As the iron ore is mined from the rock and brought to the surface, the ground gradually sinks. Mining generates vibrations, ground deformations and movements that are monitored and controlled so that any impacts can be dealt with in plenty of time.
Ore is an economic concept. It is the size and quality of the ore that determines if it is worth mining, i.e. whether or not it is worthwhile building tunnels and moving machinery ever deeper into the mountain. However, the shape and location of the ore bodies determine where any ground movement will occur and how communities will be affected.
In Malmberget, there are around twenty ore bodies that run in a south-westerly direction under the town. Mining takes place in around a dozen of these. In Kiruna, there is one huge ore body that runs under the city. Gradually, mining is moving deeper into the mines and the ground above is being affected.