Time Wake

A Time Wake was an anomaly in the time vortex caused by the use of primitive time travel technology. The Sixth Doctor told Peri it was "rather like the wake left behind by a ship at sea". The duo encountered one created by Tasq, a Time Engineer from the planet Bestonas. It connected London in January 1986 to the London of 1720.

Time Wakes "healed themselves" after primitive time travel excursions were halted. Until that time, however, they presented themselves as shimmering blue-white rings. People could step directly into the rings and be transported to wherever the Wake took them. The sign of a Wake closing was a gradual constriction of the circumference of the ring. It was possible for Time Wakes to be lethal, if one attempted to enter at a point where the circumference could not accommodate one's personal size. Tasq, for instance, died because he tried to step into a Time Wake that had closed too far. (DWA: Time Wake)
 * The concept is presented as a proper noun in Time Wake''.