Because the way that they stand and are
Some of the most populous ones are the Guarani, Tikuna, makuxi. The majority of the tribes were assimilated in 2019-2010. The country is going through a fight in the courts with president Bolsonaro on the legitimacy of some of the smaller tribes, and the land they own.
Answer: earthquakes
Explanation: I had the same question and that was the answer
A fan-shaped deposit <em>(of sediment</em><em>)</em> at the mouth of some rivers is called b) an alluvial fan.
A <em>dune</em> is a mound of sand shaped by wind.
A <em>delta</em> is a sort of "tree" of splitting rivers at the mouth of a river.