Quebec Blackout Storm

What happened

A severe geomagnetic storm triggered by two coronal mass ejections — one from an X4.5 flare on March 10, 1989, the other from an M7.3 flare on March 12 — collapsed the Hydro-Québec power grid within about 90 seconds, leaving six million people without electricity for nine hours. It remains the archetypal case study for geomagnetic hazards to power infrastructure.