Luckily for Brazil, it is in the middle of the South African plate and not on the edges of any tectonic plates. This means that they do not have many volcanoes there at all (http://www.invivo.fiocruz.br/ cgi/cgilua.exe/sys/start.htm?UserActiveTemplate=english &infoid= 1275&sid=43). Although they do have some. On the Brazilian island, Trindade, there is a volcano which classifies as dormant (https://www.volcanodiscovery.com/trindade.html). A dormant volcano is a volcano that has not erupted in the past 10,000 years, but is still expected to erupt again. There are no active or even dormant volcanoes on mainland Brazil, but there are two extinct volcanoes in the mainland. There is the Nova Igua รง u Volcano and the Pico do Cabugi Volcano, both in the mainland and extinct (https://en.wikipedia.org/wiki/List_of_volcanoes_in_Brazil). An extinct volcano is a volcano that no one expects to ever erupt again. I could not find anything on what Brazil is doing to warn people when a volcano...
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Brazil is classified as a medium hazard level, which means that there is only a 10 percent chance that Brazil will experience a potentially damaging earthquake in the next 50 years (http://thinkhazard.org/en/report/37-brazil/EQ). Earthquake risks are relatively low in Brazil compared to many other South American countries, but low and medium intensity hazards occur at a certain frequency in Brazil. On November 5, 2015, the Fundao tailings dam of Brazil collapsed due to a series of earthquakes with the magnitude of 2.01 to 2.55, which caused the worst environmental disaster in Brazilian history. In Brazil on average, magnitude 3 earthquakes occur twice a month, magnitude 4 earthquakes occur twice a year, and magnitude 5 earthquakes occur once every 50 years (https://phys.org/news/2017-08-seismic-hazards-brazil.html). Since Brazil does not really experience "big" earthquakes, they do not have to worry too much. In 2015, the dam that fell was just fragile and was not built for ...
Brazil lies on the South American plate, which classifies as a major tectonic plate (http://kangbrazil.blogspot.com/2015/06/plate-tectonics-in-brazil.html). A major tectonic plate contains part of a continent, in this case South America, and part of an ocean basin. Brazil's plate boundaries are divergent, which means that the tectonic plates move away from each other.