What is the giant scar that cuts across Scotland and is visible from space?

Daily Record

4 days ago

Satellite images of Scotland reveal a huge crevice that cuts across the Highlands- but what is it?
Formed hundreds of millions of years ago, a huge crater in the landscape of Scotland cuts across the upper reaches of the land from northeast to southwest. Visible on most satellite images of the country, it appears as a line cutting diagonally across the Highlands.
But what exactly is this huge line on the map, and how was it formed? Known as the Great Glen Fault, this geological phenomenon serves as a reminder that we live on an ancient planet whose history is reflected in our landscape.
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The fault tells a story of the land that has had a huge impact on Scotland's human and geological history. Here's everything you need to know about this giant crater that cuts deep into the core of Scotland's past.
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What is the Great Glen Fault?
The Great Glen Fault is a deep scar in the land which is visible from space. It first formed around 430-390 million years ago, and cuts diagonally across the country between Fort William and Inverness.
It is the most prominent fault in the UK, and was formed by a series of earthquakes.
The fault line was eroded by glaciers more than 10,000 years ago, which deepened the long crater to below current sea levels, creating a series of lochs, including Loch Ness.
It lines up almost exactly with the Great Glen, a 62-mile valley also running from Inverness to Fort William.
A popular long-distance walk, the Great Glen Way largely follows the fault line of this famous strip of land for 75 miles.
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How was the Great Glen Fault first formed?
The Caledonian Orogeny (430-390 million years ago) was a period where the landscape changed significantly, due to the moving of tectonic plates and subsequent earthquakes.
The Great Glen Fault formed towards the end of this period, when the Laurentia and Baltic tectonic plates collided, which moved the rocks on either side about 62 miles past each other.
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In scientific terms, the Great Glen Fault is known as a strike-slip or wrench fault. According to Britannica, this type of fault is a fracture in the rocks of the Earth's crust where the tectonic plates slip past each other, parallel to where they have collided.
Strike-slip faults can be either right-lateral (dextral) or left-lateral (sinistral), depending on the direction the opposite block of land appears to have moved.
According to previous studies, the Great Glen Fault developed as a left-lateral strike-slip fault during the Caledonian Orogeny.
However, it then reactivated right-laterally in the Tertiary period (65-5.2 million years ago), when the tectonic plates moved again.
Is the Great Glen Fault still active?
According to Historic Mysteries, there has been activity in the Great Glen Fault as recently as 2021.
While we don't often see earthquakes in Scotland, there have been around a dozen recorded since 1816, when the largest known tremor with a magnitude of 5.1 was recorded near Inverness.
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