WILLIAM PENGELLY CAVE STUDIES TRUST

THE DEVONIAN PERIOD

THE DEVONIAN SEA DELTA

Reconstruction of conditions in south-west England during the Devonian Period 375 million years ago. The erupting volcanoes built shallow sea floors on which coral colonies grew.

Poisonous gases from the volcanoes later killed the coral organisms and their limey remains became compacted to form the limestone rock which we see in Higher Kiln Quarry.

THE DEVONIAN SEA

During The Devonian Period 350-400 million years ago the southern land mass of England as we know it today then formed the bed of a large sea - the Devonian Sea, which stretched from Devon and Cornwall to the Ardennes in France.

The Northern shoreline of the Devonian Sea was located near the present day Bristol Channel and the land-mass to the north, named the Old Red Sandstone Continent, was desert-like in appearance with a limited animal and plant life.

The rocks of this land mass were eroded away and the debris carried by rivers to form the bed of the Devonian Sea. These later became compacted and altered to form the beds of slate which now underlie Buckfastleigh Hill.

LIFE IN THE DEVONIAN SEA

This period marked a significant step in the evolution of life on earth. Before the Devonian, the land had been barren while the sea teemed with life. Suddenly within the space of a few million years, the land evolved into a fertile haven for any animal which walked upon it. The earliest vertebrates, animals with backbones, appeared in the form of heavily armoured fish-like creatures which swam in the freshwater rivers and lakes. Within 50 million years some of these fish had developed primitive lungs and began to make their way out onto the land to become the first true amphibians.

On the shores of the rivers and deltas plants began to spring up out of the water and evolve into primitive land plants. Eventually huge forests appeared, with giant tree-like ferns and club-mosses covered with green needle-like leaves.

Fossils, the preserved remains of prehistoric animals and plants, are often used to determine the type of environment which existed millions of years ago.

If we study the fossils found in Devonian rocks we find that the Devonian environment 360 million years ago varied from desert-like continent on which existed primitive vascular plants to a deep sea with coral banks.