Good News!

Well they finally recognised the Bridge Drill after it had its photo plastered across the front of 'Geology' in November 2002 (Vol 30 No 11).

The paper generated by the cruise is available in the previous month's edition Vol 30 No 10, where Chris Macleod, Xavier Escartin et al discuss the implications of the recovered core.

BRIDGE Drill PDF (302kB)

The BRIDGE drill is intended to obtain oriented core from exposed seabed rock formations, penetrating, at most, some 1000mm into the seabed. The main client or customer base was the British Mid-Ocean Ridge Experiment (BRIDGE) community, who wanted to confirm directly that the basalt rocks beneath the well established magnetic reversals found across the mid-ocean ridges were caused by rocks on the seabed with reversed magnetic polarity. These rocks were believed to have solidified from molten lava during periods when the North pole was based in the Southern hemisphere, this date could be verified by radio-dating methods and the actual magnetic orientation within the rock could be verified using the inscribed line on the length of the core.

Initially the drill had been the brainchild of Jack Pheasant, who, following discussions with IODP scientists, Chris Macleod and Simon Allerton, realised that their desire for a spatially oriented rock core was now technically possible. He had no solution to the myriad of problems we would encounter but felt that technology could meet the challenge. As it happened he was right. Unfortunately he was unable to do any more than set a team out to design and build the device, before his leukemia caused his untimely death.

August 1997; the drill was placed on the Research Vessel James Clark Ross (JCR) and despatched South for their season supplying the Antarctic bases and surveying the Southern Oceans.

April 1998; the British Geological survey (BGS) team arrived at L'Isle de la Réunion in the Indian Ocean to meet up with the JCR on her way home. They had with them a camera system, devised during the winter months to fit onto the drill and when the JCR docked, they joined the vessel.

After sailing South for 3 days we arrived at the Atlantis Bank (in the Indian Ocean!) where it was hoped that the 'baby' drill could possibly get some 2 days of trials time. The 'main event' on this cruise was meant to be the BGS 5 metre rock drill which would drill out sites obtained during the previous month's reconnaissance by the Canadian ROPOS underwater vehicle.

As it turned out, the little drill had about 4 hours of trials before it became obvious that, in spite of some teething problems, it was quite capable of functioning pretty much as designed. It took 14 days to break enough of the drill beyond which we had no spares for repairs. Meantime it had obtained 13 oriented cores.

April 2001: A further trip in the Atlantic Ocean at the Kane Fracture Zone at 15° 40' North (JCR again) gave another 60 cores or so and proved that the initial results could be followed by a cruise where the drill was now the 'main event'. This cruise also demonstrtated that operation was possible in water depths to 4600 metres, although no core was obtained at that depth as the seabed there consisted of a fine glass sand. The deepest recovery to date has been from 3900 metres.

A website relating a part of the work on drilling mid-ocean ridge basalt materials: RRS James Clark Ross "A Week at the Dentists"