The Yorkshire landscape we know and love today evolved over tens of millions of years. STEPHEN LEWIS dips into a fascinating book that follows the region’s geological history.

THE landscapes we grow up in seem to us eternal and unchanging. We plough and plant fields, chop down trees, build houses, delve deep beneath the earth for coal. But the brooding bulk of the moors, the majestic sweep of the Dales, the gentle warmth of the Vale of York and the rugged grandeur of the Yorkshire coast are forever.

Except that they are not. We can’t see it, because our lives are too brief. But over geological ages, the surface of the earth flows and cracks, dips and rises. What seems to us like the earth’s solid surface is in fact a thin, hard crust over a molten, superheated interior. Deep beneath our oceans, new crust is continually being formed as molten rock from beneath pushes up and out through great cracks, forcing apart some continents and driving others together so that they crumple and rise to form mountains.

The oldest rocks in Yorkshire date back more than 540 million years. Back then, the mass of land that is now the British Isles was part of a giant supercontinent anchored over the South Pole. In the hundreds of millions of years since, gradually that supercontinent has broken up, and the bits that made it up have floated off across the surface of the earth, sometimes colliding with other bits to form new continents.

Gradually, over those long, uncountable ages, what is now the British Isles has drifted north, coming to rest where we are today, part of the Eurasian landmass that is separated from the rest of the continent only by a shallow sea.

The story of that geological wandering is written in the rocks and landscapes that make up what we know as Yorkshire today. The limestone of the Dales, the chalk of the East Riding, the sandstone of the Vale of York and the Jurassic limestone of the North Yorkshire Coast, all are part of the story.

For geologist Paul Ensom, reading the tale told by the Yorkshire landscape is endlessly fascinating.

“Yorkshire has spectacular geology,” he says, in the introduction to his new book, Yorkshire Geology. “The rocks and the exhilarating landscapes they create contain information and stories of events spanning millions of years. Asteroids, colliding continents, volcanoes, huge rivers and catastrophic floods have all played their part….The landscapes of Yorkshire are the surface expression of this long and complex history.”

The oldest rocks in Yorkshire tend to be found in the west. That is because, over the last 65 million years, the gradual widening of the Atlantic has exerted pressure which has tipped the British Isles, lifting up the west and dipping the east. In the west of Yorkshire, including the Dales, there is therefore a lot of older, exposed rock: in the east, especially the East Riding, there tends to be much younger, sedimentary rock, including chalk.

Paul, who left the Yorkshire Museum in 1997 to move to the Natural History Museum in London, and who now works as a freelance museums consultant and geologist, stresses it is not as simple as that. Much of Yorkshire is covered by sediments such as sand and gravel deposited by glaciers and rivers during the comparatively recent ice ages.

But it is broadly true of the bedrock. And it is certainly true the oldest surface rocks in Yorkshire are found in the west of the county. These are hard, dark-coloured sedimentary rocks laid down as long as 542 million years ago, and can be seen, for example, on the “waterfalls walk” near Ingleton. These rocks were formed at the bottom of a sea when what is now Yorkshire was near the south pole. There was life, however, even back then long before the dinosaurs: fossils discovered include corals and marine trilobites.

Fast forward 200 million years. What is now the British Isles has drifted north to the equator, and has collided with what will become North America, Greenland and Scandinavia to form a new continent. The climate is tropical, sometimes dry, sometimes humid. But things change. Gradually, over millions of years, the seas creep across Yorkshire, before receding and encroaching again. Rivers, deltas and swamps form – and in the swamps forests grow, which ultimately form the coalfields of Selby and the rest of Yorkshire. Gradually, the land lifts again and becomes drier. The coal swamps dry out and the carboniferous era comes to an end 299 million years ago.

The next 50 million years are dry and arid. Stony and sandy deserts form across much of what is now Yorkshire. Large inland basins of water left behind when the seas retreated slowly evaporate, leaving behind them salt deposits. There is evidence of life in Yorkshire at the time, Paul says, especially around the margins of the retreating lakes – reptiles, insects and plant life among them. The legacy of the period today is the magnesium limestone and sandstone “red beds” beneath York and the Vale of York.

Then came the great age of the dinosaurs – the period between 199 and 65 million years ago when Yorkshire’s Jurassic coast and the Cretaceous chalks of East Yorkshire were laid down. What is now the British Isles had continued to drift northwards. The climate was sub-tropical, becoming almost Mediterranean, and much of Yorkshire was covered with warm, shallow seas. Limestone and chalk, made up from the skeletons of tiny microscopic sea creatures, was laid down on the bed of these shallow seas. And it is in the Jurassic limestone rocks in particular that we find some of Yorkshire’s most famous fossils – marine reptiles, Jurassic sharks, and the dinosaur footprints found around Scarborough and Whitby.

The way that Yorkshire looks today is largely the result of much more recent geological activity – particularly the ice ages, when glaciers swept down through the Vale of York, gouging out a deep valley but leaving the higher Pennines and North York Moors relatively unscathed.

But the much older history of the region is there to be read, if you know where to look.

Paul’s book, magnificently illustrated with stunning photographs, maps showing the drift of the continents, and artists’ sketches recreating what the landscape would have looked like in times long past, is a great place to start. There is a lot of information in its 169 pages. But dig around in here and there is a great story to be told.

Yorkshire Geology by Paul Ensom is published by The Dovecote Press, priced £22.50.