The Mid-Atlantic Ridge

Double click on image for a better view

In PK NEWS Issue 46 John has written an interesting piece, 'Money Mistakes and the Birth of Science' which includes a section about the mid-atlantic ridge.

Making soundings across the Atlantic in the mid 1800's was a long and laborious task. The number of soundings made along a track would to a large extent dictate the accuracy and worth of the exercise. In mid-atlantic it took anything up to four hours to get a line to the bottom and back up again and in some cases bottom was not reached............Lieutenant Maury's measurements were taken as the best available and what he called the 'Telegraph Plateau' would have appeared as very good news to the Atlantic Telegraph Company. Unfortunately he and others who followed were quite wrong about the profile of the sea-bed along the track from Valentia on the west coast of Ireland to Newfoundland.

I have been doing some work recently on this subject with very helpful assistance from Global Marine Services who hold uptodate bathymetric surveys for many parts of the world's oceans including the Atlantic.
With their help we have superimposed a recent survey on the 1850's plots of Lieutenant Maury and British navy man Lieutenant Dayman RN in HMS Cyclops .
In the image above it is difficult to see much detail, however the RED line is the 21st century plot which shows some interesting features:

• The very steep transition where the Irish shelf ends.
• The area around 350 nm from the Irish coast which is the zone where it was believed the major fault occurred in the 1858 cable.
• Right in the centre the very pronounced Mid Atlantic Ridge which the two previous surveys of the 1850's had failed to detect.

As we can see from modern bathymetry the route between Valentia and Newfoundland was anything but a 'plateau' and one might imagine that there would have been some serious doubts about the viability of a transatlantic cable in 1857 had they been aware of the Ridge.

The Ridge itself runs for a great distance (North / South) in the Atlantic extending from the arctic as we can see on the map above. Research continues on this topic particularly to look at just how much more was known ( not known) about the Atlantic sea bed and the Mid Atlantic Ridge by the time the next attempts to lay a cable were made in 1865/6.