Subterranean Canyons, Underwater Sediment Slides, and Subsea Cable Outages

Most African cables traverse the Congo Canyon as opposed to detouring around it. The canyon is not particular deep, but it is huge in terms of floor coverage. Depth varies from 1400 to 1600 meters. Le Trou Sans Fond canyon off Abidjan drops 2300 meters where the canyon meets the continental shelf. It is perfect recipe for sediment and debris avalanches. 

These canyons were created by strong river currents that carve the ocean bottom and also deposit sediment. Debris and sediment slides can easily crush the older African cables lying at the bottom. In contrast, both Equiano and 2Africa are routed around these danger spots. That increases latency, but reduces outages. Sometimes African ISPs are short sighted in this matter. They take WACS despite the exorbitant costs and high likelihood of extended down time because it is a bit faster. 

An interesting question is how long will WACS be worth operating given the accumulated optical loss from one or two outages each year. The more repairs, the shorter the cable life. 

The first sea floor mapping show the Congo Canyon in 2005. The second in 2013. And the last shows the changes over the same period. 

Maps of the Undersea Congo Canyon

Diagram Illustrating a Turbidity Current


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