Earthquake swarms don’t always have to bode ill. Often the weeks of shaking in the ground subside without anything bad happening – but not always.
They were recently considered a warning sign for the southwest coast of Iceland: thousands of seismic shocks, moderate in strength, but extremely frequent. Like a crush. Such anomalies are feared on the North Atlantic volcanic island because they can indicate magma rising from the depths and thus perhaps indicate an impending eruption.