  In scenarios with large extra dimensions (LEDs), the fundamental Planck scale
can be low enough that collisions between high-energy particles may produce
microscopic black holes. High-energy cosmic neutrinos can carry energies much
larger than a PeV, opening the door to a higher energy range than Earth-based
colliders. Here, for the first time, we identify a number of unique signatures
of microscopic black holes as they would appear in the next generation of
large-scale neutrino observatories such as IceCube-Gen2 and the Pacific Ocean
Neutrino Explorer. These signatures include new event topologies, energy
distributions, and unusual ratios of hadronic-to-electronic energy deposition,
visible through Cherenkov light echos due to delayed neutron recombination. We
find that the next generation of neutrino telescopes can probe LEDs with a
Planck scale up to 6 TeV, though the identification of unique topologies could
push their reach even further.
