EVIDENCE FOR A BLOW-OUT AT THE MONEY PIT©
This is a summary of a brief talk given to attendees to the activities of the Oak Island Tourist Society at Western Shore, Nova Scotia, on August 13, 2005 . It is reproduced for general interest and public comment.
On of the most crucial features in understanding the nature of the underground workings on Oak Island is the documented evidence for a past failure at the bottom of the Money Pit. This evidence was first noted in 1931, but its significance was not realized until 1994.
In 1931 William Chappell and Frederick Blair penetrated the Money Pit, extending the greatest depth previously reached from 113 feet to 155 feet. They went where no man had gone before – at least since 1795, when signs of underground workings on the island were first discovered. In the process of removing the shaft infilling they encountered certain artifacts which included an anchor fluke at 116 feet, an axe head at 123 feet and a pick and miner’s oil lamp at 127 feet.
Rupert Furneaux in his well-known book Money Pit – The Mystery of Oak Island (1972) writes “these discoveries perplexed Blair”, he also reports him verbatim in the following words:-
What has this to do with the Money Pit? Quite a lot, because rock bursts at great depth in hard, brittle rocks have their counterparts at shallower depth, when they are called ‘blow outs’. In fact a ‘rock burst’ may be thought of as a more specific type of ‘blow out’. A blow out may be described in general terms as a ‘catastrophic event when the external hydrostatic or rock pressure causes a failure of the rock cavity in which mining is taking place – the mine workings become suddenly inundated with water or rock debris (or both) when implosion takes place – loss of life may result’. Blair’s description tallies exactly with what an experienced underground engineer, familiar with the phenomena of rock bursts and blow outs, would recognise instantly. Blair stumbled on the evidence, but regrettably he failed to recognise its significance.
Blair writes “At about 150 ft. we commenced to uncover broken-up pieces of stone, the nature of which no person here can identify.” These fragments of rock became larger and more numerous with depth until “the bottom of the Pit is covered”. It is a great pity Blair made no attempt to identify the type of rock they had encountered. Since none of those involved in the excavation could identify the rock, it may be presumed that none of the workers had seen it before either at higher levels in the shaft or at surface. Everyone present must be assumed to have been familiar with granite, slate, basalt and limestone, as these rocks outcrop in the general area, or are constituent members of the ubiquitous glacial till which otherwise blankets the region. The only rock type which is present at depth, but not evident at surface, is gypsum/anhydrite which is now known to directly underlie the Money Pit. When Blair and Chappell were engaged on their excavation they would have had no knowledge of the presence of this material at greater depth, for it is only from deep boreholes put down in the 1960s that the first real evidence arose regarding the existence of this quite treacherous rock type in the immediate vicinity.
Anhydrite, or calcium sulphate (CaSO4) is a weak, water soluble rock which can hydrate to its allied form gypsum (CaSO4.2H2O), by absorbing water in accordance with the following chemical equation, which is fully reversible:
CaSO4 + 2H2O = CaSO4.2H2O
(anhydrite) (water) (gypsum)
The process of hydration from anhydrite to gypsum results in considerable volume expansion and, conversely, dehydration results in volume shrinkage. This expansion process, when it occurs, creates an extensive pattern of shear fractures within the altered anhydrite. This shear fracturing constitutes systemic weaknesses prone to subsequent solution and enlargement by flowing water, particularly where sea water is involved. Because of the chemistry of the solution mechanism gypsum/anhydrite is more soluble in salt water than in fresh.
As soon as any excavation within the gypsum/anhydrite became exposed to water, all anhydrite in the immediate vicinity would have converted more fully to gypsum, with general weakening as a consequence of associated volume expansion. As rock strength decreased, the ability of the rock to sustain stress would have diminished, and once that ability dropped towards a threshold value the likelihood of a catastrophic event occurring would have become greater. A blow out at the base of a shaft would lead to a plume of rock debris surging upwards, possibly triggered by pumping or bailing operations. In the process of rising upwards the larger, heavier fragments of rock debris would have lagged behind the smaller, lighter materials, and a degree of segregation would have resulted much in the manner described by Blair.
Les MacPhie has provided borehole evidence showing the anhydrite/gypsum contact at the base of the Money Pit shaft is lower than elsewhere in the general proximity. It may be concluded, therefore, that the violence of the blow out event was sufficient to pluck out the rock and, consequently, many of the rock fragments encountered in the shaft (some fifty feet higher) can be attributed to this source.
Blair writes that “Both (the axe and the pick) were in perpendicular position and in soft, disturbed or filled ground ….” From this statement it cannot be ascertained whether the axe and pick either fell from above or ascended from below, as long-handled tools such as these will assume a similar aspect whether they be dropped from above or rise from below. It was assumed by Blair that the tools and associated artifacts found between depths of 116 and 127 feet had fallen, but the possibility remains that they may have originated from depth, being transported upwards within the plume of debris.
An upwards surge of debris within the Money Pit shaft would have risen high enough to counterbalance the hydrostatic pressure imposed by the external sea level. Simple physics shows the column of debris would have ascended to between 115 and 125 feet below ground surface, that is marginally below the point where the invert of the Flood Tunnel connects with the Money Pit shaft at a depth of 114 feet. The question that must be asked is – what came first, the chicken or the egg, i.e. the blow out or the Flood Tunnel? It is too much of a coincidence that the debris column rose to within a few feet of the intersection between shaft and tunnel! It must be concluded, therefore, that the Flood Tunnel was excavated later.
The Money Pit shaft and the Flood Tunnel are two very dissimilar elements of the underground workings on Oak Island. Whereas the shaft could have been dug by anyone (first time around) with little engineering knowledge, the excavation of the tunnel required a higher degree of sophistication and mining experience. They are as different as chalk and cheese, and certain as they are to have been constructed by different parties the likelihood exists that decades elapsed between their separate excavations. The Flood Tunnel is 2½ feet wide by 4 feet high, which is significant in that these were standard dimensions for many British mines, dimensions which had been adopted by the sappers and miners in the British military.
The implications conclude that the Flood Tunnel was constructed after the blow out, and whatever had been at the bottom of the Money Pit had proved irrecoverable. Therefore, that which had been lost must have been of enormous value to permit such an undertaking. The archival evidence points to the lost treasure of Sir William Phips.