The shoreline is where the sea casts up many treasures, along with less inviting items such as marine waste, plastics, oil and tar balls. Many natural objects can be mistaken for man-made and if you take a walk along a beach with a keen eye it should become clear that there is a lot more to beachcombing than just 'flotsam and jetsam'.
Although many interesting objects originate in the sea, many more, such as pebbles, fossils and semi-precious stones are the result of erosion of the coastline by the sea. Everything on a beach tells a story; interpreting this story can be even more exciting than the discovery.
Why the fascination with beachcombing? Is it the thrill of finding something for free that might serve a useful function if re-cycled or is it the fun of collecting objects for creative purposes? Driftwood sculptures and sea-shore 'art' are frequently found decorating the inside of holiday homes and beach huts, sometimes even finding their way into homes located far from the sea. Whether collected as souvenirs of a glorious day on the beach or as objects of beauty in their own right, these pieces of seashore debris never fail to fascinate.
What are 'flotsam and jetsam'? Strictly speaking flotsam is cargo or wreckage floating on the surface of the sea, whilst jetsam is cargo or waste thrown overboard and washed up on the beach, but usually the two terms are used together to describe anything on a beach that would not naturally be found there.
Although much is ugly waste, occasional objects of beauty may appear. Frosted fragments of glass in jewel-like colours, colourful string and rope, brightly coloured fishing floats, rusted metal and wooden decking frequently find other homes and other uses.
But there is a lot more to beachcombing - beaches are naturally composed of sand, shingle or pebbles. Pebbles on a beach can look so inviting when wet and shiny, as if freshly polished in a tumbling machine. If you take a closer look at the pebbles however, you may be able to match them up with the types of rock exposed in nearby cliffs.
You may find red (desert) sandstone pebbles along the coast of Devon, chalk and flint pebbles along the South coast and smooth, elongated fragments of grey and green slates along parts of the Welsh and Cornish coasts. Hard crystalline rocks give rise to glistening pebbles, close examination of which reveals a complex history: fine-grained, black basaltic pebbles from the Antrim coast and Western Isles of Scotland, the result of volcanic eruptions some 60 million years ago; pink, grey or white granite pebbles of Cornwall, Arran and Aberdeen crystallizing from hot, molten magma deep within the Earth's crust; shiny mica-rich pebbles, sometimes containing rusty red garnets, the result of deep burial and recrystallization of ancient, pre-existing rocks.
Sometimes pebbles on a beach may not resemble those in the nearby cliffs, which poses the question as to where they may have originated. Some may have been carried there by currents and longshore drift from other coastlines; perhaps more interestingly, some may have been deposited there by melting glaciers towards the end of the last ice age. Pebbles of ancient rocks originating in Scandinavia are frequently found on the East and North-East coasts, as soft boulder clay dumped by retreating ice sheets is eroded by modern coastal processes.
Some pebbles and rocks on the beach reveal even more interesting treasures. Along the Northumbrian coast and in Dorset, hard limestone nodules may be cracked open to reveal curly ammonites and other marine fossils.
Instead of fossils, some of these nodules may contain spider-like shrinkage cracks infilled with white, crystalline calcite; known as septarian nodules, these may often be observed in distinct layers in the cliffs, as well as lying around on the beach as a result of coastal erosion.
The soft crumbly cliffs of East Anglia and the Isle of Wight unleash fragments of bone and teeth of ancient sea creatures, dinosaurs and woolly mammoths, and tiny black fossil shark teeth and fossil wood are often washed up along the waterline at Walton-on-the-Naze.
Fossil sea-urchins, sponges and burrows may be preserved in the flints found along the South coast shoreline; although flint itself is an inorganic mineral made of silica, most of this silica is derived from the spiny skeletons of sponges which were common in the chalky seas of the Cretaceous period when most of the flint was formed. Dinosaur footprints and the trunks and roots of fossil forests have also been discovered along the Northumbrian, South Wales and Isle of Wight coastlines.
Semi-precious stones are often highly sought after. Orange-brown fragments of Baltic amber, transported by ice sheets during the last ice age and now washed up along the Norfolk coast are the fossilized remains of resin which oozed out of the trunks of ancient pine trees some 40 million years ago.
Shiny black jet, much prized as mourning jewelry in Victorian times, formed when trunks and branches of the ancient Monkey Puzzle tree were washed down from the land into a stagnant shallow marine basin some 180 million years ago; rare fragments of jet may occasionally be found washed up along the Whitby coast.
Sea coal found along the Northumbrian coast formed even earlier, in a tropical rain forest when, during the Carboniferous geological period, the British Isles were situated much further south than they are at present, close to the equator.
Serpentine, found at The Lizard in Cornwall, was formed when part of an ancient seafloor was thrust upwards onto the land as two ancient continents collided, also during the Carboniferous period.
The remains of modern marine life washed up on the beach may form the fossils of the future. The black 'Mermaids Purse' is the dried, empty egg case of a dogfish or ray; white cuttlefish 'bone' is actually the internal shell of a creature related to the squid; whelk egg cases form a spongy mass resembling expanded polystyrene.
Shells of all shapes and sizes reveal the huge diversity of life that exists just beyond the waterline, living on or above the seabed or buried beneath it. Razor shells are so shaped in order to assist their burrowing lifestyle and mussels develop thin thread-like 'beards' in order to anchor themselves to rocks. Whelks and winkles crawl across the seafloor in search of food, whilst scallops may flap through the shallows in an ungainly dance to escape predators.
The shells of modern sea-creatures such as sea-urchins, crabs, oysters, mussels, cockles and whelks resemble those of more ancient forebears often found fossilized within the associated rocks and pebbles. By observing modern organisms in their natural habitat we are able to interpret the likely environments of deposition of similar, but ancient, fossilized creatures.
We should not forget soft-bodied creatures. Though less likely to be preserved when dead, due to rapid decay of their soft parts, they form a significant population along our coastline. Brightly coloured jellyfish are frequently stranded on the beach by an out-going tide, whilst delicate sea anemones abound in the safer confines of rock pools, their fragile tentacles searching for food in the surrounding waters. Lugworms hide away beneath the surface, the only evidence of their existence being the holes that mark the entrance to their U-shaped burrows and the worm casts thrown up on the shoreline at low tide.
The seashore is also a botanical playground. With its evocative smell, seaweed typifies a rocky shoreline, a seascape giving inspiration to artists and photographers alike. Long flat fronds of brown kelp, with rubbery stalk and root-like holdfast often still attached, are frequently found littering the beach. Branching bladderwrack, with bubbly air pockets that 'pop' when pressed, clings to rocks and floats gracefully in rock pools. Bright green, slimy sea lettuce forms a slippery carpet on wave-cut platforms.
Lichens abound, covering rocks in a myriad of colours, from dark, black spots often mistaken for oil, to bright yellows and oranges, and silvery greys. Black lichen, with its delicately cracked surface and distinctive 'warts', encrusts rocks and shingle all around the coast, often high above the watermark and in the splash zone which few other life forms can tolerate because of the adverse effects of temperature change and water loss.
Although hostile to most, the salty, shifting habitats along the coastline are highly favoured by certain other types of plant: spiky marram grass colonizes wind-blown dunes; sea lavender and pink thrift form soft, bouncy cushions of vegetation along cliff top paths; sea kale and sea bindweed poke up from crevices and cracks in the rocks.