ALT Investigating evidence for glaciation. Members of an International Subcommission on the Cryogenian System investigate evidence for glaciation on Eileach an Naoimh (holy isle), one of the Garvellach islands in Scotland

ALT An outcrop called ‘the Bubble’ on Eileach an Naoimh (Holy Isle). It shows a huge white rock fragment, tens of metres across, which was originally part of the underlying rock sequence. The layering in the carbonate rock has been squeezed tightly under immense pressure and transported by thick ice sheets to its final resting as one of many different rock fragments within a moraine

ALT Tony Spencer, co-author of the latest study and of a classic 1971 memoir about the rocks, standing in 2023 on glacial till of the Port Askaig Formation on Garbh Eileach, the largest of the Garvellach islands

ALT A view of Garbh Eileach, the largest island in the Garvellach island chain where the gradational transition into snowball Earth is recorded