  One of the most fundamental features of a black hole in general relativity is
its event horizon: a boundary from which nothing can escape. There has been a
recent surge of interest in the nature of these event horizons and their local
neighbourhoods. In an attempt to resolve black hole information paradox(es),
and more generally, to better understand the path towards quantum gravity,
"firewalls" have been proposed as an alternative to black hole event horizons.
In this paper, we explore the phenomenological implications of black holes
possessing a surface or "firewall", and predict a potentially detectable
signature of these firewalls in the form of a high energy astrophysical
neutrino flux. We compute the spectrum of this neutrino flux in different
models and show that it is a possible candidate for the source of the PeV
neutrinos recently detected by IceCube. This opens up a new area of research,
bridging the non-perturbative physics of quantum gravity with the observational
black hole and high energy astrophysics.
