Created in fire, sculpted by ice - SCOTLAND
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Part eight
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Around 20,000 years ago — a moment in geological time — Scotland lay beneath an immense sheet of ice, towering more than twenty times the height of the Wallace Monument. Evidence of this glaciation is visible everywhere today: in the shapes of hills and glens, in corries and sea lochs, along the coastline, and even in the soils of our gardens.
The Ice Age did not occur in a single block. Its influence swung back and forth like a pendulum, with warmer intervals bringing climates similar to those we experience now. In fact, we still live within an Ice Age; we are simply in one of its warmer phases. Over the last 700,000 years, Scotland was buried under deep ice at least five or six times, and the long‑term cycle suggests that another major glaciation will eventually return. Glaciers may reappear in the Highlands in a few thousand years, though full ice‑sheet coverage is likely tens of thousands of years away — and global warming may delay it further.
During the last major glacial period, a vast ice sheet up to 1,400 metres thick covered the landscape, with only a few of the highest mountains in the North West rising above it. In warmer intervals, smaller corrie glaciers carved the dramatic Alpine forms of the Cuillin, Rum, and Arran hills.
Across the Lowlands, glaciers spread a blanket of till — boulder clay — over the land. In the Tweed Valley and Solway areas, this clay was moulded into low, rounded hills known as drumlins. Much of Glasgow is built upon a wide field of these drumlins.
As the ice melted, enormous volumes of water cut channels into the bedrock, forming dry valleys on the northern flanks of the Moorfoot Hills and Lammermuirs, and on the northern slopes of the Cairngorms. On lower ground, meltwater deposited sand and gravel in mounds, ridges, and terraces, particularly around Inverness, in northeast Fife, and in a belt stretching between Lanark and Edinburgh.
By about 12,000 BC, most of the last ice sheet had melted. Then the Gulf Stream weakened, triggering a sudden return to colder conditions. Glaciers expanded once more in the Highlands, leaving behind moraines — heaps of rocky debris still visible in glens and across Rannoch Moor. This final cold phase ended abruptly around 9,500 BC, when the climate shifted into the interglacial conditions we experience today.
The advance and retreat of ice sheets caused land and sea levels to rise and fall. The weight of the ice pressed the land downward, and as the ice retreated, the land rose again. These movements created the raised beaches seen on Islay, Jura, and along the East Coast — areas that later became ideal ground for links golf courses.
As the great ice masses shifted, the underlying rocks adjusted. During the later stages of the glacial period, the North Sea bed rose above sea level and became dry land covered in tundra. Mainland Europe extended as far as the Shetland hills, and rivers from eastern Scotland flowed across this tundra into a deep inlet off the coast of Norway.
As temperatures increased, the ice melted gradually, leaving ridges and hummocks of gravel and sand across Scotland. The oceans refilled, and by 12,000 BC the massive ice sheets had largely disappeared. With the weight of ice gone, Scotland rose, while the former North Sea lands slowly subsided. Reindeer — and possibly wild horses and giant deer — roamed the shrinking landmass that connected northern Scotland to the wider continent. Temperatures dipped once more, allowing ice to rebuild briefly in the western mountains, but by around 9,500 BC the glaciers had vanished for good as temperatures climbed above modern levels.