located in the heart of the Mendip Plateau, on the western side
of the North Hill pericline. North-west of the village is North Hill.
At 305 m, it is one of the highest points on Mendip and is formed
from the more resistant sandstone of the Portishead Formation.
Map of Priddy cave systems (click to enlarge view).
Aerial view of Priddy (click to enlarge view).
The younger Avon Group mudstone forms a belt of damp marshy ground
around the hill, often marked by a shallow valley.
Much of Priddy village is on the Black Rock Limestone, which dips
gently to the south at about 25°. Although there are very few
exposures, the rocks can be seen in many of the dry stone walls.
To the east of North Hill is an area of a Dolomitic Conglomerate
and Mercia Mudstone which infills a deep Triassic wadi. Good examples
of the red breccia and conglomerates can be seen in the dry-stone
walls around Stockhill Forest.
Several major cave systems occur
around North Hill, formed where water draining off the sandstone
sinks underground on reaching the surrounding limestone. Swildon's
Hole is the longest cave on Mendip, with over 9 km of passage. First
descended in 1901, it is also one of the earliest systematically
explored caves in Britain. Cavers can follow the stream through several
water-filled sections to a point 170 m directly below the Queen Victoria
Inn on Priddy Green. Two other smaller swallet caves occur nearby.
Eastwater Swallet is located at the end of a classic small blind
valley, while St Cuthbert's Swallet is the second longest cave on
Mendip at nearly 7 km, and certainly the most complex. The water
from all three caves reappears at Wookey Hole. Several other smaller
caves exist in the area, particularly around the Hunter's Lodge Inn.
Many large sinkholes occur in Stockhill Forest where the ground
has subsided into dissolution cavities in the limestone-rich conglomerate.
The Priddy area was an important lead mining area from Roman times
right up to the beginning of the 20th century. The ore, principally galena,
was won from veins in the Triassic Dolomitic Conglomerate in what
is now Stockhill Forest. Numerous closed depressions pock-mark the
area and the remains of the lead workings with spoil heaps, pits,
leats and reservoirs are still clearly visible in the valley between
North Hill and Stockhill Forest. The area lay between two mining
ownerships known as 'liberties'.
The St Cuthbert's Leadworks operated
by the Bishop of Bath and Wells lies at the southern end of the valley.
Farther north the Chewton
Mineries, owned by the Waldegrave Family was located near Waldegrave
In 1860, the owners of Wookey Hole Paper Mill, concerned about pollution
of their water supply, traced the water from St Cuthbert's Swallet
to Wookey Hole using 'Vanadium Red' dye, having first had several
unsuccessful attempts using chaff and even ink. This provided the
basis for a successful lawsuit in 1863 against the St Cuthbert's
Leadworks for polluting the stream. This has since been confirmed
by more recent dye tracing, the water flowing to Wookey Hole in about eight hours.
The St Cuthbert's and Chewton Mineries are now a Nature Reserve,
known as 'Priddy Mineries', managed by the Somerset Wildlife Trust.
The site has a variety of distinctive habitats including valley mire,
open water and wetland habitats, and lead-rich spoil heaps, and the site
supports a very wide range of flora and fauna. In particular, valley
mire is a very uncommon habitat in the Mendip Hills and here it is
especially important for its rich wetland flora, supporting good
populations of all three British newts, many different species of
dragonfly, as well as frogs and toads.
The spoil heaps are high in lead and other heavy metals, and this
generally deters vegetation growth. The rare alpine penny-cress and
spring sandwort thrive on lead-rich soil, and the loose black slag
is stabilised by rafts of mosses and lichens, including very rare
moss Ditrichum plumbicola.