Sequence of STA 171 Å base-ratio images at 18:49, 18:53:30, 18:56, and 18:59 UT, showing the launch of the EUV wave by the horizontal expansion of the CME cavity (which is far more strongly expressed in the southward direction due to the initially nonradial rise of the CME) and the subsequent detachment of the wave front from the cavity. Due to the upward rise of the cavity, its horizontal expansion at heights h ≲ (0.2–0.3)R_⊙ in both northern and southern directions has terminated by the time of the final panel. The wave in the northern direction is much slower, but can be seen clearly in the corresponding animations in the online edition.