The Parallel Roads (2)
Charles Darwin went to Glen Roy in Brae Lochaber in 1838. He was captivated by the parallel roads. He was of the opinion that they were maritime coastlines.
Darwin was of the opinion that the landmass of Scotland had risen greatly since marine waves were breaking in Glen Roy. An uplift happened three times because there are three shorelines.
Darwin expected that seashells would be found in the vicinity of the roads. But nobody found a single seashell.
Shortly after that, a geologist from Switzerland was in Scotland. He was Louis Agassiz. Agassiz reckoned that there were glaciers in Scotland a long time ago. In Glen Roy, he said that the parallel roads were not old maritime coastlines, but old coastlines on a large freshwater loch.
Here now is the picture that scientists have: About twelve thousand years ago, there was an ice age. A glacier was flowing from the high mountains around Ben Nevis.
The glacier grew larger. Eventually, it blocked the rivers in Glen Roy and Glen Spean. The glens filled with water. The water reached an altitude of 250 metres above sea level – or above sea level as it is today. The waves were breaking on that shore, forming the first ‘road’. That can be seen in both Glen Roy and Glen Spean.
The glacier expanded. It created a dam higher in Glen Roy, leaving a second shoreline at an altitude of 325 metres. In Glen Spean, the water was still escaping to the east and thus no second shoreline developed there.
But the growth of the ice at the mouth of Glen Roy continued. A third shoreline was developed on the great loch in the glen, at 350 metres. It would have been [was] an amazing sight when the weather warmed and the dam broke!
Na Rathaidean Co-shìnteach (2)
Chaidh Teàrlach Darwin a Ghleann Ruaidh ann am Bràigh Loch Abar ann an ochd ceud deug, trithead ’s a h-ochd (1838). Bha e air a bheò-ghlacadh leis na rathaidean co-shìnteach. Bha e dhen bheachd gur e cladaichean mara a bha annta.
Bha Darwin dhen bheachd gun robh tìr na h-Alba air èirigh gu mòr bhon a bha tuinn na mara a’ briseadh ann an Gleann Ruaidh. Thachair èirigh trì tursan oir tha trì cladaichean ann.
Bha Darwin an dùil gum biodh sligean-mara air an lorg an cois nan rathaidean. Ach cha do lorg duine slige-mhara sam bith.
Goirid an dèidh sin, bha eòlaiche-chreagan às an Eilbheis ann an Alba. B’ esan Louis Agassiz. Bha Agassiz dhen bheachd gun robh eigh-shruthan ann an Alba o chionn fhada. Ann an Gleann Ruaidh, thuirt e nach e seann chladaichean mara a bha sna rathaidean co-shìnteach, ach seann chladaichean air loch-uisge mòr.
Seo a-nise an dealbh a tha aig luchd-saidheans: Mu dhusan mìle bliadhna air ais, bha linn deighe ann. Bha eigh-shruth a’ sruthadh bho na beanntan àrda timcheall Beinn Nibheis.
Dh’fhàs an eigh-shruth na bu mhotha. Mu dheireadh, chuir e stad air na h-aibhnichean ann an Gleann Ruaidh agus Gleann Spiothain. Lìon na glinn le uisge. Ràinig an t-uisge àirde de dhà cheud is seasgad meatair os cionn na mara – no os cionn na mara mar a tha i an-diugh. Bha na tuinn a’ briseadh air a’ chladach sin, a’ dèanamh a’ chiad ‘rathad’. Tha sin ri fhaicinn an dà chuid ann an Gleann Ruaidh agus Gleann Spiothain.
Dh’fhàs an eigh-shruth. Rinn e dàm na b’ àirde ann an Gleann Ruaidh, a’ fàgail dàrna cladach aig àirde trì cheud, fichead ’s a còig meatair. Ann an Gleann Spiothain, bha an t-uisge fhathast a’ falbh don àird an ear agus mar sin cha robh dàrna cladach air a leasachadh ann.
Ach lean fàs na deighe aig beul Ghlinn Ruaidh. Chaidh treas cladach a leasachadh air an loch mhòr sa ghleann, aig trì cheud is caogad meatair. B’ e an sealladh iongantach nuair a dh’fhàs an aimsir na bu bhlàithe agus a bhris an dàm!
