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Moving Mountains - Geology

Bedshiel Esker, formed from gravel deposited by a sub-glacial stream.
Bedshiel Esker, formed from
gravel deposited by a
sub-glacial stream.

Southern Scotland is moving, albeit infinitesimally slowly, edging north-eastwards. Its extraordinary journey started more than 500 million years ago, when Scotland was part of a landmass lying to the south of the equator. This slowly drifted north, passing through the tropics, before fragmenting into today's continents and islands.

The present is the key to the past and the past is the key to the future"
James Hutton

500 million years ago: Marine sediments were laid down on the bottom of an ancient deep sea, the Iapetus Ocean, which started to shrink as two landmasses lying on either side drifted towards each other.

430 million years ago: These landmasses, with the early incarnations of Scotland and England, collided. As the ocean disappeared and the lands merged, the marine sediments were compressed, raised and folded into a mountain chain that forms the foundation of the Southern Uplands. The Southern Upland Fault marks the northern boundary of this range.

410-360 million years ago: This mountain chain experienced the hot desert conditions of the southern tropics. Short-lived rivers caused rapid erosion, creating the Old Red Sandstones that later turned into the rich red soils of Nithsdale, Lauderdale and East Lothian. Sporadic volcanic activity created the granite and basalt hills of the Galloway Hills, Cheviots, Pentlands and the remnant volcano hills of the Eildons and East Lothian Laws and coastal islands.

340-300 million years ago: Sandstones and fossil-rich coral reef limestones were laid down in shallow tropical lagoons, deltas and seas and small basins of coal formed in steamy forested swamps.

250 million years ago: Violent earthquakes fractured the rocks along major faults, as continental movements tilted and folded layers of rock into new mountains. Thereafter, southern Scotland was mainly dry land but river erosion and weathering wore down softer rocks and revealed deeper, older, harder rocks.

2 million years ago: The Ice Age began and until just 12,000 years ago, this landscape was shaped by repeated glaciations. Ice sheets, hundreds of metres thick, rounded lower mountain tops, carved corries and crags on higher peaks and created flat-bottomed valleys. As the last ice sheet retreated, meltwater rivers cut large valleys. Thick layers of boulder clay, sand and gravel were dumped over the bedrock, with clusters of streamlined oval hillocks (drumlins), sinuous gravel ridges (eskers) and crag-and-tails scattered over the landscape.


Useful links:

www.scottishgeology.com

 

 

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