After the Ice
Whether the glacial period has ended is a moot point; hence, technically, the present period is called the 'Holocene Interglacial'. Over the last 10,000 years, since the disappearance of the ice, Scotland has experienced some variation in its climate, which has affected the landforms. But these changes are much smaller than those which occurred during the Ice Age.
Throughout the period after the ice had melted, the debris left by the ice and the meltwater has been reworked. In the river valleys, sequences of terraces have been formed as the rivers adjusted to fluctuating, but generally lower discharges. Abandoned channels are often clearly visible on them and large alluvial fans have been deposited from side valleys onto the terrace edges.
Some rivers have, naturally, continued to flood the surrounding land. Also material on slopes has continued to move downslope. Sometimes it moves in a rapid fashion especially after heavy rain in the form of landslides or debris flows. At other times movement is slower and piles against the upslope sides of drystane dykes.
Land covered by ice had no traces of soil and vegetation but we know from examination of pollen records that vegetation began to spread over the surface again from about 13,500 years ago. The speed of plant colonisation and soil development was affected by the fluctuations in climate, being held back during cold spells such as those which occurred 11-10,000 years ago, and by the acidity of surface material. Crowberry, birch and willow were early colonisers, often succeeded by ash and hazel and later by oak, elm and pine. With the advent of wetter periods, perhaps aided by the early tree felling activities of humans, came the development of peat, in many parts of the Highlands (especially the blanket bogs of Caithness and Sutherland), as well as the extensive lowland raised bogs in Central Scotland. At the same time, extensive heathlands were developing.
The development of soil and the colonisation of vegetation meant that the land surface became much more stable, and limited the amount of debris carried down the river valleys to the coast and into the sea.
One of the most dramatic changes after the ice was the changing position of relative sea level. It has varied around Scotland, probably rising all the time in Orkney, Shetland and the Western Isles over the last 10,000 years, but elsewhere falling, then rising and then falling again. With the melting of the last ice cap, the areas depressed under its weight began to rise. The greatest uplift centred on Rannoch Moor, whereas other areas at the geographical extremities of Britain, for example, Shetland and the southeast of England, rose less or sank. At the same time, the sea level rose because of the melting of the ice globally. The variation in ice thickness in different parts of Scotland means that the amount of uplift of the land varied considerably. Hence, remnants of the higher sea levels are found at different altitudes in different parts of the country; for example, 14m in the Inner Clyde compared with 6m in the Moray Firth.
The sea level rise after the Ice Age reached its maximum around 6-7,000 years ago. The level then stayed relatively stable for up to 1,000 years before it fell gradually to its present level as the land continued to rise.
Layers of sediment which accumulated in caves near Assynt during the Ice Age have preserved important clues about these environments. The bones of animals no longer found in Britain, including the brown bear, reindeer, lynx and wolf, have been found. Careful detective work on these cave deposits and on pollen records from nearby sites has allowed an accurate reconstruction to be made of this area of the Northwest Highlands from the end of the Ice Age to the present day.