Simple model of umbral flashes including SDFs and SSUBs as part of a broader corrugated structure. The panels sequentially illustrate the cyclic state of the chromosphere of the umbra (i.e. time progresses from A to B to C to A and so on) with small arrows indicating a developing flow, large arrows a strong mass flow, and the solid line indicating the surface where the velocity gradient is highest. The dashed black line in (A) and (C) indicates the previous position of the black line as reference. The yellow stars indicate shocks with size proportional to the strength of the shock, the yellow line indicates the absolute maximum height in the atmosphere that still contributes to line formation, and the dashed red line indicates the monochromatic τ = 1 surface for the line minimum of Ca II 8542 Å.