  The effect of a CFT shockwave on the entanglement structure of an eternal
black hole in Jackiw-Teitelboim gravity, that is in thermal equilibrium with a
thermal bath, is considered. The shockwave carries energy and entropy into the
black hole and heats the black hole up leading to evaporation and the eventual
recovery of equilibrium. We find an analytical description of the entire
relaxational process within the semiclassical high temperature regime. If the
shockwave is inserted around the Page time then several scenarios are possible
depending on the parameters. The Page time can be delayed or hastened and there
can be more than one transition. The final entropy saddle has a quantum
extremal surface that generically starts inside the horizon but at some later
time moves outside. In general, increased shockwave energy and slow evaporation
rate favour the extremal surface to be inside the horizon. The shockwave also
disrupts the scrambling properties of the black hole. The same analysis is then
applied to a shockwave inserted into the extremal black hole with similar
conclusions.
