After a 14-month hiatus, due to the global pandemic, GeoWorld Travel finally got back on the road again, with a small group, socially distanced tour of the geology of Scotland. For geologists the world over, Scotland offers a wealth of outstanding geological sites and has been host to a number of crucial events in the history of geology.
Arrival
Due to ongoing restrictions, we welcomed just five UK-based guests for our first tour of 2021. Our participants came from the Lake District, Leeds, Warwickshire and Oxfordshire. We all arrived in Edinburgh to stay the first night at a hotel near the airport – no welcome meeting this year, due to restrictions on indoor gatherings, but we had all met already and discussed the trip on a Zoom call two weeks before!
Day one
Our Scotland tour always starts with a bang – a visit to the ‘holy grail’ for geologists: Hutton’s Unconformity at Siccar Point. It is arguably the most important geosite in the world, as it was here, in 1788, that James Hutton stared into the abyss of time and was the first to realise the magnitude of geological time. At this site, it is possible to see the vertical layers of Silurian rock that would have originally been deposited as horizontal layers by turbidites in an ocean. When Avalonia collided with Laurentia in the Caledonian orogeny, these layers were folded and uplifted. Later in the Devonian period rivers deposited the horizontal layers and later still all the rocks were additionally tilted. All of these processes required a LONG time and this was the key fact that James Hutton realised. And so, the science of geology was born!
Other stops for the day included the Forth Rail Bridge (a World Heritage Site), crossing the Great Glen Fault and the Birnam Oak, of Shakespeare’s Macbeth fame! Our stop for the first night was in Aviemore, at the excellent Ravenscraig Guest House, where we were welcomed by hosts Helena and Scott.
Day two
We started the day with a fantastic breakfast at Ravenscraig (see photo below!) Aside from the food, the geological highlights of the day included the roche moutonées at Dulnain Bridge, Loch Ness, the Black Rock Gorge at Evanton, the Lairg meteor impact site and one of Scotland’s world class geosites: the Moine Thrust at Knockan Crag – the world’s first identified thrust fault. Loch Ness is the greatest lake by volume in the UK with more water than all the lakes in England and Wales combined. It is 23 miles long, 230m deep and is just 16m above sea level. It was formed by an Ice Age glacier eroding along the Great Glen Fault. The Great Glen Fault has had hundreds of miles of sinistral movement with the greatest displacement occurring in the late Silurian to early Devonian when England & Wales (part of Avalonia) collided with Scotland (part of Laurentia) to form the Caledonian Mountains.
We overnighted in Ullapool, returning to Harbour House, where we last stayed in 2019. It was nice to see host Alan and his team again.
Day three
We saw so much today all in the incredible North West Highlands Geopark. The group consensus was that our favourite stop of the day was the settlement of Clachtoll. Here we saw not only 1 billion-year-old Torridonian sandstone lying unconformably on 3 billion-year-old Lewisian gneiss, and at another location green glass embedded in the Torridonian sandstone (which was ejecta from the Lairg asteroid impact), but we also saw the recently discovered (2020) largest boulder in the world! The first picture below shows Clachtoll resident and my personal friend, Bill Smith, pointing to mudstone filled cracks the base of the 250,000 ton rock. The cracks formed when the boulder fell from a cliff a billion years ago forcing the mud it landed on up into the cracks! Other sights we saw today in this geological wonderland included: the Sole thrust fault at Stronechrubie Cliffs, Cambrian pipe rock at Loch Assynt, the Glencoul thrust fault, the multicoloured rock stop, Sango Beach mylonite, Smoo Cave, and the graveyard dyke at Scourie.
After some excellent pies from Lochinver Larder, eaten at Bill’s place in Clachtoll, we returned to Harbour House in Ullapool for a second night.
Day four
Today we left the North West Highlands Geopark and headed south to the Isle of Skye. At Elgol, we saw a large Paleogene dyke cutting through Jurassic sedimentary rocks (shown with the Black Cuillen in the background in the photo below). The peaks of the Black Cuillen form Britain’s most dramatic mountain range and are made of gabbro with some peridotite. The mountains have been shaped by Ice Age glaciation. The rock is the solidified magma chamber of the Skye volcano which has since been eroded away. The volcano was active in the Paleogene during the splitting of the North Atlantic, with the source of the volcanism being the hotspot that currently lies under Iceland. Other stops today included the Corrieshalloch Gorge and views of Eilean Donan Castle, but sadly our boat trip to Loch Coruisk in the Black Cuillen was cancelled due to strong winds.
Day five
A great geology day on the Isle of Skye with the theme being dinosaur trackways and the largest mass movement landslide in Britain. We visited a sauropod trackway at Duntulm, discovered in 2015, which is 170 million years old and most possibly the most important mid-Jurassic dinosaur trackway anywhere in the world. We also saw dinosaur prints at Brother’s Point and An Corran and had a guided tour of the Staffin dinosaur museum by Dugie Ross, the founder and curator. At the Quiraing we saw the Trotternish landslip where a 2km long block of Paleogene lava has slipped down on faults in the weaker Jurassic sediments beneath.
We then travelled on to Acharacle on the Ardnamurchan Peninsula, where we spent the night at The Loch Shiel Hotel, after enjoying dinner in their restaurant – amazing local seafood!
Day six
Today was a story of volcanoes. We started with a boat tour with Staffa Tours to the Isle of Staffa & the Treshnish Isles which are made from 55-58 million year old lava flows from the Mull volcano. For geologists and non-geologists alike, the star attraction of Staffa is Fingal’s Cave. The sea has eroded a fault which cuts spectacular basalt columns, that formed when the lava cooled slowly allowing the crystals to arrange themselves into the most space saving structure possible. In the Treshnish Isles we landed on Lunga and saw huge numbers of puffins, razorbills, fulmar and guillemots. During the boat journey, we were lucky enough to see dolphins, seals and minke whales. Later we visited the Ardnamurchan volcano, which is situated in the Lochaber Geopark, and saw its layered, saucer-shaped gabbro magma chambers that form rings best seen from a satellite view.
Day seven
Today was the final day of our Scotland geology tour. We spent the first part of day the Lochaber Geopark visiting the Ballachulish slate quarry and Glencoe. Glencoe’s magnificent scenery is the product of glacial erosion from the last Ice Age. Hanging valleys can be seen between The Three Sisters, shown in the first photo below, which empty into the main U-shaped valley in front. The rock was, however, formed in a Devonian supervolcano. The lower part of the mountains is a sill, the middle part is rhyolite lava flow and the top portion is ignimbrite deposited by huge pyroclastic flows. After leaving the geopark we visited East Kirkton quarry, the discovery site of the Romer’s Gap (early Carboniferous) tetrapod ‘Lizzie’ and, finally, Holyrood Park in Edinburgh to see Arthur’s Seat, a Carboniferous volcano.
Departure
After a geology-packed seven days, we all packed our bags and said goodbye to Scotland. It’s been a slightly different trip from ‘normal’, but we were all grateful for the chance to get out and about to see such a wide range of world class geology. Thank you to all the participants – it has been great to get back on the road again and to share this trip with you.
This trip (https://www.geoworldtravel.com/Scotland.php) will be happening again next year (twice!), although we only have limited availability for 2022 now. It will also be run again in 2023, so if you would like to join us then, please drop us a line: contact@geoworldtravel.com
Discussion about this post