This article is about the quantum event. For the ensuing battle, see Black Mesa Incident.
Unstable resonance reaction
The Resonance Cascade is a cataclysmic quantum event created after the insertion of Xen crystal sample "GG-3883" into the Anti-Mass Spectrometer at Black Mesa by Gordon Freeman, culminating in the Black Mesa Incident.
According to notes from Gordon's desk, every object has a set resonance. When studied, the object will resonate even more, and sometimes even rapidly. If the object resonates too much, it can open dimensional rifts and portals. The Xen crystal sample studied at Black Mesa resonated enough to tear a rift between Xen and Earth.
While seeming to be a contained event, it did in fact have repercussions across the entire planet. The Resonance Cascade was the cause of not only the interdimensional rift, but also all the following events. It sparked Portal Storms across the whole Earth, and ultimately led to the Seven Hour War and the Combine invasion of the planet.
The Resonance Cascade is therefore arguably the single most significant event in the entire Half-Life timeline, being the cause of all the games' events.
 Half-Life and expansions
The Resonance Cascade caused an aggressive rift to form between the Xen borderworld, the Race X world and the Black Mesa complex on Earth in 200-. While at first only basic Xen wildlife, such as Headcrabs and Barnacles seemingly emerged through the rift, other intelligent creatures, such as Vortigaunts, were also sent to the other side by the Nihilanth, leader of the Xen forces.
The cascade was set to continue until stopped manually, and Gordon Freeman, being the one who caused it, took up the job of closing it. Once the rift appeared to have closed on Earth's side after Freeman had launched a satellite rocket into outer space, the remaining scientists from the Lambda Core discovered that the portal was being held open on the other side by the Nihilanth. Freeman then traveled through a portal to Xen to kill the Nihilanth, preventing him from keeping it open any longer, closing it on both sides.
 List of appearances
- Half-Life (First appearance)
- Half-Life: Opposing Force (Mentioned only)
- Half-Life: Blue Shift (Not seen directly)
- Half-Life: Decay (Not seen directly)
|Black Mesa Incident · Particle Storm · Portal Storm · Resonance Cascade · Superportal · Teleportation · Warpball|