The Wild West / The Glaciation of Loch Morar

Glaciation

Everybody has heard about the ice age, usually from half forgotten Geography lessons from teachers with unfathomable nicknames, but how many of us stop to think about what it must have been like, try and visualise these gargantuan events?

We are told that between 11,000 and 10,000 years ago up to 4000ft ice covered the mountains of Scotland and huge glaciers grinded and pummelled their way westwards to the coast. Huge valleys were created, rivers diverted, the landscape changed forever. Even the level of the sea was changed!

All traces of these vast ice fields have long since vanished and all we have is the word of scientists that these events really happened… Or do we? Are there clues hidden in the landscape waiting to be read, waiting to tell a story of events long passed?

In fact here in Morar, you could not be better placed to take a close look at these clues yourself, and then ponder and draw your own conclusions.

So let's take a closer look at that evidence.

The Big Water

Loch Morar itself. What a strange and eerie piece of water. Twelve miles long and a mile wide, over a thousand feet deep and yet only yards form the ocean with its' surface just a few feet above sea level. To reach the same subterranean depths as on the murky floor of Loch Morar, it would be necessary to travel out beyond St. Kilda, far beyond the Western Isles and into the deep Atlantic itself.

If Gustav had built another of his towers on the bottom of Loch Morar, we would not know it was there as not even the very tip would beak the surface. Loch Morar is as deep as the mountains that surround it are high; the deepest piece of inland water in Northern Europe and indeed the 17th deepest lake in the world. There is enough water in the loch to give every single person on the planet a glass of water every day for the rest of their lives!

What forces could have created such an almost bottomless basin so close to the sea?

Hydrographic Profile of Loch Morar from West to East

The profile of Loch Morar gives us some clues as to the forces that created it.

Imagine a glacier such as we see in the Alps today, but here in Scotland, moving slowly from the ice clad mountains to the east, it's immense weight gouging a massive furrow in the surface of the earth, later to be filled with water as the ice receded.

Such a river of ice would carry before it a morass of sediments from the valley floor, scraped up as the glacier advanced and then dumped at the furthest extremity of it's' advance. A “terminal moraine” as described by glaciologists.

The western limit of Loch Morar is blocked by a huge boggy expanse of peat and sediments known as the “Mointeach Mhor” or the “smooth mile”. This “terminal moraine”, a wall of sediments marks the furthest extent of the now vanished Loch Morar glacier. The original river course, now blocked by the glacial deposits was squeezed into the North West corner where it outflows over a steep series of rocky steps known as the falls of Morar.

Ferries and Bridges

Take a look at a map of the west coast of Scotland. Isn't it odd that virtually every sea loch on the western seaboard from Loch Etive in the South all the way to Loch Glencoul in the North have a similar shape. A deep inner basin, shallowing towards the west where there is a severe narrows before broadening and deepening once more into the open sea.

Lochs in Western Scotland

How convenient that each long arm of these east-west running deeply incised flooded valleys has a convenient narrow point near the coast for engineers to build bridges or run ferries across. Loch Etive and the Connel bridge, Loch Leven and the Ballahulish Bridge, Loch Linnhe, the Corran ferry. So it goes on all the way up the coast including Loch Ailort, Loch Nevis, Loch Hourn, Loch Duich and Loch Glencoul. Why do the shapes of the west coast lochs mimic each other?

Think once more of huge rivers of ice, grinding and gouging their way towards the west, deepening the valleys down which they flow to a depth far below the work of even the wildest and most aggressive mountain torrent.

Eventually these rivers of ice reach the sea. You can almost hear the rocks on the bottom of the tortured valleys breath a sigh of relief as the huge weight is lifted off them. The ice floats! Suddenly the colossal erosional forces are removed as the oceans waters take on the burden of the glaciers' mammoth weight.

With the weight of the glacier removed, the ice no longer gouges away at the valley floor resulting in a gradual shallowing of the eroded basin and, as if by magic a sharp narrowing of the waters results: And those bridge builders are kept happy.

Loch Morar fits this design in all but one respect, the outlet to the sea became blocked by the debris of the glacier that created it.

Bathymetric Profile of Loch Morar from West to East

More Ice Please

If these deeply incised west coast valleys are indeed the result of erosion by glaciers, it would be reasonable to suppose that where two glaciers joined together, the valley floor beneath would show evidence of a sudden deepening reflecting the increased erosional force at that point.

At the head of Loch Morar, two valleys, Glen Pean and Abhainn Rath enter the loch below Sron. A look at the profile of the loch floor does show a remarkable sudden increase in depth at this point. A mile or so further west where Glen Taodhail joins Loch Morar there is a further deepening and then, half way down the loch, the Meoble valley enters the loch from the south. Immediately adjacent is the deepest piece of water of all!

A few miles over the hills to the south, another deeply eroded valley containing Loch Beoraid shows a similar profile where the two valleys of Gleann Donn and Ruighe Breac meet at its eastern end.

Bathymetric Profile of Loch Beoraid from West to East

There is evidence here that the shallowing at the midpoint of the loch is also related to the floating of the ice suggesting that seawater extended not just into Loch Morar, but also all the way up the Meoble valley to Loch Beoraid.

Did glaciers once move down these valleys? The river that flows gently north from Loch Beoraid to Loch Morar is pleasant enough, but could it ever have had the power to cut such a wide and luxurious valley? The same could be said for the rivers at the head of Loch Morar, they hardly fit the valleys in which they lie. Were these valleys in fact carved by ice?

Raised Beaches

Glacialologists postulate that the mass of ice that covered what is now the Scottish Highlands caused the whole of the North West of Scotland to become depressed, to sink down into the plastic mantle that lies beneath the earths crust. At the same time the South East of the UK would have tilted a little higher in sympathy.

With the end of the ice age it would be natural to assume that the melting ice would cause the sea level to rise, though by how many feet it is difficult to be sure. However it is suggested that any rise in sea level would be offset by a gradual re-adjustment as the whole of the UK, relieved of it's icy burden would return to it's pre-ice age level.

Such a theory would result in an apparent rise in sea level in the South East of the UK and a corresponding fall in apparent sea level in the North west of Scotland.

The construction of the Thames barrage in London was deemed necessary to protect the capital from the ever increasing threat of flooding caused by ever rising spring tides, but is there any evidence of the corresponding apparent falling sea levels here in the North West?

Straight Lines in Nature

One of my favourite houses in the village is Bourblach. With it's commanding elevated position on the North side of Morar bay and surrounded by attractive level ground it occupies an idyllic location.

The ledge on which Bourblach stands can be seen running all the way around the bay, completely horizontal, with a few interruptions where rivers cut through it. Behind are frequent outcrops of rocks forming small cliffs, some with apparently water worn caves cut into them.

Raised Beach at Bourblach

Close examination will reveal an abundance of rounded pebbles, such as those found 68ft below on beaches where constant wave action rolls the stones together until all sharp corners are removed. A 68ft “raised beach” has been identified along much of the North West coast of Scotland suggesting that sea levels in the past were indeed much higher than they are today.

If the house at Bourblach had been standing 10,000 years ago, would the gentle shores of the Atlantic been lapping at the front door?

If sea level was indeed 60ft or so higher than its' current levels, then it is probable that Loch Morar was once connected to the sea. Marine algae have indeed been found in bottom cores performed in late 1970s proving that seawater once swept into the loch bringing with it marine life, and who knows, even a monster or two!

So next time when taking a stroll in the magnificent scenery that surrounds us, take a second look and give a thought to the forces of nature that have contrived to produce the landscape that we see today. There is evidence of glaciation over much of western Scotland. But nowhere is it better presented than here in Morar.