  The detection of cosmic neutrinos with energies above 1017 eV got growing
interest during recent years. Possible target materials for in-matter arrays of
~100 km3 size under discussion are water, ice and rock salt. Here we propose to
investigate permafrost as an additional alternative, covering ~20% of Earth
land surface and reaching down to more than 1000 m depth at certain locations.
If sufficiently large attenuation lengths for radio and acoustic signals can be
demonstrated by in-situ measurements, the construction of a large hybrid array
within this material may be possible in the Northern hemisphere. Properties and
problems of a possible location in Siberia are discussed below. Some acoustic
data are compared to laboratory measurements using "artificial" permafrost.
