Why There’s a Straight Line Through Scotland

Why There’s a Straight Line Through Scotland

[♪ INTRO] If you look at a map of Scotland, you’llnnotice an almost perfectly straight line through the Highlands that cuts from coastnto coast. This region is home to plenty of valleys andnpeaks, but this valley is eerily straight. Some interesting geology had to happen therenat some point. And it wasn’t just one event. About 520 million years ago, most of the Earth’snlandmass was split between two big continents: Laurentia andnGondwana. This meant the modern-day island of GreatnBritain was separated, with the north of Scotland sitting on Laurentia, and the southernnhalf of the island on Gondwana. Then, the two landmasses collided around 430nmillion years ago during a period known as the Caledonian Orogeny, which joinednthe two pieces through the collision forming the island we now know asnGreat Britain. This process resulted in the crumple and bucklenof the Earth’s crust which also formed new mountains and fault lines all aroundnthe world. One of those new faults was the Great Glen,nwhich is a strike-slip fault. This kind of fault happens when two tectonicnplates shear, or move horizontally, past each other. Other types of faults typically move one ofnthe plates vertically, which creates mountains and all kinds of elevated terrainnabove the fault. But because of how these two plates collidednwith each other during its formation, the pieces of the Great Glen Fault move horizontally. And they’ve actually moved a few times sincenthe formation of the fault. The Great Glen Fault has occasionally reactivatednand the two landmasses, Laurentia and Gondwana, moved anywhere fromn8 to 29 kilometers each time. This is a thing that faults do from time tontime to dissipate built-up stress. When force is applied by the two landmassesnpunching against each other, stress is created and when it reaches a tipping point,nthe plates shear and move in opposite directions, to relieve that built-upnstress. The biggest reactivation happened relativelynrecently, sometime in the last 66 million years, possiblynprompted by other parts of Earth’s crust spreading apart nearby. But why don’t we see straight lines likenthis more often? Well, these days, the Great Glen fault linenis even more visible due to a string of lakes, or lochs. That’s because most of the islands of GreatnBritain and Ireland were covered in enormous ice sheets during a handful of IcenAges over the last few hundred thousand years. The glaciers around the Great Glen startednreceding over 10,000 years ago, carving a deep valley along the fault linenthat actually goes below sea level, making that straight line through Scotlandneven more visible. So, this straight fault line is the productnof half a billion years of time and geology and it’s evidence of the large-scale eventsnthat formed Earth as we know it today! Thank you for watching this episode of SciShow! At this point, we’ve made thousands of educational videos over the years, and we’ve been able to offer them for free because of our patrons on Patreon. So, to all of our patrons, thank you for whatnyou do to make SciShow happen. If you’re not a patron but want to learnnmore about what that means, you can go to Patreon.com/SciShow. [♪ OUTRO]
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Why There\'s a Straight Line Through Scotland

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