Torridonian facts for kids

Geological map of the Hebridean Terrane showing where Torridonian rocks are found

Mountains made of Torridonian sandstone

Exposed Torridonian sandstone

The Torridonian is a special type of sandstone found in Scotland. It's a sedimentary rock, which means it's made from tiny bits of older rocks, sand, and mud that settled and hardened over millions of years. This sandstone sits on top of some of the very oldest rocks in Scotland.

You can see the Torridonian sandstone on maps as orange areas. It's mostly on the western edge of mainland Scotland and also on parts of the Isle of Skye. This area is known as Wester Ross.

This sandstone is the oldest sedimentary rock in this part of the world. Below it, you'll find much older, harder rocks called gneiss. These ancient rocks are part of what's known as the Lewisian complex. All the rocks beneath the Torridonian sandstone were either formed from cooled lava (igneous) or changed by heat and pressure (metamorphosed).

How Torridonian Sandstone Formed

The Torridonian sandstones are often red. They were laid down by ancient rivers and lakes. This happened in a landscape that had low, rocky hills. Over a very long time, a huge amount of red sand was brought in by rivers. This sand slowly buried the old hills.

This process took place during the Proterozoic Eon. That was a super long time ago, roughly between 1.2 billion and 544 million years ago! There are actually two main groups of Torridonian sandstone, an older one and a younger one. There was a very long time between when these two groups formed. The lower, older sandstone group is a type of rock called breccia. This means it's made of broken, sharp pieces of even older rocks.

Where You Can Find It Today

Thick layers of sandstone exposed at the Old Man of Stoer

Over millions of years, the Earth's crust has moved and changed a lot. There have been times when the land pulled apart (this is called rifting). There were also times when huge forces pushed the land together, forming mountains (this is called mountain-building).

Because of these big changes, some of the Torridonian sandstone now lies hidden under the sea. Other parts of it have been pushed up high, forming the beautiful mountains we see in Scotland today.

Images for kids

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  Slioch mountain, made of Torridon Group sandstones, resting on older Lewisian gneiss around Loch Maree

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  Horizontally layered sandstones of the Torridon Group, forming the Horns of Beinn Alligin