The Tertiary Period (65 ~ 0.85 million years ago)

The Tertiary was a very volcanically active period in Scotland’s geological history. Before the Tertiary, there was no Atlantic Ocean as Europe and America were part of the same vast continent. Due to the movement of the Earth’s tectonic plates at the beginning of the Tertiary, America began to move westwards, and Europe eastwards. A split grew between the two newly separating continents. As the continents continued to separate, the split continued to grow wider and eventually became the Atlantic Ocean.

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 Tertiary. Scotland's present outline has been drawn on the map to help you visualise where the Tertiary rocks that we find today were formed in relation to the surrounding continent and seas.

When continents separate in this way, volcanoes form along the split, creating new rock to ‘fill the gap’ or ‘rift’ between the drifting continents. There is currently a chain of underwater volcanoes running down the length of the Atlantic Ocean known as the Mid-Atlantic Ridge, but early in the Tertiary, this volcanic chain ran down what is now the west coast of Scotland. The islands of Skye, Rum, Mull, Arran and St. Kilda, along with the Ardnamurchan Peninsula were all volcanic centres (above sea level), and the remains of these volcanoes can be seen in parts of these areas. Although the volcanoes themselves no longer remain apparent, we see their lava flows and their eroded internal structures.