Beach

Photo:Pebble from Brighton beach

Pebble from Brighton beach

Photo:Pebble from Brighton beach

Pebble from Brighton beach

Photo:Pebble from Brighton beach

Pebble from Brighton beach

Query: Are the pebbles a natural phenomenon?

These messages were originally posted on the My Brighton and Hove  messageboard . They are reproduced here because the topic is of general interest.

Query
Are the pebbles a natural phenomenon, or were they put there to stop erosion? If so, when, and where did they come from?
Sue Cornish, 30/07/2001

Response 1
Pebbles are moved along the South Coast by longshore drift. This combination of prevailing wind and tidal current moves material from West to East. Whenever there is a cliff fall the chalk gets washed away and the embedded flint, being much harder rolls around the sea floor getting rounded.

Sometimes the flints get trapped in sand or clay for a few thousand years. In this case the pebbles are stained brown on the outside. Pebbles that have been trapped in chalk get stained white. Blue (grey) flints have not been stained at all and are prized by the pottery industry as they can be crushed and used as a glaze. Baskets of these were often collected for sale by poor people in the 19th century. Thus it can be seen that pebble movement can be entirely natural and can protect the coastline from further erosion.

Where man has interfered with the natural processes by building Newhaven Harbour arm or Brighton Marina pebbles have to be transported to depleted beaches (as at Seaford) in order to restore the protection to the coastline.

A very interesting video of the replenishment of Seaford beach can be viewed or obtained from the Martello Tower Museum on Seaford Seafront (open Weds, Sats & Suns).
Tame Ferret, 31/07/2001

Response 2

  1. Natural occurrence
  2. Flint eroded out of chalk cliffs. The soft friable chalk got bashed up by the sea and harder flint remained, and rolled into their circular shapes by the action of the sea and the pebbles grinding against each other.
  3. Certain amount of longshore drift whereby the pebbles moved into a eastward direction by the action of the waves, so the flint may have originated from chalk cliffs in West Sussex.

Tricker questions to answer are how the flint got into the chalk in the first place, and how the chalk is formed. See more information on my web sites:

http://cbr.nc.us.mensa.org/homepages/BMLSS/coastal.htm
http://cbr.nc.us.mensa.org/homepages/BMLSS/LowTide.htm#Longshore drift

Recommended Book: Pebbles on the Beach by Clarence Ellis (Faber) ISBN 0 571 06814 6 pbk. There is also a local booklet by Dr Malcolm Cornwall about pebbles on the beach, probably published by the University of Brighton.
by Andy Horton, 01/08/2001

Response 4
I believe that originally the beaches at Brighton were sandy. I have seen several old prints which show this. According to my history lessons at school in Brighton (some years ago now) much of the sand was removed for use in building (to mix with cement) before there was any regulation of this sort of extraction of natural resources. So although the pebbles are in fact natural, the beach itself has been substantially altered by human action.
by Jon Davies, on 01/08/2001

Response 5
If these pebbles are 'a natural occurrence', why then are they only seen on the beach section and stop when the water begins? If you look from the pier, you will see clean sand - not one pebble in sight! Also, there is not enough current or even wave movement to generate the movement of these pebbles by 'long shore drift'. If this does happen, then surely we would see many pebbles in the ocean and not clean sand. I agree with the comments made by Jon Davies.
by Cassandra Garmston, 02/06/2003

This page was added on 22/03/2006.
Comments about this page

When I was a kid in the 40s and 50s, where the Marina now stands was the start of the Undercliff Walk. The beaches east of the Black Rock swimming pool were covered by pebbles averaging six inches in diameter. Why were they much larger than on the beaches westwards?

By Mick Peirson (15/11/2006)

It's not as painful to have sand in your nick nicks than it is to have pebbles!!!

By Jo Bartholomew (21/08/2007)

I can remember when I was a child, Brighton beach always had a lot of tar on the pebbles. My Mother used to rub the tar on our skin with butter and then it washed off easily. Can anyone else remember doing this?

By Sandra Waite (01/08/2008)

I just did a walking tour of Southern England and spent 2 days walking along the beach from Brighton to Bognor Regis and the pebbles are exactly the same all the way along. There is no way that could be man made! I also watched the waves at one part where the water got deep very quickly so the waves broke right over the pebbles and I noticed every single time the pebbles would be pushed up off the sand creating the layer of pebbles on top, separate from the sand. It is certainly a natural landscape and not caused by man.

By Jonas Ashton (26/04/2009)

The tar on the beach was the reason we as kids did not wear good clothes for the beach, you often didn't notice the tar until you got home.

By Joyce Blackman (16/01/2010)

The sea is a fantastic and conniving force both strong and immense. I lived by the sea until I was 21, in Eastbourne and saw what the sea can do. In winter, if there was a particularly rough sea, it would empty many beaches of pebbles and sand, right down to either the hard pack sand or the baserock. The ramps going down to the beaches would have their foundations exposed, also the promenade foundations too, it was a great time to go beach hunting as well. Then the next day all the pebbles returned as if nothing had happened. Sometimes the sea would wash tons of pebbles up onto the lower promenade and council workers had to shovel them by hand out of the shelters and back onto the beach. It is definitely a natural occurrence, the sea is able to sort out different size pebbles and very often you will get a mixture of coarse sand and small pebbles at the half tide mark. Councils spend thousands of pounds installing groynes and repairing them to stem the flow of pebbles easterly which should prove the fact that the sea moves them and could deposit pebbles in an obstructive way in just one area if left to its own devices. That is how Pevensey Levels were formed, by the longshore drift of pebbles east to west. Pevensey marshes were originally under water until the flow of pebbles cut the sea off when the penisula extended all the way to Bexhill. 1066 and all that.

By Paul Kerry (14/03/2016)

The pebbles along the Sussex shoreline are 99.9% flint, being part of the chalk that forms the South Downs. During the five ice ages we have had over the past two million years the Downs were covered in deep snow for thousands of years; there is no evidence of glaciation further south than North London. During the short Arctic summers the snow field's surface would melt and the meltwaters, unable to sink into the underlying deeply frozen chalk, poured over the land surface packed with frost shattered razor sharp flints, sands, gravels and clays. This poured south and north off the chalk. That to the south eventually was covered by the rising waters of the melted snows and about 10,000 years ago the Channel formed. The flints are rolled by the currents and are rounded into pebbles, pushed ashore by wave action and moved generally west-east by longshore drift; very little actually comes from cliff falls. This is a non-renewable resource that is being relentlessly dredged offshore for industry and will eventually deplete our beaches, which is worrying as with global warming, sea levels along the south coast are rising, while we are geologically sinking. Not a good combination!

By Geoffrey Mead (15/03/2016)

The tar which nestled unseen on the shingle until you found you were covered in it was from ships. Back in the day ships were allowed to flush the dregs of their empty fuel tanks out at sea which clumped together to form tar. Nowadays ships are not allowed to clean their tanks at sea any more, they must be cleaned in an enviromentally friendly way, usually at a harbour by a professional company.

By Michael Brittain (17/03/2016)

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