Saturday, 12 May 2007
Initial Report: Analysis of a ship-wreck off Loch Avie.
Nicholas K, Krogstad A. "Analysis of a ship-wreck off Loch Avie." Proc Royal Soc 2007; 2 (advance communication ahead of printing).
The discovery and analysis of the site of a wrecked submersible in the littoral waters off the Duchy of Loch Avie are reported. Findings support that a submersible vessel, likely under steam power, suffered a catastrophic boiler failure. The wreck is relatively recent, and the lack of crew remains suggests an autonomous vehicle. Further studies are ongoing regarding the origin of the vessel, and details of its control mechanisms.
No reports currently exist regarding any underwater archæological sites in Caledonian waters. The experience of one author (KN) during the Caledon Hydrographic Survey suggests that, as of January 2007, there were no identifiable wrecks in surveyed areas, and a more-detailed exploration of Loch Avie in conjunction with the study of Nessie the Loch Beastie (1) revealed no wrecks in or around Loch Avie.
Despite ongoing civilian and naval traffic, there are no reports of loss of ships, impediments to navigation, or damage to vessels that may occur during inadvertent collisions with submerged wrecks.
As well, there has been no reported seismic activity in the area that may either expose wrecks previously buried under silt, or produce rogue waves that may be a hazard to ships.
Discovery of the site.
The site was initially discovered by one of the authors (AK) while doing sediment testing on the sea floor. One sample container was retrieved containing several pieces of coal; the Caledonian strata are not known to contain anthracite. The authors returned to the site in the Royal Society's submersible (fig. 1) to ascertain the source of the coal.
Starting at the location the coal was found, a standard search pattern (βουστροφηδόν) was begun, in 10m wide rows. Visibility was estimated at 15m at the surface, and 10m at depth. Measurement of the sub-surface currents were in line with prior observations (2), with a 1 m/sec (0.1 Sievert) current at the bottom. A 2-degree-Centigrade thermocline was present at 12 m depth.
The bottom was at 21 m depth, and fairly uniform across the search pattern. It consisted of the typical sedimentary deposits, without evident rock outcropping or other features. No flora or fauna were identified, save for ubiquitous plankton in suspension.
The first evidence of the wreck site was the finding of a screw-and-shaft mechanism, partially buried in silt. (Fig. 2.) The screw was toroidal, with a 50-cm estimated radius, and appeared to be brass or copper. The survey course then continued east-north-east at 80 degrees, along the visible axis of the debris field.
A field of lump coal was found to the east of the propeller, with an approximate 10 m diameter spread. The coal was visibly similar to the originally-extracted specimen, and consistent with fuel coal used in coal-fired steam plants. (Fig. 3.)
Beyond the coal field came larger debris pieces. Multiple metallic shapes were scattered along the debris field axis, buried in silt to various degrees. No identifiable structures or components were among the pieces. (Fig. 4.) The metal was of uniform make-up, averaging 5 cm thick, and without paint or markings. Edges of the fragments were curled and deformed; where an interior/exterior differentiation was noted on the fragments, the deformity trend was from in- to outside. The pieces ranged from one to 3 m in diameter. Application of the external magnetometer revealed the fragments to be uniformly ferrous.
There was no evidence of oxidation or combustion on any of the visible fragments. A failure of the on-board under-silt sounding apparatus prevented locating any obscured pieces, though the magnetometer did detect signal changes under silt.
The four largest pieces formed an axis of 110 degrees, to the east-south-east, turning right from the initially-seen debris field direction. (Fig. 5.) Absent from this section of the site were any smaller (sub 1 m) items. No encrustation of the debris was noted, and no plant or animal life was noted in the vicinity of the wreck. Gieger counter readings were consistent with background radiation.
Proceeding along the secondary debris field axis, the largest piece of the wreck was found approximately within 10m of the eastern-most portion of the debris. (Fig. 6.) A single metallic object, 15 x 2 x 3 m, with a cylindrical protrusion 1 x 1 x 3 m in the mid-section, was lying on the silt, aligned nearly due east. The eastern end was conical, and partially buried in silt. The western end was severely deformed, again with an in-to-out orientation of damage. The interior of this largest piece was open to the sea, but a combination of metal damage and sediment prevented close inspection. However, certain interior features were noted. A plane of metal consistent with diamond-plate decking was evident, along with several pipes, levers, and gear assemblies. No biologic matter was noted, neither human remains, nor expected sea life. The cylindrical feature on the hull was consistent with a sail and hatch, and was rotated nearly perpendicular to the sea floor.
Taken together, these findings are most likely the remains of a submarine vessel. Based on the forward section, the estimated size would have been 25 x 3 x 2 m, with the hatch just forward of amidships, standing at 1 m above the hull. No diving planes were seen; however, it appears that some portion of the wreck has been covered by silt, probably at the time of initial impact with the sea bed. Based on the presence of coal, and the fragmentary remains of the stern, the craft was likely under coal-fired steam power, and suffered a boiler explosion. Due to the relatively compact east-west dimensions of the debris, the vessel was likely stationary at the time of the engineering catastrophe. When the boiler exploded, the aft end of the vessel ruptured, ejecting the coal stores, and sending the shaft-screw section aft. Due to the lack of apparent impact damage, or deep embedding in silt, the vessel was probably close to the bottom, estimated at 15 m depth. The fast undersea current at the site helps provide some timing on the loss of the craft; significant time had not passed between the wreck and its discovery, as there was not appreciable dune formation on the up-current end of debris. The lack of remains (human or otherwise) with this time frame raises the possibility that the vessel was under autonomous control (3). The data do not support further conclusions regarding the method of operation, or origin, of the craft.
A submarine craft was lost off the southern coast of Loch Avie some time between January and May of the current year, likely closer to the latter. It may have been un-manned, and suffered an unrecoverable hull failure after steam plant explosion while at depth. No evidence exists as to the origin, nature, or type (civil versus military) of the ship. Metallurgical analyses are currently being conducted, and a second expedition to explore the interior of the hull is planned.
(1) Nicholas K et al. Proc Royal Soc 2007; 1.
(2) Krogstad A. Unpublished data 2006.
(3) Bell L et al. The speed of post mortem change to the human skeleton and its taphonomic significance. Forensic Sci Int 1996; 82(2):129-140.