The Silurian period, around 439 million years ago, has been well preserved nearby, in Wenlock Edge. During this time, Shropshire would have been flooded again by shallow sea. Wenlock Edge would have formed during this time, and the fossils of ancient corals and shellfish can be found all along the edge, preserved in limestone. Towards the end of the Silurian the Iapetus Ocean would have fully closed, and England and Scotland were joined. The closing of this ocean was important to geology in Great Britain. It caused most of our hills and mountains to align along the fault, northeast to the southwest.