So I’m taking an Intro to GIS course and one of my homework exercises involves mapping the original trans-Atlantic telegraph cable.
I remembered that this cable (and I assume all others like it) crosses the Mid-Atlantic Ridge, which I recall from high school science class is an area of seafloor spreading, and it got me thinking: Are large-scale infrastructure projects such as cables, pipelines, highways, railways, and the like, which may cross areas of plate tectonic movement, designed and built in a way that has to account for the expansion or contraction of that area over time?
I know that geological movements are extremely slow, like less than a centimeter per year, still I’m imagining that over the course of many years it may be enough to matter. Thanks in advance!
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Most long infrastructure systems like cables, pipes, bridges, railways, etc. have to have a certain amount of slack, although not for tectonic movement. Materials expand at different rates when heated. So your highway bridge becomes longer then what it spans when hot and shorter when it is cold. You can actually see these expansion slots in the bridges when driving over them allowing for some movement. Similarly pipelines and cables have corners in them where there does not have to be one so that it can bend a bit extra there when heated. Railroads are some of the most difficult things to get right as it needs to be solidly fixed to the ground so it does not move when hundreds of tons of train moves over it or else the train will derail, meanwhile the rail needs to move to account for the expanding steel during hot summers. So these infrastructures can handle the tiny amount of tectonic plate shifting.
It is rare that you have infrastructure right over a fault line, especially one which moves fast enough to pose a problem. For example there is some infrastructure in Iceland which crosses the mid-atlantic ridge fault lines but it is moving so slowly not to pose any issues. However in California there are some rapidly moving fault lines. The primary method of handling this is to not build anything right on top of the fault lines. But there are some larger structures which have gaps in them to allow for ground shifting over the next century.
Yes, but not necessarily in the way you think
Large buildings may have to account for plate tectonics for reasons like Earthquake protection.
In terms of the transatlantic cables you mentioned, yes the spreading sea floor would eventually become a problem, but the cables have adequate slack and they are replaced more frequently that it would be a problem.
Long distance pipes and cables have extra slack built into their design to allow for movement, shrinkage and enlargement.
Example: https://www.industrytap.com/wp-content/uploads/2020/09/industry-2632179_1280.jpg If these pipes were completely straight, they would break if they moved too much since they wouldn’t have slack in them.
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