21st August 2018


A trip to take more photographs and have time
to get a good look around and make some observations of my own. It was a
chilled and peaceful time spent in the cave.

There is a change in the sediments that
partially filled the low bedding sections on the approach to the breakthrough
into An Unexpected Development. Initially, the sediments are mostly sandy silt
with occasional cobble and boulder-size fragments of fractured calcite
flowstone. The fractured calcite flowstone becomes more frequent and after the
drop down through the draughting rift becomes the dominant component of the
sediment fill. It was suggested that the damage was caused by earth movements
but, after close examination of the sediments and some documentary research,
this is unlikely, and the cause of the fracturing is through frost and/or ice.

Most of the passage in Hallowe’en Rift is shallow
below the surface and root growth has been noted in several areas, there are
snail shells in the extension to An Unexpected Development and some rare bat

During the Pleistocene, interglacial and warmer interstadial periods produced calcite flowstone deposition in the cave. Glacial or stadial periods caused periglacial activity in the cave, during which the calcite layers were fractured by frost heave and some redistribution by solifluction occurred.

Hallowe’en Rift was shallow enough for ice to
form in the cave during glacial periods. During the build-up of ice and it’s
subsequent thawing, ice can flow and slide, thereby stalactites and curtains
can be sheared off the roof and stalagmites can be tipped over or sheared off
their bases and displaced. Lumps of calcite enclosed in ice can be deposited on
inclined surfaces or be left in precarious positions, i.e. at positions which
would not be stable if deposited by falling.

Ice related damage covers a wide range of phenomena:

· Missing ceiling formations of older

· Sheared-off stalactites and curtains,
deposited on top of floor speleothems;

· Broken and deposited stalagmites;

· Sheared-off stalagmites which have shifted
from their base but still stand upright;

· Cracked conical stalagmites;

· Tilted and leaning stalagmites;

· Moraine-like piles of floor flowstone;

· Precariously placed ceiling deposits.

In addition to speleothem damage, freezing
and cave ice can leave other traces:

Cryoturbation in cave sediments;

Solifluction deposits;

Transport of gravel without evidence of
flowing water;

High collagen content of fossil bones’

Loss of uranium due to ‘leaching’;

Scratch marks on cave walls.

observations and comments

“The polished nature of the dolomitic
conglomerates was noted throughout most of the cave with hard
limestone/dolomitic pebbles and crystalline red marl matrix having been eroded
equally. This erosion pattern is in marked contrast to the dolomitic
conglomerates in Home Close where the softer matrix is eroded preferentially
compared to the limestone pebbles that stick out as knobbly lumps. The
polished erosion pattern is consistent with a base of a streamway or a passage
full of water as opposed to slow dripping of water. As similar polished
conglomerates are clearly seen down the new pitch, as well as in the roofs of
the horizontal passages which are phreatic in shape and have well developed
scalloping, the logical conclusion is that water that initially formed the
pitch was upward flowing. Undoubtedly there has been a limited amount of inflow
from above later in the history of this cave’s development but it is relatively
insignificant in terms of passage dimensions although highly significant for
the development of the formations.

in the roof, An Unexpected Development. Direction of flow is left to right.

The only other passage development of notable
magnitude has been by a group of nutters using explosives.” (Hawkes, 2018)

“From a speleogenesis point of view, possibly
excluding the aven below the Tuck Shop and a few minor modern runnels, the cave
is phreatic in origin. The few scallops that could be found all pointed
outward, and this, coupled with the lack of any inflow passages into the pitch
strongly suggested that the cave had been formed by water rising-up the pitch
under a head of hydrostatic pressure before flowing outwards along the bedding
planes. We considered that the original outlet was along the choked
bedding-plane connection between the platform at the head of the pitch which
emerges in the crawl just before the breakthrough point and then flows out
along the upper series bedding planes. Later, presumably as the water level
dropped, the water flowed out via An Unexpected Development and the various
passages comprising the Lower Series.

Where all this water ultimately derives from
and where it’s going remain a mystery, which is of course exactly how it should
be.” (Price and Taviner)

The enigma of the where the water comes from
has several possible answers; including from fluctuating sea levels and/or from
rising thermal waters.


Nick Hawkes, Duncan Price, Robin Taviner (pers comms)

Joyce Lundberg and Donald A. McFarlane. 2007.
Pleistocene depositional history in a periglacial terrane: A 500 k.y. record
from Kent’s Cavern, Devon, United Kingdom. Geosphere, August 2007, pp 199-219

Stephan Kempe. 2004. Natural Speleothem Damage
in Postojnska Jama (Slovenia), Caused by Glacial Cave Ice? A First Assessment.
Acta Carsologica 33/1, 18. p265-289

Author: mendipgeoarch

Archaeologist, Geologist, Speleologist