[teeman8r]

um, it’s a pile of rocks.

more likely ballast that sank with a ship.

[Openurmind]

“more likely ballast that sank with a ship.”

Bingo. I think so too. Sinking not even needed. If you had an empty ship load ballast would be needed to off set the lack of load. So if you took on more load from another ship such as an act of pirating the ballast would have to be dumped as you add more load. And because it would be impossible to stay static in one location it would leave a line of ballast on the bottom as it was dumped.

[Red Badger]

https://www.pnas.org/doi/full/10.1073/pnas.2312008121