Evolution of EB event "A" (from Figure 1) in the blue (top) and red (middle) wings of the Hα line profile with the co-spatial SDO/AIA 304 Å filter (bottom). The EB event appears in both wings simultaneously from an apparent footpoint before extending along a constant axis (identified by the black line of length 1200 km) to its peak length. After the fourth frame, it then fades back along the same axis. The initial images of this figure were taken at 17:32:30 UT and each subsequent image 77 s later.