Subspace fracture

From Memory Alpha, the free Star Trek reference

A subspace fracture is a rip in the space-time continuum. A fracture in subspace can cause temporal anomalies.

Subspace fractures can be formed by the detonation of polaric ion energy. (VOY: "Time and Again")

In an alternate timeline, the USS Voyager encountered a Class M planet devastated by the detonation of polaric ion energy. The explosion resulted in the formation of subspace fractures around the planet's surface. Kathryn Janeway and Tom Paris were caught in one of the fractures and were pulled back in time before the destruction of the planet.