  In models with large extra dimensions, particle collisions with
center-of-mass energy larger than the fundamental gravitational scale can
generate nonperturbative gravitational objects. Since cosmic rays have been
observed with energies above $10^{8}$ TeV, gravitational effects in the TeV
energy range can, in principle, be observed by ultrahigh energy cosmic ray
detectors. We consider the interaction of ultrahigh energy neutrinos in the
atmosphere and compare extensive air showers from TeV black hole formation and
fragmentation with standard model processes. Departures from the standard model
predictions arise in the interaction cross sections and in the multiplicity of
secondary particles. Large theoretical uncertainties in the black hole cross
section weaken attempts to constrain TeV gravity based solely on differences
between predicted and observed event rates. The large multiplicity of
secondaries in black hole fragmentation enhances the detectability of TeV
gravity effects. We simulate TeV black hole air showers using PYTHIA and AIRES,
and find that black hole-induced air showers are quite distinct from standard
model air showers. However, the limited amount of information registered by
realistic detectors together with large air shower fluctuations limit in
practice the ability to distinguish TeV gravity events from standard model
events in a shower by shower case. We discuss possible strategies to optimize
the detectability of black hole events and propose a few unique signatures that
may allow future high statistics detectors to separate black hole from standard
model events.
