Mysterious island in Argentina

[Pollux]

I wonder if it could possibly be so that; beneath the floating circle/island there is some sort of sinkhole. A sinkhole that is smaller than the "island" there, and that the sinkhole possibly is connected to some underground stream, with cooler water. Imagine the sinkhole to be half the diameter, or maybe less, than the rotating island, and that it always have streaming/cooler water passing by that hole, and that the grass that has grown in that delta, on that spot, has never been able to come to a still - and creating that "rug" of grass-growth - we see on the rest of the delta.

If there always is spinning water, and cooler water meeting warmer water, all the time at that spot, I can imagine this patch of grass forming a larger circular patch over the sinkhole, and that it is always in constant motion, creating that "island",  by grinding its edges against the permanent grass-growth around it.

I would have thought a circular shape would be an almost inevitable shape, as opposed to say triangular or square. I can see non-circular shapes being an outcome if all the forces (wind or water current) are consistently in a limited range of directions (e.g. back and forth motion in a tidal estuary).

Well, maybe it could be natural. Here's another floating island in Italy, which has been there since classical times:
https://it.wikipedia.org/wiki/Lago_di_Po...lleggiante

Well, maybe it could be natural. Here's another floating island in Italy, which has been there since classical times:
https://it.wikipedia.org/wiki/Lago_di_Po...lleggiante

Here's Google's satellite view of the Italian example:

[Image: LaRota.jpg]

I wonder if it could possibly be so that; beneath the floating circle/island there is some sort of sinkhole. A sinkhole that is smaller than the "island" there, and that the sinkhole possibly is connected to some underground stream, with cooler water. Imagine the sinkhole to be half the diameter, or maybe less, than the rotating island, and that it always have streaming/cooler water passing by that hole, and that the grass that has grown in that delta, on that spot, has never been able to come to a still - and creating that "rug" of grass-growth - we see on the rest of the delta.

If there always is spinning water, and cooler water meeting warmer water, all the time at that spot, I can imagine this patch of grass forming a larger circular patch over the sinkhole, and that it is always in constant motion, creating that "island",  by grinding its edges against the permanent grass-growth around it.

Your explanation seems to be supported by the Italian Wikipedia article, which implicates underground currents in the formation and movement of the Italian example. This is an English version from Google Translate:

"Almost certainly, the floating island was originated by an exceptional underground current that caused the peat bottom to rise from almost nine meters below the water level.

The island, locally called "La Rota" due to its roundish and conical shape (with a downward tip) of about thirty meters in diameter, moves and turns like a spirograph inside its flooded doline*, thanks to light breaths of wind or for the increase of the flow of the sources that flow near the area of relevance."

(* Doline is another name for a sinkhole!)

The El Zacaton sinkhole in Mexico has a number of floating islands, though the largest is only perhaps 20% as big as the sinkhole itself:
https://www.mnn.com/earth-matters/wilder...el-zacat-n

[Pollux]

Your explanation seems to be supported by the Italian Wikipedia article, which implicates underground currents in the formation and movement of the Italian example. This is an English version from Google Translate:

"Almost certainly, the floating island was originated by an exceptional underground current that caused the peat bottom to rise from almost nine meters below the water level.

The island, locally called "La Rota" due to its roundish and conical shape (with a downward tip) of about thirty meters in diameter, moves and turns like a spirograph inside its flooded doline*, thanks to light breaths of wind or for the increase of the flow of the sources that flow near the area of relevance."

(* Doline is another name for a sinkhole!)

Yeah, the conical shape would make sense if it is a constant spin over a hole.

The island here in Argentina, they say, has been there since some 20 years. The delta has been there far longer though, so I think it is possible that a sinkhole has naturally emerged beneath that patch, and when the water started to stream there, causing a slow whirlpool, it ripped lose the grass from the "rug" and slowly created that circle. It's plausible.

Sinkhole in general are on the top of things I never ever wanna experience close up. Since that guy in Florida, whose bedroom was swallowed up, when he was sleeping there, sucked him down some 30 feet in a mud-sinkhole to be buried alive, this are on my top list of; horrific-ways-to-go.

Imagine waking up in the middle of the dark night, feeling that the floor gives way, and you are sucked down in a hellhole, and it closes around you!?!





The guys who caught this incredible footage are either reckless or incredibly brave. I mean, there is no telling how large this sinkhole might be, and when it swallows up some 65 foot trees in a matter of seconds there is no telling how deep and wide this hole might expand to. Standing that close to the center is rather reckless. They could be sucked in in a matter of seconds if the hole gets big enough.

Just look how these trees are swallowed up - in seconds.



When we know that sinkholes can get as large - as in this picture below - standing around when one emerge is quite reckless.

This sinkhole in Guatemala, that swallowed up a whole intersection, and some houses, was  65 ft (20 m) across and 300 ft (90 m) deep





The worst one though, was the collapsing salt mine in Lake Peigneur, in the 1980's - caught on film
Almost surreal. The whole lake disappeared - sucking down 11 large barges and a tug-boat, like they were toys, in an enormous, gigantic, whirlpool.




I'm glad I live in a country were sinkholes aren't common.
We stand on a bedrock (Scandes), made of mostly granite.

Well, maybe it could be natural. Here's another floating island in Italy, which has been there since classical times:
https://it.wikipedia.org/wiki/Lago_di_Po...lleggiante

Not since classical times - evidently the quotations in Wikipedia referred to a floating island in a different lake, which has not survived. 

Scientific analysis of the Posta Fibreno island indicates an age of 700 years:
https://www.nature.com/articles/srep43040

Interesting article:

https://www.gearthblog.com/blog/archives...ntina.html

[Pollux]

Interesting article:

https://www.gearthblog.com/blog/archives...ntina.html

Have a look;



http://www.skeptiko-forum.com/threads/uf...ost-117640

and; http://www.skeptiko-forum.com/threads/uf...ost-117676

Here's a video that is (theoretically) showing other such lakes. Maybe it's not as much of a one-off as thought.