What do scientists discover when the rains wash away some of the topsoil in the southern region of the Amazon basin in the novel, Through the Arc of the Rainforest?

When rains wash away some of the topsoil in the southern region of the Amazon basin, international researchers and scientists “discover” a huge sheet of rock made of plastic. (Mané Pena and other locals have known of its existence for years.) The Matacão becomes a site for worship, a destination for pilgrimages, a theater for the Ringling Brothers, and the location for countless weddings and funerals. It becomes, as the narrator describes it, “a stage for life and death” (102).