In the 1980s the northeast region of brazil received almost no precipitation for how many years?

3 years

Explanation:

Even there was  a dry year in 1979, the area received almost the normal amount of rain in 1980.

In 1981 however, the year was quite dry, with rainfalls in drop of almost 20%, that began one of the most important drought in the history of Brazil.

In 1982, rainfalls were down by 30% and it got even worse.

In 1983, the rainfalls were down by about 35%, essentially destroying all the agriculture system that had been severely damaged by the two previous years.

In 1984, rain came back a bit higher than its traditional levels, and in 1985, the area was flooded by rain surpassing the average by 60%!

Tectonically stable means that this part of the continent has not moved for billions of years. The rock formation is important understanding the history of Earth since its unmoved and untouched state can provide ideas about how the Earth looked like as seen on the layers of the rock formation.