Without touching the classical sources (such as the territories of ancient populations, Moesia and Thrace were well known to classical writers, as evidence, p. Eg., The fact that the Rhodope has already mentioned by Homer, The., XIV, 227), it can be said that even for Bulgaria the beginning of an exploration conducted with modern criteria does not go back beyond the second twenty-five years of the last century, when the religious struggles fought by the Bulgarians particularly recalled the attention of European scholars on the southern region of the lower Danube. A. Griesebach (1839), A. Boué (1840), M. Blanqui (1841), J. Müller (1844), Grigorovič (1848) mark the starting point of our not only geographical but scientific knowledge of Bulgaria in a broad sense; knowledge to which, in the second half of the same century, mainly German scholars contributed. Among the many, of this or another nationality, who traveled the region and illustrated it under various aspects, AM Perrot (1855), VA Papadopoulos (1856), A. Viquesnel (1857-69), F. Kanitz (1860-80), JG von Hahn (1861), G. Leean (1867), and L. Hugonnet (1886). But only after the liberation from the Turkish yoke did the exploration become truly intense and, as the times allowed, systematically scientific. From this closer period, the names of F. Toula, H. Kiepert, C. Sax, A. Tuma, R. Oestreich, A. Burchardt, and, among the Slavs, K. Jireček, the ingenious historian, are remembered with honor. of Bulgaria, KG Popov, J. Ivanov, GM Zlatarski, L. Dimitrov, L. Vankov, J. Cvijić, A. Iširkov, of which the latter two have particular merits in the field of geography. Overall, and especially from this point of view, if the country can be said to be quite well known, it must be recognized that regional studies are still in their infancy, also because the historical events to which it has been subject in the last fifty. For Bulgaria 2001, please check naturegnosis.com.
The Balkans and Rodopes offer wide scope for intensive reconnaissance, not only as regards the morphology, still imperfectly known, but also in the studies on the population. The Bulgarian Military Geographical Institute has published several maps of the kingdom: one at 40,000 (200 sheets until 1926) and one at 50,000 (27 sheets); a third, on a scale of 1: 126,000 (63 sheets), embraces a larger part of the Balkan peninsula. Bulgaria is also included in the well-known map at 200.000 of the Military Geographical Institute of Vienna, and in the international one at the million, in which it occupies sheets NK 34-5 of the provisional English edition.
Geology. – The Balkans separate two zones with distinctly distinct characters: the wide band of Cretaceous assizes that expands to the North., parallel to the course of the Danube, and the even larger mass of land that continues at noon the characteristic agnotozoic formations of the peninsula, stretches from the middle Danube to the Cyclades. Rodope, Pirin, Rila, Strandža, central and eastern Balkans are made of gneiss, limestone and crystalline schists, crossed by eruptive expansions that correspond in several places to the highest elevations. Of the Paleozoic horizons only the Carbonic is well represented: in NW Bulgaria. emerges in sandstone beds alternating with clayey and anthracitiferous schists, characterized by facies continental of the Kulm type. The Permic appears in the western Balkans (Iskăr) and in the Sofia basin with characteristic red sandstones and conglomerates, on which the Mesozoic assizes rest, which are also revealed in the middle part of the chain. Overall, however, the extent of the latter is rather modest before the Cretaceous period. During the Trias the size of the continental nucleus of which Bulgaria was part is reduced, until in the Cenomanian the great marine transgression spreads here too, covering all of northern Bulgaria. The Cretaceous period is therefore widely represented, with compact limestone, schistose or clayey, marl, sandstone, etc., which extend from Timok to Mt Nero, forming, in the area close to the Danube, the base of the powerful blanket of löss, which covered them.
The end of the Mesozoic is characterized by intense eruptive activity, of which large traces remain in southern Bulgaria (from Burgaz to Nova Zagora, to S. dello Strandža and in the Sofia basin). The Eocene appears with typical nummulitic limestone formations near Varna, rests on both sides of the Balkans and widens in Dobruja; the Oligocene especially near Burgaz, also with a rather limited extension, as is generally the case in the Mesozoic. Oligocene and Miocene are marked by the orogenetic phenomena that determined the lifting of the Balkans, the sinking of the Danubian plateau and the formation of the tectonic grooves that were to separate this (upper valley of the Tungia [Tundža]) from the more resistant crystalline nucleus, already fragmented in the epoch pre-eocene (basin of the Marizza). The Paleocene shows considerable breadth only beyond the borders of SE. of Bulgaria; a strip is between Haskovo and Nova Zagora, some fragments between Arda and Marizza. The Upper Miocene crops out near Plevna (Pleven) and between Varna and Burgaz, the Sarmatian also in the area facing the Danube, and in Dobruja, between Varna and Silistra. The more recent Tertiary sees to the O. and to the SW. the formation of more or less extensive lake basins, in which the Pliocene depositions take on importance (lignitiferous beds of Pernik and Radomir, middle Marizza basin, Sofia basin, Lom, etc.). Even more than the floods lying on the bottom of the tectonic furrows or along the course of the rivers, we must remember the löss, which covers, as mentioned, large surfaces in northern Bulgaria. Glacial traces (circuses, lakes) preserve the Rodope,
