Ardnamurchan; May 6 – May 9 2022

Leader: Con Gillen

Field days: Friday (afternoon)/ Saturday/ Sunday/ Monday (morning)

This trip was originally planned to take place in 2020, but was cancelled because of Covid-19. Priority will be given to those members who had expressed interest in the original excursion.

The Ardnamurchan peninsula, which includes the most westerly point of the Scottish mainland, is composed mainly of the remains of an early Palaeogene volcano with three centres of activity. Part of the North Atlantic Igneous Province which includes Mull, Rum and Skye, it was erupted into Moine metasedimentary rocks and overlain by a sequence of thin sedimentary rocks. Ardnamurchan displays classic geology on a colossal scale, with features such as mixed magma, ash flows, ring dykes, cone sheets and examples of “airfall” rocks formed from lava ejected from the heart of the volcano – it is regarded as almost a “textbook volcano”. A drive across the peninsula is a journey through its magma chamber. Its overall structure is difficult to perceive on the ground but from space the picture is much clearer – rings of once molten magma can be seen to define a series of almost perfect circles. These are the lower parts of the volcano after the superstructure has been planed off by erosion, in this case, effectively, by the last Ice Age. We plan to visit significant localities of igneous, sedimentary and metamorphic rocks and there may also be the opportunity to sail to Tobermory (whales!) for those who wish to do less climbing!

Accommodation will be B & B in Kilchoan etc.; transport will be in shared cars.

This excursion is now fully booked.

Snowdonia; September 9 – September 12 2022

Leader: Simon Cuthbert

Field days: Friday (afternoon)/ Saturday/ Sunday/ Monday (morning)

The landscape of Snowdonia National Park, “Parc Cenedlaethol Eryri” in Welsh (Eryri means place of the eagles) is dramatic and varied, with mountains, high passes, craggy peaks and precipices and cascading waterfalls. The elegant pyramid of Snowdon – Yr Wyddfa – is the highest peak at 3,560ft. Snowdonia’s geology consists of sedimentary, volcanic and intrusive rocks of late Proterozoic to Silurian age. The rugged mountain scenery is dominated by the Ordovician volcanics, including spectacular pyroclastic rocks, all related to subduction of the Iapetus Ocean crust. The geochemistry of the igneous rocks suggest that they formed as part of the back arc basin in a volcanic arc system. These, and the famous Cambrian slates that “roofed the world” were intensely faulted, folded and subjected to low-grade metamorphism during the Caledonian Orogeny. The region was uplifted as the North Atlantic opened during the Cenozoic while the current mountainous landscape and its cwms (corries) have resulted from repeated late Cenozoic glaciations, as recognised by Charles Darwin during his travels in the area.

The trip will focus on the Ordovician volcanics in which we can see evidence for giant ash-flow eruptions in the extensive ignimbrites. We will also examine the large-scale Caledonian folding, all set in Eryri’s wonderful glacier-carved mountain scenery. We may also manage a trip on the Snowdonia mountain railway!

Accommodation will be B&B; transport to be decided. If you are interested, please contact the Residential Excursions Secretary, Maggie Donnelly at restrips@gsocg.org.