145 – 66 million years ago

During the Cretaceous, a global rise in sea level led to much of Scotland being covered by a shallow, warm sea. The non-mountainous regions of Scotland, drowned by the sea, were blanketed in a layer of chalk, a white sedimentary rock made from the internal skeletons of marine micro-organisms.

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

This map is a schematic reconstruction of what Scotland MAY have looked like at a particular point during the Cretaceous – it is only a representation of Scotland’s ancient palaegeography, not the most accurate scientific palaeogeographic reconstruction. (c) Image reproduced by kind permission of The trustees National Museums Scotland

In Scotland, most of this Cretaceous rock has since been eroded during the Cenozoic era, unlike in England where Cretaceous rocks are far more extensive. Today, only tiny outcrops of Cretaceous rocks remain, found mostly in the west of the Scottish mainland and in the Hebrides.