The Silurian Period (443 ~ 416 million years ago)

During the Silurian, Scotland lay south of the equator on the southern edge of a continent called Laurentia, to the south of which lay an ocean called the Iapetus. On the opposite side of the ocean lay the continent called Baltica, with England on its northern shore. The two continents were slowly moving towards each other and as they did so, the ocean between them was closing. By the end of the Silurian, the two continents eventually collided and the ocean disappeared. It was at this point that Scotland and England came together.

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Scotland hasn't always been on the same postion on the face of the Earth and has not always had the same outline. This map * shows how 'Scotland' may have looked during the Silurian. Scotland's present outline has been drawn on the map to help you visualise where the Silurian rocks that we find today were formed in relation to the surrounding continent and seas.

Before the ocean had finally closed, northern Scotland lay above sea level and southern Scotland constituted the ocean floor. Sand and mud was washed into the ocean from the land and formed very thick sequences of shale and muddy sandstones (known as ‘greywackes’). The youngest Silurian rocks show the change from sedimentary rocks formed in a marine environment, through to rocks formed on land, in rivers and lakes – as the land emerged from the sea. Silurian rocks form a large part of the Southern Uplands. The fossil remains found include trilobites, shellfish and early jawless fish, most if not all of which are now extinct.