Geological Information

The landmass known today as Scotland was once connected to the area of the Torngat Mountain range of Labrador, Canada. This mountain range was part of the Grenville province, named for the Grenville orogeny during which it was created when the landmass now known as North America collided with Gondwanaland during the late Proterozoic Period (about 2 billion years ago). At that time "Scotland" was located nearly equidistant between the northern tip of Newfoundland and the southern tip of Greenland, situated northeast of the former and southeast of the latter.

The Great Glen is a strike-slip fault similar to the San Andreas fault of California (US). Because of compressional tension along faults, the rocks along such features are prone to developing fractures. Where such faults and their consequent fractures meet the surface of the land, water infiltrates the fractures. Freezing and thawing of this water, couples with its flow down slope, contributing to the acceleration of erosion that causes the development of the lochs of Scotland which display the characteristic southwest to northeast relative trajectory.

This type of loch formation should not be confused with the coastal lochs which display a predominance of glacial melt erosion features. As the glaciers melt, the newly unburdened lithosphere uplifts due to isostatic rebound in the dense, semifluid asthenosphere layer below. The resulting increase in the slope of the land surface accelerates meltwaters down slope, and the consequent saltatory transport of sediments increases, deepening the loch seaward.

Scotland and England were originally separated by a sea known as the Iapetus Ocean. The suture of Scotland to England occurred along the area of Hadrian's Wall. The two "parts of Scotland" however might be considered to be demarcated by the Lewisian (gneiss) deposits (of the Isle of Lewis, for instance) in the Northwest Foreland (The northwestern coast from River Donard south to encompass Coll and Tiree Islands and down to the southwestern most tip of the Isle of Mull--including Rum, Skye and the lesser inner Hebrides) and the landmass characterised by the Moinian surficial deposits of the Highlands north of the Great Glen fault. These surficial deposits converge along the Moine thrust faults - a fault line that runs from the southeastern most boundary of Skye and the Isle of Mull north, north east just east of Durness and the River Donard (also listed as the River Hope according to my maps). Anyway, you get the area of the basic line of the suture, I'm sure. Suffice to say that the entire area represents a convergent plate boundary where the basaltic oceanic plate is being subducted beneath the continental plate and the ancillary Island Arc of the Outer Hebrides is being rafted along towards a collision with the mainland (if one can call it that).

Further reading

For info on Scotland, see the Scottish information on this page
http://www.soton.ac.uk/~imw/Geology-Britain.htm

A formidable understanding of geological terms will be necessary to get the most out of the above paper. To that end, for education on geological technical terms one would do well to consult: http://www.ul.cs.cmu.edu/books/cont_techtonics/cont001.htm

For an informative elaboration of Scotland's geological history in terms understandable to most folks not particularly well versed in geological information consult:
http://www.iprs.ed.ac.uk/edit1/09/articles/06.html

A recommended book is Craig, G Y (ed.) "The Geology of Scotland", now in its 3rd edition, and full bibliographic details available from http://www.blackwell.co.uk/

Scottish FAQ > FAQ Contents > General information > Geological Information > Top