ISLE OF PORTLAND
Summary
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.
Overuse
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.
Quarrying
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...
Pollution
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.
Access
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.
Wildlife
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.
Education
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.
Notifications
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.
Acknowledgements
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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