Thu 12 Apr, 2018 11:23 am
I have a photo of Surtsey Island showing a large pile of very smooth large stones. Since this island is quite young, how could these rocks and stones have got so smooth and rounded?
Pillow Lava maybe? Can you send a link to the photo's?
Yeh, volcanic concretions or pillow basalts are good candidates. If its from the recent ruptions itd be just a few decades old.
Heres a picture of septerian (Moeraki) concretions from New Zealand.These are about 60 my old