Matter Effects of Thin Layers: Detecting Oil by Oscillations of Solar Neutrinos

We consider a possibility to use the solar neutrinos for studies of small scale structures of the Earth and for geological research. Effects of thin layers of matter with density contrast on oscillations of Beryllium neutrinos inside the Earth are studied. We find that change of the $^7Be$ neutrino flux can reach 0.1 % for layers with density of oil and size 20 km. Problems of detection are discussed. Hypothetical method would consist of measuring the $^7Be -$ flux by, {\it e.g.}, large deep underwater detector$-$submarine which could change its location.