Country diary: these odd rocks wandered in with the ice age
Comfortably seated on the slopes below Glas Bheinn, I’m immersed in a view that stretches past the Assynt mountains to the sea. Then a chunk of pink quartzite by my boots draws my attention. Morphed by the Earth’s heat and pressure into something resembling cemented sugar, that rock sits in rosy contrast to the sombre grey stone below. Curious, I plant a finger on the geology map, to learn that the grey bedrock beneath my perch is ancient Lewisian gneiss. That pink stone at my feet has no source in sight.
Other anomalies decorate the surroundings, rocks of unexpected composition or situated in odd places: one boulder roosts on small rocks several inches above the ground, another leans over the cliff as if ready to take flight, isolated natural monoliths dot the horizon like watching beasts. They seem at once out of place yet integral to the setting, as if they wandered in from elsewhere to stay awhile. Which, in a sense, they did.
The quartzite and other strangely located stones are erratics, carried to their current position by ice-age glaciers, their name derived from the Latin errare, to wander, ramble, or stray. Twenty thousand years ago, ice buried the slope where I sit, the entire region a frozen mass with only the highest of peaks protruding above the glacial expanse, islands of earth in an ocean of white. The erratics are like glacial mementos, deposited hither and yon as the world revolved into a warmer time, and the ice melted, dropping its tokens on the scoured landscape below.
The pink chunk next to me stirs a memory. In the landscape below, I pinpoint where a 19th-century house is crumbling into the earth. Its drystone walls consist mainly of grey gneiss, yet I remember occasional quartzite sparkles amid the leaden hues, a contrast as delightfully surprising as the rosy rock on this slope. Once I thought the mason might have brought in quartzite from afar for reasons of luck or lore. Now, I think of an erratic, travelling by glacier, dropped during the melt, picked up by human hands and placed in the wall, its journey continuing well beyond its ice age wanderings.