  Large surface detectors might be sensitive not only with respect to extensive
air showers induced by ultra high energy neutrinos but also to showers induced
by hypothetical objects like microscopic black-holes. Microscopic black-holes
might be produced in high energy particle collisions with the center of mass
energies above the fundamental scale of gravity. These black-holes would decay
rapidly by Hawking radiation into characteristic high multiplicity states of
Standard Model particles and induce extensive air showers potentially
detectable by a large surface neutrino detector. In this paper we study the
possibility to detect microscopic black-holes exemplifying it in case of the
surface detector of the Pierre Auger Observatory. The expected event rate is
calculated for up-going and down-going showers induced by microscopic
black-holes. Our calculations show a significant deviation of the expected rate
compared to the rate expected by Standard Model predictions. The rates of
up-going neutrinos are almost completely suppressed, whereas the rate of
down-going neutrinos increase by a factor of about 50 with respect to standard
model calculations. The non observation of up-going neutrinos by the Pierre
Auger Observatory in conjunction with a high rate of down-going
neutrino-induced showers, would be a strong indication of physics beyond the
Standard Model.
