Portland's main caves are under land protected by planning or buildings so threatened primarily by over-use, or abuse,. Being dry, hydrological problems are unlikely. Some formations have been "collected". Quarrying has "found" and destroyed many shorter caves. Conservation measures must rely on education of cavers, including "adventure" centre clients; and planning controls perhaps reinforced by SSSI notification.


Heavy use of a few relatively easy and easily accessible caves has taken its toll. Only these caves are described here.

The Grove Cliff rift (mass-movement) caves deteriorated very rapidly after they were linked in 1986. The system comprises Skittle Alley, Flagpole and Guano Rifts, and phreatic Allotment Dig: 4 entrances. Floors were already trampled, but walls became muddied, obscuring the limestone and its chert inclusions - and spoiling an interesting traverse (poetic justice?). Once-notable moonmilk has been ruined by clumsy chimneying, graffiti-scratching or ignorant handling. A swinging boulder in Guano Rift, left stable by the diggers, was demolished for a youth group on spurious safety grounds. Allegedly, a fairly easy squeeze was needlessly enlarged after a girl "got stuck".

Allotment Dig, originally silt-filled, presently carries a digging railway. That was installed without damaging the cave, but with hindsight, the sediment should have been better recorded. The exhumed limestone surface was soft, and local children carve names in it. They (the names) are scraped away occasionally. An artificial entrance squeeze between concreted boulders may be suitable protection.

More positively, the main local users, including a LEA outdoor education centre, do try to look after the cave. Carbide residue (and acetylene soot stains!) are unknown, and the little litter found is probably left by local children.

Fossil Cave is in a disused quarry used as a massive fly-tip. Representations have been made to the Planning Department when necessary, to request continued access to the cave should the quarry be filled in. Its outer reaches are littered by adventurous children; worse, vulnerable formations in its constricted inner parts have been damaged and muddied by cavers squeezing by.

Blacknor Hole / Sandy Hole is Portland's most important system. The nature of the entrances mean it ought not be an "adventure" cave, but it does attract some odd visitors.

Blacknor Hole is fairly clean in its main routes, and has fragile formations which are deteriorating: a set of distinctive chocolate brown stalactites has disappeared. Fine stream sediments precisely cut by the later mass-movement rifts opening across the ancient conduits, were trampled away soon after discovery in 1976.

Lower-level Sandy Hole is very muddy, and we fear that mud will be dragged into the upper cave, spoiling its white limestone walls as well as the formations.

Recent extensions to Sandy Hole have some fine formations and unusual deposits. Tape, and he nature of the cave, may protect them. A trip to the far reaches now involves several hours of low crawling on muddy, angular boulders. Nowhere can you stand up.


Ironically, quarries "discovered" many of Portland's caves. With little or no recent contact between caver and quarry-owner, the two interests have largely coexisted on a "blind-eye" basis. Consequently some beautifully decorated caves have been recorded and left to their fate: it is extremely unlikely they could have been saved.

The finest contained long lemon-yellow straws above a dry 8ft deep gour in yellow calcite. Fortunately the rift ran beyond the quarry boundary, and back-filling over the entrance was a kindness. About 6 of us local cavers were privileged to see "The Jewellery Shop" - being relieved the cave rests once more in peace reflects on cavers as a whole. Perhaps the gour will refill...


By planning policy, disused quarries cannot be used for any but inert waste-tipping, to prevent leachates travelling through the limestone's unusually-open joints. Sharbutt's Rift, the vertical top entrance to Sandy Hole, sometimes stinks of urine from non-cavers using the old quarry in which it opens. The sea-caves at Portland Bill collect flotsam and jetsam, but little can be done about this. Easier caves collect wax from children's candles: this is removable.

There have been instances of human excreta left in cave entrances, blamed rightly or not on climbers.


The caves are regarded as "open", and most are served by branches from regular footpaths.

Blacknor Hole. There is presently no access to the main, Ariel Passage, entrance. In 2002, the cliff top owners (two neighbours) removed the belays and banned climbing on a length of Westcliff extending beyond their boundaries. Among other concerns, a lawyer had “advised” them that they are liable for cavers’ and climbers’ safety! Despite appeals from various quarters, the dispute remained unresolved in late 2004, partly because unrelated, far more serious, difficulties arose for the owners. Up-hill through-trips would be insensitive: regard the Ariel entrance as a rescue-only exit. Frequent traffic from Sandy Hole will drag mud onto the severe linking climb and traverse, and into the upper, clean, series.

Past difficulties between quarry managers and cavers included calls for access controls. These were rejected as impracticable, but practical concerns such as inconsiderately- sited abseil stakes, were addressed by local cavers.

Most importantly, the nearest cavers' car-parks / changing areas are in residential areas, so please drive, park and change considerately.

Please observe seasonal access restrictions to certain areas, to protect the nesting birds. The details are published in the climbing press and leaflets obtainable from local climbing-equipment shops and Tourist Information Centres.


The very few bats, and birds roosting in rift entrances, tolerate us, perhaps due to the caves proximity to roads and houses. Caving is no threat to the rich flora and, mainly invertebrate, fauna in and around the entrances. St. George's Rift, on an SSSI boundary, was covered by backfilling, unwittingly killing its resident bats. Some of the abandoned stone mines of Purbeck (East Dorset) are gated bat reserves.


Most damage in Portland's caves stems from ignorance not wilful vandalism, despite occasional thefts of formations. Adventure group’s clients pay to go caving, rather than to view caves, and supervising large groups of young novices in narrow rifts is very difficult.

Gating most Portland caves is administratively and physically impracticable.

We must appreciate caves for themselves, rather than just as dark obstacle-courses, but how do we inculcate this in non-specialists? We cannot blame all outdoor centres, some of whom have more respect for caves than the "cavers" who have despoiled parts of, say, Easegill Caverns. Ignorance is reinforced by treating caving as just another "adventure sport". No-one wants unworkable restrictions, but interest in and respect for the caves must be paramount.


The Grove Cliff caves are protected by buildings and a road, and by the cliff SSSI. They may qualify for RIGS status at least, as a network of typical mass-movement rifts.

Fossil Cave needs protecting as a locally-typical remnant of joint controlled phreatic passage initiated by preferential solution of the Roach Bed's profuse aragonite fossils. Formations and some sediments survive. RIGS status may help.

The Blacknor-Sandy Holes system is now over a mile total length (September 1995) - and growing. Its fossil passages, below chert and marl inception horizons, were invaded by later mass-movement rifts. Good formations and interesting sediments exist. It lies in a geological and biological surface SSSI; similar status for the cave may be appropriate, particularly as Portland is one of the very few cavernous areas of Jurassic limestone in Britain and now in part of a World Heritage Site..

The Isle of Portland is now in the E. Devon “Jurassic Coast” World Heritage Site, although whether or not this infers greater protection is a moot point.


I would like to thank Mike Read, a present explorer of Sandy Hole, Dominic Sealy, and Mike Jones of the LEA's Weymouth Outdoor Education Centre, for their comments and help.

Nigel Graham
Sept 04 (Updated from original published in 1995)

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