485 – 444 million years ago
During the Ordovician, Scotland lay far south of the equator and constituted the floor of an ocean called the Iapetus, just off the southern edge of a continent called Laurentia. Southern Scotland lay in the deepest water. Sand and mud was washed from the continent into the ocean, with the mud being transported the furthest offshore. The mud and sand formed very thick sequences of rock, which now form most of the Southern Uplands.
In the oceans, animals called graptolites thrived. Graptolites are extinct today, but their fossils are commonly found in the mudstones.
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 Ordovician. Scotland’s present outline has been drawn on the map to help you visualise where the Ordovician rocks that we find today were formed in relation to the surrounding continent and seas.