[3][4][5] The Nova Iguaçu volcano theory is now extinct in academic communities, but the myth continues in sightseeing promotion groups.
The cones, craters, lavas, pyroclastic flow deposits, and volcanic bombs have been washed away in the strong tropical erosion of this region, exposing the underlying geologic structure.
The debated volcano is in the Municipality of Nova Iguaçu, about 35 kilometers to the west-northwest of Rio de Janeiro, Brazil.
It is a horseshoe-shaped valley opening to the north at the north-east flank of the Mendanha massif, about 2 kilometers south-southeast of the Nova Iguaçu railway station.
The existence of a volcano at Nova Iguaçu was proposed by geologists Viktor Carvalho Klein and André Calixto Vieira in the 1980s.
In the early-to-mid-2000s (decade), a research group composed of geologists from several Brazilian institutions conducted additional geological studies into the existence of a volcano at Nova Iguaçu.
[11] In 2004, the Rio de Janeiro State Department of Mineral Resources (DRM-RJ) started a public information campaign about the geology of Nova Iguaçu with special attention given to the Municipal Park and the theories concerning the extinct volcano.
As a part of the project, panel-plates with information about the hypothesis of the Nova Iguaçu Volcano[12] were placed in strategic locations around the area and included on the DRM-RJ homepage.
In early 2005, numerous media, governmental, and scientific sources reported that mining activity of the Vigné Quarry (Loc.
[16] A judicial process was sent to the Public Ministry of the State of Rio de Janeiro, requiring the immediate interdiction of the quarry.
Certain newspapers printed, based on the interviews of another geologist, that the UERJ and Petrobrás (Brazilian National Petroleum Company) were investing one million dollars over two years in researching the oilfield by means of the Nova Iguaçu Volcano.
Vieira & Klein presented the north-south geologic cross-section of the supposed crater, showing a prominent volcanic cone.
Vieira & Klein presented an illustration of the Nova Iguaçu volcanic cone, of 1.7 kilometers in diameter, 250 meters in relative height, and 27° in flank angle.
[27] A volcanic bomb is one type of essential fragment originating from a magma drop, launched from the crater in viscous semi-solid state.
In case of high-viscosity magma, such as andesite and dacite, the consolidated clast surface is cracked by the volume expansion originated from vesiculation.
This body has a horizontal extension larger than 15 kilometers and stretches from the base to the top of the Mendanha massif, with more than an 800-meter drop in elevation (Motoki et al., 2007a).
Research has clarified the inexistence of crater, cone, bomb, lava, and pyroclastic flow, and the scientific problems of the previous works were pointed out one by one.