The pavement explosion in Pimlico, London on Thursday that narrowly missed a passer-by was believed to be caused by faulty power cables, though this merely explains how it was initiated and not where the energy came from to create a mini mushroom cloud that popped out of the pavement like an actual fucking mushroom.
The source of the explosion was an injection of electrons in an excited state, which then decayed at the opportune moment to dump all of their energy into the power cable, which was unable to handle the surge in current at its weak point. These excited electrons are very similar to radioactive isotopes (like uranium) that decay to release large amounts of energy. Normally, electrons are quite stable – the industrialised world wouldn’t function otherwise – but they can be coaxed into this excited and “suicidal” state by increasing their voltage to several million. The local power grid is then hacked into and the electrons uploaded to it, which travel down wires until they eventually decay and explode.
With the right know-how, anyone with a pack of AA batteries, an internet connection and an uplink to the National Grid could potentially set off one of these explosions anywhere connected to the mains power supply, though the random nature of the decays means it’s difficult for terrorists or loner computer nerds to target specific areas, as it is for any regular people who might want to cause mayhem.