After graduation, in 1949, Marcian Bleahu joined the Geology Department of the University of Bucharest, where he taught the courses of Structural Geology and of the Geology of the Quaternary. In 1961 he is eliminated from the Department by the communist administration, on political grounds. On April 4, 1990, together with Dolphi Drimer, Marcian Bleahu founded the Ecological University, the first private university in Romania and the only university with an ecological profile. Drimer became the rector of this university and Bleahu was appointed as dean of the Faculty of Natural Sciences (later on named Faculty of Ecology), where he taught Dynamic Geology, Physical Geography of Romania, Geology of Romania, Protection of nature and protected areas. He ended his teaching career in 2001. Between 1949 and 1994, simultaneously with his teaching activity, Bleahu worked as a geologist at the Geological Institute, where he implemented most of his scientific activities. Between 1952 and 1985, he did a long series of research in the Carpathian Mountains, mainly in the
Apuseni Mountains. During all these 33 years of field research, he synthesized and made public the stratigraphy and the structure of the Apuseni Mountains. The papers he published in this field are the first scientific source about the geology of the
Maramureș,
Bihor,
Codru-Moma, and
Metaliferic Mountains; he dedicated to each of them a monography. These research activities had an important impact on synthesis of national interest, such as coal deposits, Paleozoic and
Mesozoic formations, but also from the tectonic point of view, in the general works about the structure of the territory, as well as in the integration of these researches in the wider framework of the study of Triassic paleography in Eastern Europe. Directly, or by coordinating teams of geologists, Bleahu also produced over 50 maps (pages) component of the Geological Map of Romania, on a scale of 1:200.000, for which he also made the state standards in the field. A special chapter of this field activity was the study of karstology, meaning the exploration, the mapping and the research of the caves in the Apuseni Mountains, almost unknown until then: Peștera de la Căput, Peștera Buciumul Sucit,
Peștera Vântului, Peștera Vadu Crișului, Peștera Șura Mare, Peștera din Peretele Dârnini, Peștera Coliboaia, Avenul de sub Pietruța, Peștera Izvorul Tăușoarelor, Peștera-aven ghețarul de sub Zgurăști, Peștera Cetatea Rădesei, Peștera Pojarul Poliței,
Scărișoara Cave, Peștera Huda lui Papară, Vânătările Ponorului, Izbucul de la Cotețul Dobreștilor, Avenul de sub Colții Grindului, Peștera Gaura cu Muscă, Peștera Bolii, Peștera Neagră, Peștera Ghețarul de la Vârtop, Avenul din Piatra Ceții, Peștera Calului, Peștera Bisericuța, Peștera din Dealul Cornului, Peștera Mică de la Vânătare, Peștera Dâlbina, Peștera Corobana lui Gârtău, Peștera V5, Peștera Poarta lui Ionele, Avenul din Șesuri etc. In 1976 he published
Caves from Romania "Peșteri din România", which became one of the first scientific best-sellers in Romania. All these researches, as well as the world scientific trends of the 1960s in the field of plate tectonics catalyses Marcian Bleahu's research activity and he becomes a pioneer in the field of global tectonics not only in Romania, but also with significant contributions in the international scientific community. The results of his studies were synthesized in the book
Global tectonics - Bucharest, 1983, Editura Științifică, (
Tectonica globală), in two volumes, with over 1000 pages. Despite the opposition of the scientific world of that time, which got quickly past any debate over ideas and arrived at the political questioning of the research results (the communist authorities forbade him to leave the country for 6 years, 1978 to 1984), Bleahu managed to thrust his theories, and he was invited in 1974, 1976, and 1978 to teach at the
University of Geneva the first course in Global Tectonics; he also gave conferences in Vienna, Zurich, Freiburg, Basel, Potsdam, etc. Between 1949 and 1952 he was the manager of the geology service for the
Danube–Black Sea Canal. In 1953, he coordinated the geological research for the project of
Bucharest Metro. He was a member of the inter-ministerial commission of analysis for the
1977 Vrancea earthquake. Between 1985 and 1994 he was a member of the team that founded and coordinated the
National Museum of Geology in Bucharest. == Political career ==