When surveying penguin colonies on subantarctic Antipodes Island, we found a cave that features a strange rock formation: Rock cairn or natural formation?

The formation does not appear to be particularly exposed to the elements so that abrasive forces may not be at work here. The cave is located in a large bay in the northwest of the island that is only accessible from the sea. Today the bay hosts a large colony of fur seals that were nearly hunted to extinction by sealers in the early 1800s. The cave would be a perfect spot for the sealers to camp out and stash the skins, so it is plausible that it served as a base for sealing operations. Hence, the possibility that the formation is indeed man made.

However, the rocks it consists of look rather large and potentially heavy which would speak for a natural rock formation.

Probably relevant to mention that Antipodes Island is of volcanic origin.

Any opinions of folks with knowledge in Geology would be greatly appreciated!

Here is a 4K video of the "cairn" filmed with a drone: https://www.youtube.com/watch?v=j9imJUytp6Y

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    $\begingroup$ It was probably the penguins! $\endgroup$ Commented Feb 15 at 5:04
  • $\begingroup$ Let's just say...that's not sand on the floor of the cave. $\endgroup$
    – Spencer
    Commented Mar 26 at 21:59

1 Answer 1


The fur collection on Antipodes Island lasted for about seven years or so, from 1800 to 1807. This is an extremely isolated island that lies at the boundary between the roaring forties and furious fifties.

How could a small, ragtag group of sailors have brought the heavy machinery to that extremely remote island needed to carve that cave in a mere seven years? OTOH, the island is volcanic, is chock full of caves, and is subject to some of the most severe storms on the planet. It's almost certainly a natural formation.

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    $\begingroup$ The question is about the origin of the cairn-like feature at the center of the photo, not about the origin of the cave itself. $\endgroup$ Commented Feb 14 at 10:39

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