Where is chalk found

Seas rose rapidly, and one third of the landmasses present today disappeared beneath the rising waves. In regions where chalk is found today, the water was filled with billions of microscopic organisms called coccoliths.

When they died, their skeletons sank down through the clear water, in such quantity that in places the ocean would have turned a milky blue. On the ocean floor the skeletons piled up, forming a soft ooze.

Over time, this compacted and hardened — living bones translated into white rock. The uniformity of the chalk — these massive thicknesses of rock, some a mile in depth — is testament to a stable, slowly drifting world where, for millions of years, nothing much happened. During the late 19th century, geologists began further refining the existing rock units of type and time.

But relatively little attention was paid to chalk. It had some use as a fertiliser and, later, in concrete, but it contains no coal, oil, precious minerals or metals, and is generally too soft to be a building material. Even among that subsection of the population who get excited by a good piece of rock, for years chalk was seen as fairly dull.

In Britain — or, more accurately, the place that was to become Britain — the next big thing to happen to the chalk occurred about 50 million years ago, when the African plate crashed into Europe. The land buckled up, forming a series of ridges including the Pyrenees and the Alps. In Britain, a series of low chalk hills began to emerge from the sea. At first they were capped with mud and sandstones, but erosion eventually did its work and formed the bare chalk scarps of the South and North Downs and the Chilterns.

Smooth, rolling hills covered with short turf. Gentle slopes and steep escarpments, dry valleys and lonely beech hangers. Seen from a distance, it seems to ebb and swell like the ocean from which it once emerged. On postcards and tea towels, images of chalk landscapes perform a particular version of Englishness.

At the edge of the country, the chalk becomes dramatic, unsettling. Standing on the beach at Cuckmere Haven in Sussex, you look up at the towering whiteness and it seems for a moment as though it is falling towards you out of the blue sky. The exposed chalk has something cold and otherworldly about it. To see such whiteness, such brightness, feels unnatural. These were much painted by Monet, Pissarro and Renoir. Chalk, which the English often seem to regard as peculiarly their own, lies under much of northern France, and bits of Scandinavia, the Netherlands and Germany.

In , Richard Selley, then a professor at Imperial College London, had been thinking about the similarities between the chalk landscape of the North Downs and the Champagne region in north-east France. His neighbour had been unsuccessfully trying to farm sheep and pigs on his estate in the North Downs.

Selley suggested he try sparkling wine. That vineyard now produces close to 1m bottles of wine a year, about half of it sparkling — which would, if made in north-eastern France, be called champagne. T he Chiltern Hills run for 46 miles in a south-west to north-east diagonal from Goring-on-Thames in Oxfordshire to Hitchin in Hertfordshire. At their highest point — Haddington Hill in Buckinghamshire — a stone monument marks the metre summit.

Much of this landscape is farmland. There are small villages huddled deep in the dry valleys, historic market towns and the edges of suburbia. I joined Farrant and his BGS colleagues there on a warm day of blue skies and strong, low autumn light. Farrant and I set off with a new recruit called Romaine Graham, who had been working on the chalk for two weeks and had blood blisters on the palms of her hands from wielding her hammer.

We climbed over a barbed-wire fence between two ploughed fields; where there are no footpaths, the surveyors rely on the goodwill of landowners for access. Farmers are usually OK, but gamekeepers tend to be territorial. By the edge of the field, Farrant and Graham used their hammers to break open pieces of chalk. We know now that the chalk was never just the three large, monolithic blocks of rock and time that the 19th-century geologists proposed — Lower, Middle and Upper.

In the s, geologists began subdividing the chalk into nine formations. As we walked, Farrant and Graham began to discuss differences between formations.

To the uninitiated, these can seem negligible. Working in chalk is all about getting your eye in, reading the subtlest of clues. The Seaford, by contrast, is soft, smooth and bright white, and often contains large flints. The Holywell is creamy white, filled with small fossils.

The Lewes is white, creamy or yellowish. Chalk rock is very hard, closer to the hard limestones of Cheddar Gorge than the soft, crumbly white stuff that most of us think of as chalk. Each formation represents a different world, and each of these worlds existed for far, far longer than humans have been on the planet. W here there are not many outcrops, the surveyor must find other ways of getting at the chalk.

Buchanan, R. Everhart, M. Hattin, D. Niobrara chalk in Logan County Chalk, a sedimentary rock , is a soft form of limestone that is not well cemented and thus is often powdery and brittle. Flints are common along certain areas of the Jurassic Coast where the chalk outcrops. Below is a picture of flint embedded in the chalk at Lulworth Cove. For a long time the boundaries between the Lower, Middle, and Upper Chalk were determined by the abundance of flints before they were adjusted to where they are now Wright The Upper Chalk contains an abundance of flints, while the Lower Chalk completely lacks flints Bennison Flint generally forms near the surface of the earth in a low pressure, low temperature environment Chesterman It contains no crystals and has a hardness of 7 on a scale of 1 to 10, with 10 being the hardest substance on earth Chesterman Flint is commonly found on the surface of the chalk because as the softer chalk erodes away the hard flint pieces are left on top Oxford Museum 8 Aug Flint filled in burrow holes in the chalk, allowing these to be preserved in areas that the burrow holes normally would be indistinct Melville In the town of Beer flint has been used as a local building tool due to its durability and availability Brunsden However, there is a great deal of controversy about whether or not it would be wise to remove these flints because they are actually very good at preventing erosion of the chalk cliffs Ensom At Old Harry Rocks the chalk has been eroded extensively.

Waves will find weaknesses in the rocks and will erode these areas until they form arches or caves. These then continue to erode until the arch collapses and there becomes a tall island of chalk called a stack. Finally, the chalk stack or needle a stack that comes to a point will be eroded to the point that they collapse completely Brunsden As recently as a few thousand years ago the area around Old Harry Rocks was connected to the Isle of Wight , but they are now separated by the English Channel Brunsden As of , a person could climb out to Old Harry Rocks which are now considered to be a stack of rock not connected to the rest of the chalk West In , the Wife of Old Harry, another chalk stack, collapsed West However, it is important to note that while some of the chalk formations are collapsing, others are constantly being created as the waves continue to erode weaknesses in the rock West Eventually the small arch in the rocks on the left will look like the rocks on the right.

Clearly, these land forms are in a constant state of erosion and change. Several small faults and joints can be seen in this area but they are not big enough to indicate any sort of major tectonic activity West There is some major faulting within the chalk, though not seen at Old Harry Rocks. At Ballard Point the chalk is curved to a near-vertical orientation and this can be viewed by boat from the English Channel West The chalk above the faulting is from the Upper Chalk and is 76 meters thick West Image from West The thrust fault was caused by compression and probably originated from tectonic movements related to the uplift of the Alps West The current structure of the Jurassic Coast has not been altered much since this event Melville Another major geologic feature along the Jurassic Coast where the chalk can be seen is Lulworth Cove.

Here the Lower and parts of the Middle Chalk make up the resistant back wall to the bay Burnsden Lulworth Cove was formed when a stream first breached the resistant Portland Limestone Brunsden This allowed sea water to wash back into the stream and consequentially the weaker Wealdon Beds located behind the Portland Limestone began to erode Brunsden As the Wealdon Beds were eroded more and more the area began to take on the shape of a cove until it finally reached the more resistant chalk beds which greatly slowed the spread of the cove to the north Brunsden The chalk found at Lulworth Cove has been greatly altered by tectonic activity.

The chalk was deposited in the Lulworth Cove area 90 million years ago Gallois However, 30 million years ago the entire area was compressed due to Alpine Earth Movements Gallois and now parts of the chalk have been completely overturned West The chalk can be seen along the Jurassic Coast at the site of the great unconformity which can be viewed at Branscombe and Golden Cap Brunsden The unconformity represents a time gap between rock ages, implying there was deposition of rocks, and then erosion so a great portion of the geologic record is lost.

The chalk is very hard in this spot, and much more splintery than at Old Harry Rocks. It is closer in composition to the Beer Stone which is located below the chalk. In this spot the Triassic rocks are very soft, red, and eroded. The fault has weakened the rocks joining the two beds and consequentially there is a large V in the land between the chalk and Triassic rocks Davies- Vollum 3 Aug The landscape in Southern England has been largely dominated by the chalk.

The Isle of Purbeck is considered to be an island because of the chalk. The chalk has created a hard band of hills that can only be crossed in two locations, by Corfe Castle and on Highway A Davies- Vollum 28 Jul This makes the Isle of Purbeck an island because it is as isolated as an island. Corfe Castle was strategically places in one of the dips that was naturally cut by a river. This means that anyone wanting to go into the Isle of Purbeck had to pass by Corfe Castle so it was an excellent place for trade and consequentially dictation of the surrounding area Davies- Vollum 29 Jul The chalk is also responsible for the topography of Lulworth Cove, because its hard structure does not allow the cove to expand farther to the north Gallois In addition to the topography, the chalk is responsible for some of the vegetation of the region.

Because it breaks down to form such poor soil only short turf can grow there, and hardly any trees Melville