Rock of the week - 1. Metamorphic rocks - Gneiss - the Lewisian Gneiss Complex скачать в хорошем качестве

Rock of the week - 1. Metamorphic rocks - Gneiss - the Lewisian Gneiss Complex

Week 1: Scottish rock of the Week - The Lewissian Gneiss Complex I thought I’d start off this series by talking about one of my absolute favourite rocks that you can find in Scotland which forms part of the oldest rocks in Britain. First of all, what is Gneiss? Gneiss is a high grade metamorphic rock that forms at high pressures and temperatures. When I say metamorphic rock, that just means it’s changed over geological time due to these high pressures and temperatures… where do we get this happening? Usually in big tectonic events that are associated with mountain building events so they can form in convergent plate boundaries where two plates come together which is known as regional metamorphism. Now the original rock type of the Lewissian Gneiss is thought to be manly igneous - granite and granodiorite that formed and has been dated back to an astonishing 3 billion years old which is madness because the earth is 4.6 billion years old so these rocks are very old. When we put these rocks at high pressures and temperatures and bury them, they change over time and the minerals ‘grow’, ‘align’ and ‘separate’ into compositional banding which forms these bands that we can see in the pictures of these rocks which is absolutely beautiful. The Lewissian Gneiss Complex is found in North West Highlands and outer Hebrides of Scotland, and represents the basement of what’s known as the Hebridean Terrane #geologist #geology #scottishgeologist #scottishgeology #tiktocksaboutrocks #reelsaboutrocks #tiktoksaboutrocks