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Carved from stone

Carved from stone Olivia Edward
01 Jun
2014
For her latest Royal Geographical Society (with IBG) Discovering Britain walk, Olivia Edward visits Shropshire to learn how glacial meltwater has shaped the history of one of England’s most picturesque market towns

For more great walks, trails and viewpoints, be sure to check out the new Discovering Britain Facebook page by clicking here.

Discovering BritainResidents of Ludlow might like to think that its reputation as a foodie haven lies all in the baking, the smoking, the roasting, the cooking, the animal rearing and the locals’ horticultural expertise. But there may be another reason why things in Ludlow taste so good: its soils. And these soils wouldn’t exist without the Ice Age, or ice ages, to be more exact.

During the past half a million years, two cold periods, or glaciations, engulfed the British Isles. The resulting glaciers carved out and ground up the countryside as they spread and then retreated.

The first and largest of these glaciations was the so-called Anglian Stage, which took place around 450,000 years ago. The ice sheet it brought covered nearly all of the area where Ludlow sits today – the border region known as the Welsh Marches.

The most recent, known in Britain as the Devensian, began around 120,000 years ago and ended 11,000 years ago. None of the glaciers of this latter period actually reached Ludlow, but three came very close and their meltwaters careered through the area, hollowing out channels and depositing sediments.

Before the Devensian period, the River Teme ran about ten kilometres west of the town

Evidence of the havoc that they wreaked on the landscape can be seen throughout this 5.5-kilometre walk, designed by geologist Michael Rosenbaum, who moved to the town around ten years ago to study its rocks and try to discover in detail how glaciation affected its scenery.

The first clue that something other than everyday erosion has shaped this landscape can be found at the start of the walk on Whitcliffe Common, from where it’s possible to look out over the picturesque vision of Ludlow, huddled on a hill below. ‘Notice how this piece of land we’re standing on is fairly flat and falls away steeply at one side,’ says Rosenbaum. ‘This sort of landscape feature is called a terrace and it would once have been the river’s floodplain.’

That was until glaciers altered the course and altitude of rivers in the area and sent dirty torrents of water raging across what was once a gentle slope. Before the Devensian period, the River Teme ran about ten kilometres west of the town, but when an enormous glacier blocked its path at Aymestrey, it was forced to move to its current course, which is much lower down – it takes us about ten minutes to walk down the hillside from the ancient river’s level to where today’s river flows.

Historically, the River Teme was central to the town’s development. Indeed, the name Ludlow is thought to come from the Old English for ‘place on a hill by a loud river’.

That noisiness is created by the rapids formed as water charges over hard rocks on the riverbed. This kept the watercourse shallow and fordable, which attracted the Romans, who tended to stride across rivers rather than build bridges.

The Normans were later drawn to the defensive properties of the eroded landscape – namely a small hill above a fast-flowing river – and built a castle on the ideal vantage point.

Rocks carried down in glacial meltwaters were used as cobbles along Ludlow’s main street during the early 19th century

Evidence of the force of the water that once rushed through this region can be seen down at river level. On the day I visit, the scene is tranquil: people drift out of one of the town’s renowned cafes after lunch, and on the riverbank, a woman and her grandson feed the ducks. But the exposed gravel by one of the town’s weirs hints at the Teme’s dramatic past. ‘Even in flood, today’s river wouldn’t be able to shift much more than sand,’ says Rosenbaum. ‘The gravels that you can see out there are the remains of a really powerful river containing glacial meltwater.’

These ancient rivers didn’t just have more power because of the volume of meltwater they contained. Sea levels dropped by around 120 metres at the time because much of the oceans’ usual water was trapped in glaciers and ice caps. The increased elevatory drop in the Teme’s total journey increased the river’s energy, causing more riverbed erosion and giving it a greater ability to transport sediment.

These Himalayan-style watercourses carried down stones that had been ground off hills and mountains farther north and west in Britain. When the river eventually slowed, the material it was carrying was released by the water and fell to the riverbed. And because rocks of similar sizes are deposited together, it’s as if they’ve already been graded ready for use by humans.

Rocks carried down in glacial meltwaters were used as cobbles along Ludlow’s main street during the early 19th century to discourage cattle from straying too close to the houses of the well off. They formed part of the engineer Thomas Telford’s redesign of the streets, which improved access to the town’s walled medieval centre.

You can tell that the cobbles have a fluvial history because they’re well rounded – all of their sharp edges were knocked off as they tumbled down the riverbed. Rosenbaum points out a few of the stones to me as we stand by one of Ludlow’s medieval gates next to a row of small Victorian terraced houses with window-box flowers waving in the spring breeze. ‘That one is granite – it would have come from the Lake District – and that one is a tuff, from the border of northwest Shropshire and Wales,’ he explains. Later, in a modern replica of the cobble verging at the railway station, he spots a fossil shell – all details that piece together the routes that these ancient rivers took across our landscape.

Much of the soil around Ludlow was also transported here around the time of the Ice Age

But not all of the glacial deposits were so large and lumpy. ‘They were quite a mixture,’ says Rosenbaum. Much of the soil around Ludlow was also transported here around the time of the Ice Age. It owes its nature to a type of deposit called loess, formed where silt is concentrated.

Silt is made up of particles that are about as small as a glacier can grind a rock down to, explains Rosenbaum. They’re of a similar size to flour, so they can be blown moderate distances and tend to pool together where it touches the ground. ‘That creates an ideal loam soil that farmers love,’ says Rosenbaum. ‘It’s good for both cattle and crops.’

Its popularity is down to the fact that it contains lots of minerals and traps moisture, which it releases slowly, so the ground doesn’t dry out during summer. Clay also retains water but does so almost too well, causing it to become sticky and unworkable. Sandy soil is more easily workable but dries out very quickly, leaving crops vulnerable to uprooting and damage. In contrast, loam retains just the right amount of water, remaining workable but moist. ‘Not much of Britain has these loamy soils,’ says Rosenbaum.

Murchison’s contribution – and the reason he came to Ludlow – was to establish the existence and order of the Silurian system

Smallholders and gardeners aren’t the only ones to have been lured to Ludlow by its unique geology. Roderick Impey Murchison, a renowned 19th-century geologist and one of the founding members of the Royal Geographical Society (and, for a number of years, its president), came to the area to study the greywacke or ‘transition’ rocks that lie under the local red sandstone.

Up until this period, it was largely believed that Noah’s flood was responsible for the mixed-up and erratic nature of European geology, such as large areas of gravel, fossils and rocks a long way from mountains. Some even went so far as to suggest that prehistoric beasts were found in the lower layers of rock because they were too heavy to climb aboard the ark and drowned, and that human remains were found in higher layers because they were the only animals with enough sense to rush to higher ground when the floods came.

Previously, scholars had used the ages of characters and timings of events in the Bible to string together a history of the planet that calculated its age at around 7,500 years. But Murchison, along with others working at the same time (including Adam Sedgwick and William Buckland), proved that the Earth was much older than originally thought and began to detail the layers of rock that made up the Earth’s crust.

Murchison’s contribution – and the reason he came to Ludlow – was to establish the existence and order of the Silurian system. Named after the Silures, a Celtic tribe from Wales, the Silurian is a series of sedimentary layers that date from 443 to 419 million years ago.

As Murchison and his colleagues began to piece together the history of the Earth’s surface, they realised that the various flood myths told by Christians, the ancient Mesopotamians and Hindus, among others, contained a grain of truth. Surging water had often shaped the landscape, although it was on a regional and local scale, and took place over an extended period, rather than on the epic and global scale as described in the biblical story of Noah and other tales.

Today, Ludlow’s loose fluvio-glacial deposits, such as those that form Bromfield Terrace on the outskirts of town, contribute to contemporary floods. Water flows quickly through them, which can cause Ludlow’s lower levels to flood. Indeed, the town’s recreation ground often spends part of the winter under water.

But the glaciers, and their meltwaters, have left Ludlow with plenty to be grateful for, including its attractive, undulating landscape, the soils that have helped it to become a destination for food-lovers, and the settlement-friendly hill and river that encouraged its establishment. Over the years, different eras of architecture have layered up inside the town – from a timber-fronted Jacobean coaching inn to grand Georgian homes and Victorian chapels, which attracted architectural historian Sir Nikolaus Pevsner’s appreciation, and led the poet Sir John Betjeman to declare that Ludlow was ‘probably the loveliest town in England’.

WALK Details
• Location: West Midlands
• Type: Urban
• Distance: 3.5 miles
Click here for more details

Unearth more of our nation’s history and find more great walks, trails and viewpoints around the UK at discoveringbritain.org or via the new Discovering Britain Facebook page.

This was published in the June 2014 edition of Geographical magazine.

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