A Trip to Chislehurst Caves

Examining a flint nodule at Chislehurst caves

When I first visited Chislehurst Caves as a child, although I can't remember a single thing about it, I am sure that - like family outings to the old Geology Museum and a primary school trip to Sayers Croft – it must have helped to spark off a lifelong passion for geology.

An exploration of The Weald at Sayers Croft in 1969

Nearly 50 years later, during a rare trip to London for pleasure, I took advantage of a weekend stay in West Wickham, at the end of a busy year spent investigating the mediaeval churches in and around South Yorkshire, to visit them again.

Directions to Chislehurst Caves at the bus stop

Setting off on the bus on a Sunday morning, with the intention of getting there before the first tour of the day, I alighted to discover that there weren't any brown tourist signs to direct me to the caves and, once I consulted Google Map on my phone to get my bearings, I finally arrived just too late; however, the hour to the next tour soon passed by as I investigated some salvaged architectural details, some glacial erratics and familiarised myself with my surroundings.

Architectural details and glacial erratics

Apart from trips to the North and South Downs and occasional trips to the Kent and Sussex coast during other family outings as a child, I hadn't seen many examples of the Chalk in the landscape, nor had I any opportunities to study it since obtaining a degree in geology.

A geological map of the area around Chislehurst Caves

Looking at the BGS Geology of Britain Viewer, I have since discovered that post glacial erosion by streams during the Quaternary Period had cut down through the overlying Tertiary rocks to reveal an inlier of the Seaford Chalk Formation.

A map of the passageways at Chislehurst Caves

From the 13th century to the 19th century a labyrinth of passages had been cut into this outcrop, in search of both chalk and the flint nodules that it contains, but the advent of the railways provided access to other expanses of the Chalk in the region – which were subsequently extensively quarried - and it became uneconomic to mine.

An array of lanterns at Chislehurst Caves

Once our group had assembled, we were provided with lanterns and instructions that no artificial lighting was permitted – flash photography, torches and mobile phones – because of the blinding effects that this would have in the darkness. Knowing in advance that the tour focussed on its history, with various tales and legends thrown in for good measure, I was just content to hang back far from the group and discreetly take a few quick snaps of the geology, before catching up with them again.

Various passageways at Chislehurst Caves

Given my very limited knowledge of the geology of the Chalk, I would appreciate an opportunity to be guided around the passages by a geologist but, nevertheless, on this occasion I was just quite content to be underground to marvel at the strata that I could see.

Chalk

Where the opportunity presented itself in a discreet location, I looked for loose pieces of rock in the expanses of the passage walls, to no avail, but I did manage to collect a lump of chalk, as well as a piece of flint embedded in sandstone – from the Thanet Formation that overlies the chalk – which now form valuable additions to my small rock collection.

Flint embedded in sandstone from the Thanet Formation