The Nova Iguaçu Volcano ("Vulcão de Nova Iguaçu" in Portuguese) is located in the state of Rio de Janeiro, Brazil, in an area of volcanic rocks at the north-eastern border of the Mendanha massif. Klein and Vieira proposed the site to be an extinct volcano with a volcanic cone, volcanic crater, and volcanic bomb. Scientific journals have studied the volcanic geology of the area, identifying the rocks of volcanic appearance as constituted of subvolcanic intrusive rock bodies. The Nova Iguaçu volcano theory is now extinct in academic communities, but the myth continues in sightseeing promotion groups. Recent research revealed that volcanic eruptions did occur in the Nova Iguaçu region. After the eruptions, an intense uplifting and consequent regional denudation took place. 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 Municipal Park is underlain by the geologic bodies corresponding to the magma chamber (composed of syenite and trachyte) and subvolcanic conduit (made up of pyroclastic rocks) of a depth of 3 kilometers, such as pyroclastic dikes. That is, no extinct volcano is present at Nova Iguaçu. The outcrops are world-rare geological phenomena that expose the underground geologic structures of the volcanic area.
Locality 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. It is 800 meters long, 700 meters wide, and 180 meters deep at 22°46′1″S 43°27′59″W. This area is surrounded by peaks more than 400 meters high, such as Contenda Rock, Austral Rock, Confeito Rock, and Contento Peak, which are underlain by pyroclastic rock. This rock originated from rock fragments created by a volcanic explosion. The valley is made up of trachyte, another igneous rock with massive texture. The pyroclastic rock was the main justification of the Nova Iguaçu Volcano hypothesis.
Proposal of the volcano hypothesis The existence of a volcano at Nova Iguaçu was proposed by geologists Viktor Carvalho Klein and André Calixto Vieira in the 1980s. Klein and Vieira based their discovery on the presence of pyroclastic rocks (including volcanic bombs) and the existence of a volcanic crater. They believed the pyroclastic rock to be pyroclastic flow deposits, constituting an “extraordinary well-preserved complete volcanic edifice”. The bread-crust bomb was highlighted as further evidence. The work of Klein and Vieira led to a doctoral degree and a pamphlet-style geological field excursion guide. However, their work was not published in scientific journals, and therefore the Nova Iguaçu Volcano hypothesis did not receive the attention and scrutiny necessary to transform it into an academically accepted scientific theory.
Later development 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. Some members of the group agreed with Vieira that a volcanic crater existed at Nova Iguaçu (Loc. 1). However, other members disagreed because the supposed crater is underlain by massive trachyte, not volcanic breccia.
Public awareness 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 were placed in strategic locations around the area and included on the DRM-RJ homepage. Brazilian media began publicizing the hypothesis of a volcano at Nova Iguaçu based on interviews with a geologist who stated it was the only area in Brazil with clear morphology of a volcanic crater and a volcanic cone. In 2004, the Nova Iguaçu Topshopping held the Volcano Exposition, and the Rio de Janeiro State Financial Tribunary declared the volcanic crater to be a natural sightseeing attraction point of Nova Iguaçu and Mesquita. The Nova Iguaçu Municipal Government and the Mesquita Municipal Government helped to distribute the information. These non-academic sources had a special interest in the volcanic crater, commenting that an extremely long eruption lasting from 72 million years ago until 40 million years ago was incompatible with the scientific study of Earth’s volcanoes. In early 2005, numerous media, governmental, and scientific sources reported that mining activity of the Vigné Quarry (Loc. 7) was destroying Brazil's only intact volcano. A judicial process was sent to the Public Ministry of the State of Rio de Janeiro, requiring the immediate interdiction of the quarry. The last report confirmed a volcanic edifice but denied the volcanic crater, recommending reopening mining on a reduced scale. The Nova Iguaçu Volcano theory expanded to become a social phenomenon. Sightseeing, commercial, artistic, administrative, and educational activities took place, as if the hypothesis was an established scientific theory. The environmental education was a notable regional highlight. The city of Nova Iguaçu adopted traffic signs with volcanic images. A movement began to register the Municipal Park to the UNESCO as “Geopark of the Nova Iguaçu Volcano”. Some scientific events and the homepage of the DRM-RJ referred to the Municipal Park as the Geopark. 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.
Scientific doubts The first scientific article concerning Nova Iguaçu geology was published in 2006. In the article, and at several scientific events, Akihisa Motoki presented a case against the existence of a volcano at Nova Iguaçu, showing that the geology and morphology of Nova Iguaçu are incompatible with the volcanic model. No article defending the volcano hypothesis has been published in a qualified scientific journal.
Geological discussion
… excerpt ends here. Continue reading the full article.
