The Quake was a massive geological event that occurred on the planet Quesh, beginning around 53,600 BBY. A series of groundquakes that lasted for three hundred years, the Quake caused Quesh's continents to shift several meters apart, creating massive fissures and rifts in the ground. The poisonous chemical venenit queshaaga was released from the planet's depths, saturating the atmosphere as it evaporated and wiping out all of the native fauna as it turned the atmosphere from temperate to toxic.
In comparison, a groundquake 1/100 the power of a tremor during the Quake would wipe out any structures on the surface, though the planet had since that time been geologically stable for thousands of years.
- Star Wars: The Old Republic (First mentioned) (Codex entry)