Geology of Iona
The geology of Iona is as special as the island itself and is very different from the volcanic Basalt rock covering most of Mull and even from the granite and schist dominated geology of the Ross of Mull only a few hundred metres away across the Sound of Iona.
Amongst the oldest rocks known on earth, Lewisian Gneiss outcrops on Iona and dates to 2700 million years old. It's red and black banding can be seen clearly on water worn rocks close to the beach at the north end of the island. Thought to be of a similar age the famous Iona Marble can be found on the southeast coast - it is a white marble with green and yellow veining.
Seen in on the low lying parts of the east coast of Iona are sheets of Torridonian Flagstone. Some 600 to 800 million years old this is a very hard, dark gray rock originally laid down as silt and sand in ancient deltas. Indeed, the ripple marks formed by the wash of water over the silt can still be seen today.
Also found on Iona in the south central region of the island, is an outcrop of white rock called Anorthosite. Perhaps almost as old as the Gneiss, Anorthosite is also found on the moon giving rise to its lighter coloured areas.
For more information about the fascinating geology of Iona and Mull visit the Mull and Iona Geology web site at www.mullgeology.com. From here you can navigate to maps, excursions, specific geological sites and many more data pages.
