Geograph - photograph every grid square

The metasedimentary rocks of northern Iona are possibly the most recent rocks on the island, though beyond "Late Proterozoic", geologists are not prepared to commit themselves. Exactly which formation is forming this rock pool is unclear as the Ross of Mull Geological Map (Scotland sheet 43S) shows only the drift (Blown Sand) at this location but extrapolating from nearby outcrops shown on the map, interbedded fine-grained metasandstone and metasiltstone of the Iona Group (possibly somewhat hornsfelsed) seems likely. Across the Sound, one is in an entirely different terrane (the Moinian rather than the Hebridean) with the Moine Thrust itself being concealed under the water. The Ross of Mull, seen on the right, is a 440 million year old granite intruded into the Moine series, whilst the Ardmeanach peninsula seen in the distance is composed of layers of basalt in lava flows from the much more recent geological past, being part of the Tertiary Volcanic region.