It is best accessed from Hanbury, with parking in The Cock Inn- see waypoint. There you will find more information about the event, and also a board showing three walks in the local area. The Red Route takes in the crater rim- see Trailhead. It is across fields, often muddy and sometimes containing cows. There are styles to cross and uneven woodland paths.
This Earth Cache has been published at 11:11am on 27th November 2014, exactly 70yrs since the events explained below happened.
The mine was taken over by the RAF in 1937 to use as a munitions store of up to 40,000 tonnes of bombs and explosives. On the morning of 27th November 1944 an armourer found a damaged exploder on a 450kg bomb that was within a pile of similar bombs. It appears that he tried to remove the exploder, but used the wrong equipment. At about 11am, it exploded, setting off its bomb, then the whole pile of bombs, then about 3500 tonnes of high explosives stored in the immediate area of the mine. It was heard 60km.
Well over a million tonnes of rock and soil were blasted into the sky, leaving a crater 250m across. The mine was about 35m below the surface, and the blas hole would have been deeper before the sides slumped in.
Upper Castle Hayes Farm was directly above the explosion; it completely disappeared, along with the six people in it at the time. Many buildings in nearby Hanbury were damaged by flying rocks and some debris landed 10km away. In total, 70 people died in the explosion and its aftermath. It took a year of delicate work to remove the thousands of tonnes of ordnance that were reachable, but it is estimated that 3000 tonnes of unexploded bombs remain within the collapsed mine.
Today
A circular footpath has been created to make the crater rim very accessible, but the 'Keep Out' signs should be adhered to considering the unexploded bombs within! Cars can be parked at the Cock Inn (see waypoint), or other places in Hanbury where you can pick up a footpath (see waypoint). It is a lovely walk over fields, along the edge of woodland then round the South East rim of the crater.
The crater is still just over 250m across, and is about 30m deep. Although now very overgrown with many quite mature trees you can still see broken ground on its floor and some blocks of white gypsum 3m across. The slopes are now much more gentle after many years of rotational landslides in the mudstone. The overall profile resembles that of old meteorite impact craters.
Continuing on the path to make a loop back to Hanbury passes a small concrete blockhouse over an air-shaft into the mine. Any fields that have been recently ploughed reeval numerous small blocks of white gypsum, which would all have originated 20m below the ground and been deposited there by the blast.
Gypsum, alabaster and anhydrite
The Tutbury gypsum is the lower of the two major gypsum horizons within the Mercia Mudstone which lies about 35m below the Newark gypsum, and 75m below the Rhaetic Blue Anchor Formation. Both beds consist of anhydrite at depth.
The original gypsum was deposited by incomplete evaporation of shallow saline waters in bays temporarily cut off from the sea along desert shorelines of Triassic Britain. Conversion of the gypsum to anhydrite occurs when the increased pressures and temperatures of burial cause dehydration during the lithification process, generally at depths of about 400m. Re-conversion from anhydrite back to gypsum requires only the addition of water within the deep weathering process, and generally starts when denudation lowers the surface to within about 100m of the mineral.
Today the gypsum forms a variable and discontinuous bed of mineral lenses that reach up to 6m thick. Though much of the gypsum is soft, featureless and almost chalky in structure, some of it is stronger variety known as alabaster. This is highly valued as an attractive and easily carved ornamental stone. The Fauld material can provide very large blocks and is notably pure and clean, with less of the red streaking that characterises the local Chellaston alabaster. The gypsum dips very gently to the south, and passes under the rise of an escarpment, so that its mudstone cover is up to 90m thick a kms south of the outcrop.
Today, Fauld is Britain's leading source if anhydrite, and produces no gypsum at all. The workings extend more than 6km to the south (well off the map) in a belt 2-4km wide. A few sinkholes developed in fields near Hanbury where weathered mudstone was met in the mine roof beneath a previously unknown gravel-filled buried valley. Except for these, subsidence has not been a big problem at Fauld. As an extra precaution, pillars of in situ gypsum have been left under Hanbury village and beneath some clusters of houses to the south.
The coordinates will take you to the memorial places to commemorate the disaster. It is made from a stone donated by a sister mine in Italy, rather than from stone found here. To claim a 'find' on this Earth Cache you must visit the Fauld Crater and answer the following questions in a message to me via my profile.
a) As you approach the crater from the North East you will walk along a path (see refernce point 1) that has been paved with Gypsum collected from the surrounding area after the blast. How long is the Gypsum path?
b) Describe the gypsum used in the path(colours, texture, patterns, ...)?
c) How is the gypsum that can be seen down in the crater different? (see from View Points 1 and 2 and at the listed coordinates)