versão impressa ISSN 0016-7169
In contrast with polygenetic volcanoes, eruptions giving birth to monogenetic volcanoes are much less frequent and thus more difficult to observe and study. Only a few events of this type have occurred worldwide in historical times. Among these, Jorullo (1759~1766), Paricutín (1943~1952), Ukinrek maar (1977), and the East-Izu activity in Japan (1930~1989) are among the events that were studied and reported according to the scientific level of each period. The first two eruptions lasted for several years and were actual births of cinder cones and large lava flows. The maar resulted from a series of phreatomagmatic explosions, with relatively small basaltic magma production, and East-Izu caused earthquake swarms intermittently since 1930 ending with a small submarine eruption in 1989, not large enough to form a scoria cone. Here, we discuss the physical processes that originated those monogenetic volcanoes, mostly from the available seismological data and other reported parameters that reveal similarities and differences among those eruptions. Notwithstanding the common features of monogenetic activity, different types of volcanoes may thus be recognized. The main common feature for all types is a deep seated primary magma source, below the crust. Depending on the ascending capacity of magma derived from the excess pressure at the source and on its buoyancy, the surface activity may range from long-duration, high magma productivity eruptions forming cinder cones and extensive lava fields, to short-duration, low productivity eruptions related to similar sources but with a lower magma ascent capacity, that tends to stall within the crust. End members of the latter type may be limited to phreatic activity related to conducted heat phenomena or to local swarm seismicity. Sharing characteristics of those volcano types, but in a different spatial scale and with a shallower magma source, we recognize another type of monogenetic volcanism, namely the parasitic cones associated to polygenetic volcanoes that seem to result from the balance between the magmatic pressure and the mechanical strength of the polygenetic volcanic edifice.
Palavras-chave : monogenetic volcanism; Jorullo; Paricutín; East-Izu monogenetic volcano group; parasitic cones.