A bubble nucleates and its wall drives the latent heat that — from inside — looks like a Big Bang. Black holes accumulate substrate past the operating regime. The wall stalls, collapses, and on the way down deposits a moraine: a Grimshaw–Smyth dispersive shock wave with a chirped multi-cycle downstream train, a deep recovery-zone depression at the transcritical crossing z = 1.588, and a harmonic edge at z = −0.25 — past the observer, in our future. The first cycle runs clean: watch the bubble expand into pristine substrate so the structure is unmistakable when the moraine forms during collapse. From cycle two onward the crust profile is read from the 15-knot freeform spline fit to DESI BAO + Jia H0(z) (χ² = 9.68 vs ΛCDM's 845.5 on the same observables).
galactic-data-spline.csv