xkcd.WTF!?

Explanation ➲

This comic is a public service announcement (PSA) telling the reader to stay out of the Pacific Ocean on the current day. The reason for this is explained to be that someone has lost their wedding ring in a subduction zone. This is a boundary where two tectonic plates in the Earth's crust collide, and one plate dives beneath the other into the Earth's mantle. The ring can be seen glimmering on the upper surface of the subducted oceanic plate, in the accretionary wedge below the continental plate. Given that the rate at which this occurs is of a few centimetres per year at most, and assuming that the characters shown are drawn to scale and are of average human stature, it can be estimated that the ring has been in the subduction zone for about 200 years. Possibly this time has been needed to localise it and then deploy the heavy engineering displayed.

As a result, the United States Geological Survey (USGS) is "pulling the plate back up" to retrieve the ring. This would be a ridiculous idea, since no man-made machine is capable of moving entire tectonic plates.^{[citation needed]} Even if it were possible, it is unlikely that the USGS, a national organization, would invest the time and effort required for such an operation for the relatively trivial purpose of retrieving a wedding ring, particularly for people who are presumably long since dead. If they did, though, staying out of the ocean would be a good idea, as it would be liable to cause tsunami over a wide area, as well as other dangers.

The title text jokes that since the wedding ring lies on the lower (oceanic) plate, the oceanic crust and continental crust are "getting married". Of course, most humans wouldn't be able to see the sight of the wedding ring, due to it being underground, and in the mantle, where no human could reach anyway — assuming that it hadn't already been mechanically deformed (crushed, mangled and/or broken apart) by the action of being sandwiched between two continental masses, and eventually melted.