| The development of the stratigraphy brought the renewal of the display method of the geological maps. The First Geological Congress in Paris (1878) put the unification of the stratigraphic classification and nomenclature to the agenda. Finally, the unified color and symbol system of the geological maps was accepted at the Second Geological Congress, held in 1881 in Bologna. The basic theory of the color usage is that the older a formation the darker the hue indicating it. The geo-chronological color distribution used to nowadays was also accepted in Bologna.
The Hungarian geologist József Szabó published three geological maps about the surroundings of the city of Budapest in the second half of the 19th century, in 1858, 1878 and 1887, respectively. These maps have the same extents. In the 1858 map he shows rock types, indicated also by number for the easier identification. For some rocks and for the alluvial units, surface signs are used on white background. In the 1878 and 1887 maps he uses also numbers but the ages of the formations are also appeared. These latter two maps are identical; the only change is in the color system, which is the effect of the Bologna color protocol. |