Where is chalk forming today

You think, wow, it was literally here. Building on techniques pioneered by Smith in the early 19th century, modern surveyors use fossils and microfossils to identify layers of chalk. Back in , Farrant told me, police called on the help of local geologists when a tiny fragment of chalk was found underneath the wheel arch of the Soham murderer Ian Huntley. Two particular microfossils were discovered in the chalk: one found only in the Seaford and one only in the upper Newhaven.

The presence of both microfossils meant that the chalk fragment could only have come from a specific 2-metre thick layer — and the only place that chalk could have been driven over was a local farm track that a farmer had covered with that specific chalk, and where Huntley claimed he had never been. The chalk fragment formed part of the evidence that eventually secured his conviction. A t the top of the Beacon we sat down. It was very still and very silent. Somewhere up above a skylark was calling.

From here you could see the fields of Buckinghamshire, Bedfordshire, Hertfordshire and Oxfordshire beyond. In the distance a row of small bushes flamed yellow and red, a line of fire along the edge of the green field.

It made sense, I was thinking, that the first people to live here headed for this place, climbed up the hill to where a view of the world opened out.

Graham ate a banana and said that tomorrow she wanted to try to collect sloes. He got out a laptop and began to enter data. The map they were working on is funded by the Environmental Agency and two major water companies. Because chalk is highly permeable, it acts as a huge aquifer, providing a source of drinking water. The chalk also acts as a natural filter, purifying the water that drains through it. But there are also fractures in the rock — and here the water flows instead of drains.

Water companies need to know how the water flows through the chalk, where it can be safely extracted. And for that they need an accurate, detailed map of the different formations. The Holywell fractures in a different way from the Seaford.

A crack in the Newhaven is not the same as one in the Zig Zag. The next chapter of the story of the formation of the Chilterns took place around , years ago, when immense ice sheets covered the north of Britain, reaching down as far as Watford. Beyond the ice, the Chilterns was a wild expanse of cold, empty tundra. Unable to permeate the frozen ground, melting water flowed over the surface of the land, forming river channels that eventually cut down into the rock to create the dry valleys that are such a distinctive feature of the chalk landscape.

Further north, everything was just bulldozed by the ice. I pictured great blocks of ice moving remorselessly across a landscape — ice heavy enough to grind and smooth away the very rocks in its path. A few weeks after my trip to the Chilterns, I went for a walk on the North Downs, on the other side of London.

Following a farm track towards the ridgeway, the buzz and roar of the M25 was faint but insistent, like the distant rush of the ocean. Underfoot the path was pale brown and, where the thin topsoil had blown away, bright white — the bones of the land exposed.

Reaching the ridge, I paused, turned and saw London in the distance. Grey and silver towers coming up out of a muzzy blueness away over the beech trees and red-tiled suburban roofs. As I stood there, looking back towards the city, it seemed as though the blueness intensified. And then it looked for a while as though the old Cretaceous ocean had returned to the London basin.

Or as though I was seeing a flooded city some time in the future. I thought about melting ice sheets and sea level rise and how, as I stood there, the south-east of the island was sinking while Scotland rose up — a see-saw effect caused when the great northern ice sheets began to melt around 20, years ago.

The majority of Chalk reservoirs are redeposited allochthonous beds. These include debris flows and turbidite flows. Porosities can be very high when preserved from diagenesis by early hydrocarbon charge. However, when these hydrocarbons are produced, diagenesis and compaction can re-start which has led to several metres of subsidence at seabed, the collapse of a number of wells, and some extremely expensive remedial work to lift the platforms and re-position them.

Category : Sedimentary rocks. Read what you need to know about our industry portal chemeurope. My watch list my. My watch list My saved searches My saved topics My newsletter Register free of charge. Keep logged in. Cookies deactivated.

To use all functions of this page, please activate cookies in your browser. Login Register. Additional recommended knowledge. Topics A-Z. All topics. 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. Follow us on:. Written and designed by Roy Shepherd.

Special thanks to my wonderful wife Lucinda Shepherd, friend Robert Randell and various experts for their support. What is chalk? Right: A giant chalk ammonite exposed on the foreshore at Peacehaven. Chalk is one of the best known of rocks, recognisable for its white colouration in striking land features such as the White Cliffs of Dover and Seven Sisters pictured above , and familiar to most in everyday products such as blackboard chalk.

Chalk has been exploited by man for thousands of years for both its physical and chemical properties and has fascinated scientists for centuries because of the fossils it contains and the geological story it tells.

How did the Chalk form? Chalk is formed from lime mud, which accumulates on the sea floor in the right conditions. This is then transformed into rock by geological processes: as more sediment builds up on top, and as the sea floor subsides, the lime mud is subjected to heat and pressure which removes the water and compacts the sediment into rock.

If chalk is subject to further heat and pressure it becomes marble. The lime mud is formed from the microscopic skeletons of plankton, which rain down on the sea floor from the sunlit waters above. The Coccolithophores are the most important group of chalk forming plankton. Each miniscule individual has a spherical skeleton called a cocosphere, formed from a number of calcareous discs called coccoliths. After death, most coccospheres and coccoliths collapse into their constituent parts.

Most chalks formed during the Cretaceous period, between and 60 million years ago, and chalks of this age can be found around the world. The Cretaceous chalks record a period when global temperatures and sea levels were exceptionally high. This coincided with the break up of the supercontinent Pangea, which broke apart to form the continents of today. As continents move apart, an ocean forms between them, and new ocean-floor is added along the line of spreading known as the mid-ocean ridge by magma which rises from below.

As the continents moved apart in the Cretaceous, a very high volume of magma rose up to form the new ocean-floor in what is known as a superplume event.