The ocean between worlds
Beneath the rolling hills and estuary flats of the Anglo-Scottish border lies the scar of a vanished ocean. This scar, known as the Iapetus Suture, marks the collision zone where two ancient landmasses fused together around 420 million years ago. The land that now forms Scotland was part of a continent called Laurentia, which also included North America and Greenland. England and Wales were part of a separate microcontinent named Avalonia, which drifted north from near the South Pole.
Between them lay the Iapetus Ocean, which began to form around 600 million years ago and at its peak was over 1,000 kilometers wide. For millions of years, these two pieces of proto-Britain existed on opposite sides of a vast ocean basin in the Southern Hemisphere. The slow, relentless process of plate tectonics drove them towards each other. As the ocean floor was forced downwards, or subducted, beneath the continents, the Iapetus Ocean shrank. This geological drama, known as the Caledonian Orogeny, culminated in the final continental collision during the Silurian Period. The impact crumpled the continental edges, creating a mountain range once as high as the Himalayas. Today, the suture line runs from the Solway Firth on the west coast, through the Cheviot Hills, and out to the North Sea.