There are more fertile areas in the Amazon River's flood plain, where the river deposits richer soil brought from the Andes, which only formed 20 million years ago.
(the river deposits richer soil; brought; from the Andes; L:the Amazon River's flood plain) (the Andes; only formed; T:20 million years ago)
the river deposits richer soil the Andes
brought only formed
from the Andes L:the Amazon River's flood plain
T:20 million years ago