Sip back as we discover the Inner Hebrides of Scotland and explore Fingal’s Cave on the uninhabited Isle of Staffa designated a National Nature Reserve since 2001 and part of the local Hebridean Igneous Province and greater North Atlantic Palaeogene Igneous Province. This is story of the basalt columns and the remarkable natural acoustics of Fingal’s Cave or An Uamh Bhinn that have helped to explain how volcanic activity some 60 million years ago after the extinction of the dinosaurs and during the Paleocene the first epoch of the Paleogene Period helped to shape Scotland’s landscape that people wanted to visit.
The Isle of Staffa was named by the Vikings for its middle layers of geometric colonnades of basalt lava columns or pillars similar to those seen at the Giants Causeway in Northern Ireland and at Samsons Ribs at Arthur’s Seat in Edinburgh. The Isle of Staffa is a short boat trip from Iona, Fionnphort and Tobermory on the Isle of Mull or from Oban on the mainland and Kilchoan on the Scottish peninsula of Ardnamurchan, beside the Sound of Mull in Lochaber.
Fingal’s Cave has inspired works of literature, poetry and art and among the most familiar is the 1832 overture by German Composer Felix Mendelssohn titled, "The Hebrides" also known as "Fingal’s Cave" but was originally called Die einsame Insel or The Lonely Isle.
Mendelssohn visited the Isle of Staff in 1829 and was inspired to create a dramatic arrangement of music described as dark and majestic that captures the swell and feel of the Atlantic accompanied the the sound of waves crashing against rocks.
The Isle of Staffa has three distinctive layers that sit upon sedimentary rocks from the Triassic, Jurassic and Cretaceous periods. Starting with a base of compressed volcanic ash and dust called Tuff; a middle layer of basalt columns and an uppermost layer of jumbled and fractured columns and volcanic debris.
The Isle of Staff was formed primarily from the cooling and solidification of lava flows during the early stages of the Atlantic Ocean’s formation. Intense volcanic activity occurred as tectonic forces pulled apart the Eurasian and North American tectonic plates. This rifting process allowed vast quantities of magma to reach the Earth’s surface forming extensive lava fields across Scotland, Northern Ireland, and Iceland. The lava would have flowed in this area from the Mull volcanic centre making not only the Staffa Lava Formation but also the nearby Mull Plateau Lava Formation and the Mull Central Lava Formation.
The basalt columns of Fingal’s Cave are part of the same ancient lava flow that created the Giant’s Causeway in Northern Ireland located roughly 120 miles to the south. This shared origin highlights the interconnected nature of geological processes in the region. The lava that formed these structures middle and upper colonnades consist of dominantly 5, 6- and 7-sided basalt columns cooled relatively slowly, allowing the crystalline structure of the basalt to develop into regular hexagonal columns the hallmark of Fingal’s Cave.
As the molten basalt cooled it contracted it also fractured. These conditions were ideal for the phenomena of columnar jointing to happen forming a pavement of thousands of hexagonal columns. The fractures typically followed a hexagonal pattern because the structural integrity of a hexagon shape can distribute stress evenly because the 120-degree angles make it mechanically stable for the efficient and balanced release of surface tension in each direction during contraction as well as hexagons being the most common shape due to their efficiency in packing and symmetry.
On nearby Am Buachaille meaning "the herdsman" or "the shepherd" there is a pavement of twisted and irregular basalt columns known as an entablature. This type of columnar jointing in the lava flow would have formed near the top or in the middle of the flow and would have been heavily influenced by water and pressure from the gases produced in cooling travelling along cracks into the interior of the flow.
The size of the columns is influenced by the cooling rate of the lava. Rapid cooling typically produces smaller, more tightly packed columns, while slower cooling results in larger columns. In Fingal’s Cave, the columns average around 0.5 to 1 meter in diameter and can reach heights of up to 20 meters arranged in near-perfect vertical stacks.
The creation of Fingal’s Cave itself is a product of marine erosion. Over millions of years, relentless wave action exploited natural weaknesses in the basalt, such as fractures and joints, gradually enlarging the opening and carving out the cave. The combination of the cave’s natural geometry and the ocean’s rhythmic motion has created a structure with remarkable acoustics often likened to a natural cathedral.
The distinctive appearance of the Isle of Staff and Fingal’s today is the result of millions of years of weathering and erosion. During the Ice Ages, glaciers scoured the landscape, stripping away softer rock layers and exposing the basalt columns. Following the retreat of the ice, the pounding waves of the Atlantic Ocean further eroded the cliffs and columns revealing their geometric forms.
Fingal’s Cave is a must-see destination that holds an immense geological significance not only as a stunning example of columnar basalt but also as a window into Scotland's volcanic past. Its connection to the Giant’s Causeway underscores the extensive reach of the Paleogene volcanic activity and the shared geological heritage of the British Isles. The cave also provides insight into the processes of magma cooling, fracture formation, and coastal erosion, all of which contribute to our understanding of geomorphology.
The Staffa National Nature Reserve managed by the National Trust for Scotland ensures that the geological and ecological integrity of the island is preserved for future generations. While the cave’s resilient basalt columns are naturally durable the impact of tourism and climate change poses potential risks. Rising sea levels and increased storm intensity could accelerate erosion.