One afternoon this summer, a line of children and adults could be seen snaking its way along the beach between Herne Bay and Reculver in Kent. Wearing red and yellow helmets, lime green vests and carrying clip boards and rucksacks, they wound their way under the cliffs, stopping every now and again to look up or search around their feet.
Occasionally, they would find what they were looking for, a 50-million-year-old shark's tooth, maybe, or an ancient fossilised shell.
The group of 13, with two guides, were on a family day outing organised by the Natural History Museum in London for school-age children accompanied by adults. Other such outings include "In Search of Dinosaurs" and "Fossil Collecting".
This one took the children to Herne Bay to examine the geological layers of the cliffs. They were also looking for fossils and other evidence of ancient life. In the afternoon they visited the Whitstable Oyster and Fishery Exhibition to learn about modern oysters and other local marine animals.
The families were taken from the museum by coach to Herne Bay. Why there particularly? Because, says group leader Diana Clements, it is here that the rock formations of the Thames Basin, dating back more than 65 million years, can be clearly seen. These layers tell us much about the planet's past life - its changing climate and wildlife.
Take, for example, the layer of clay distinctly visible in these cliffs. Around 50 million years ago, south-east England was much further south than it is now. It was under water and surrounded by mangrove swamps, palms and other tropical fauna. Remains of marine life were fossilised in the silts and mud of the seabed and can be seen as a layer in the cliffs.
At Herne Bay, equipped with helmets, hand lenses and collecting boxes and bags, the party set off to examine the different layers of the cliff, to search for fossils and look at the many forms of sea life. All the members of this group found fossils of ancient shells, and one child a shark's tooth.
They also discussed methods of combating erosion, methods which have been too late to save the old village of Reculver from the sea, or the Roman fort that was near it. More modern dwellings, perilously close to the clay and sand cliffs, are protected by a wall of hard boulders.
The children were zealous collectors, tirelessly combing the cliff base and beach for specimens, old and modern, which they brought back for identification. Their parents were more eager for explanations and knowledge. It was a mark of the tour that the needs of different generations were so well met, with many activities and objects to feel and touch for the children and more academic explanations for the adults.
The past is closer than we think. It still forms part of the fabric of our lives and here, in the form of sharks' teeth, oyster shells and cliff layers, it seemed very near indeed.
The tour costs Pounds 20 for an adult and Pounds 10 for a child including coach, admissions, tuition and field notes.
For more details contact the adult education unit, The Natural History Museum, Cromwell Road, London, SW7 5BD. Tel: 0171 938 9123
Where to rock on
Many museums organise family activities linked to natural history and geology. Dinosaurs are particularly popular.
* Wollaton Hall Natural History Museum, Notts. Once the home of the great naturalist Francis Willoughby, it has an interactive, hands-on exhibition aimed at seven to 11-year-olds. Expect plenty of bones. Tel: 0115 915 3900.
* Dinosaur Farm Museum, Brighstone, the Isle of Wight. In l992 the skeleton of one of the largest dinosaurs in Europe was found here. At the farm, visitors handle real bones. There are also guided fossil hunts. The museum is closed for the winter and will reopen in March. Tel: 01983 740401.
* Liverpool Museum: Missing Links - Alive! An exhibition in which moving models convey the story of human evolution. Exhibits include a fossil site. Until November 3. Tel: 0151 2070001 * Ulster Museum. A new gallery traces the history of Ireland from 10000 BC to 1500 BC. Others include the geology of Ireland, and an exhibition called the Dinosaur Show. Tel: 01232 383001.