2638: Bog Hole (Boghole)
Riaño 30T 452045 4800635 (Datum: ETRS89. Accuracy code: G) Altitude 238m
Length 205m + grade 1 extensions Depth 15m
Area position

Updated 10th October 2007; 16th January 2010; 3rd January 2018

   Known as the "The Boghole". A small, slab-covered shaft drops 7.5m to a steep, slippery slope into a chamber with a number of passages radiating. The first two on the left quickly join in a lowering crawl to a dig, while the next one up a short slope is a narrow rift to a choke. The final passage is reached via a 1.5m climb up to a tall rift which leads quickly to a choice of routes. The top level - Up Above Passage - can be followed for 60m of walking and stooping to a final short crawl at roof level to a choke on shattered joints.
   The lower level - Down Below Passage - starts as a hands-and-knees crawl but quickly slopes down to a larger section just beyond a short, tight inlet on the right. Walking, traversing and scrambling over collapsed boulders leads to final traverse over holes in the floor beside a calcite run down the left wall to end at a small "chamber" formed by breakdown after about 100m. An upper route ends at a dig in boulders after 4m, whilst a floor level route goes a similar distance to a choke of sand and shingle.
Both passages follow exactly the same joint determined route, with several overtight holes linking then through the floor / roof, which for much of the length is unbroken.
Both upper and lower levels end at the choke on shattered joints.
   There may be digging possibilites at the base of the entrance pitch. (Communicated by HL)

Reference: anon., 2007b (Easter logbook); anon., 2007d (summer logbook); Corrin Juan, 2007a (survey)
Entrance pictures : yes
Underground pictures : yes
Video :
Detailed Survey : Easter 2007: 1:500 pdf    Summer 2007: 1:500 pdf
On Paul Fretwell's latest version of the Fours Valleys survey
Line Survey :
On area survey :
Survex file : yes (Amended magnetic declination December 2013 to align with Eur79 grid and coordinates altered to fit ETRS89 datum, April 2014.)