them, which then would give us the clear proof
GH: So what we have here is a bit of a puzzle which needs some serious research done on it.
WOLF: Correct. That's what I would say.