The geophysical data used in the present study are represented by gravimetric and magnetic data. The gravimetric data available at the International Gravimetric Bureau were filtered through different procedures, among which we mention the moving average, with rectangular windows of different sizes with which we covered the entire studied surface, the polynomial surfaces of different degrees calculated according to the least squares method. Each of these two filtering methods brings us information from different depths, depending on the size of the windows used, respectively, the degree of the polynomials. We used the same filtering procedures in the case of the magnetic data from the archive of the Geological Institute of Romania, which, although they have an uneven degree of density of measurement points due to the different relief, still after applying the filtering procedures they were able to suggest a regional trend. The study area is represented by the Calimani-Gurghiu-Harghita (C-G-H) volcanic mountains, which are located in the western part of the Eastern Carpathians of which they are a part. In the Western part of the East-European Platform there is an oceanic crust that is part of a lithospheric plate that subducted under the Eastern Carpathians. This subduction created the Carpathian flysch and molasse zones (nappes) on the eastern side of the Carpathians. On the western side, the Neogene Volcanism appears, which is predominantly andesitic represented by the C-G-H mountains. Their main petrographic types are andesite, rhyolite and basalt. To the north of this sector, the volcanic mountains continue through two other sectors Bârgău-Rodna-Ţibleş and Oaş-Gutâi. These three sectors of volcanic mountains have different properties from a petrographic point of view.