Subsidence is a sinking of the ground due to underground material movement. Its causes can include human interference (anthropogenic subsidence) such as removal of water and natural resources such as oil and natural gas from the ground by means of pumping, fracking, or mining. Subsidence can also be caused by naturally occurring events including earthquakes, soil compaction, glacial isostatic adjustment (GIA), erosion, and sinkhole formation. It can happen anywhere in the world and it does happen in Iceland but is rarely a problem for humans due to the fact that Iceland is proactive about where they build and the country is quite sparsely populated.
Iceland is a country that is constantly deforming. Subsidence in this country has a number of causes such as plate spreading, GIA, volcanic, and geothermal processes. GIA is the ongoing movement of land in response to the last ice age. The following explanation from NOAA made it very clear for me so I am quoting it below in the hopes that you will also find it helpful:
Here's how it works: Imagine lying down on a soft mattress and then getting up from the same spot. You see an indentation in the mattress where your body had been, and a puffed-up area around the indentation where the mattress rose. Once you get up, the mattress takes a little time before it relaxes back to its original shape.
Even the strongest materials (including the Earth's crust) move, or deform, when enough pressure is applied. So when ice by the megaton settled on parts of the Earth for several thousand years, the ice bore down on the land beneath it, and the land rose up beyond the ice's perimeter—just like the mattress did when you lay down on and then got up off of it.
GIA is the main source of vertical deformation in Iceland while plate spreading is the main source of horizontal deformation.
Iceland has long made use of the geothermal waters in this country so an anthropogenic cause of deformation in Iceland occurs around the Reykjanes, Svartsengi, Hellisheidi geothermal power plants as well.
A photo of an “ice cauldron” at Bárðarbunga caldera, which scientists have surmised have probably formed due to volcanic, or geothermal activity below the surface.
As far as mitigation measures are concerned, the Icelandic Meteorological Office constantly shares updates with the public. The government also uses seismic monitoring, satellites, and GPS systems to monitor the degree of subsidence. In addition, as I stated earlier in this post, the country is selective about development and is not a very populous country which also helps in this regard.
Finally, I would like to share this relatively new bit of land in Iceland.(see photo below) This piece of land is temporary as it has already experienced a great deal of subsidence, but I found it very interesting.
Above is a picture of Surtsey Island, which was created in a 1960 volcanic eruption. It is located on the southern coast of Iceland. Already the island has shrunk to half of its original size due to subsidence and erosion. Scientists predict that it will sink back below the surface sometime after the end of the current century.
Sources:
Researchgate
Visit Iceland
https://www.visiticeland.com/article/unesco-world-heritage
NOAA
https://oceanservice.noaa.gov/
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