A little reflection will explain why, along the rising coast of the western side of South America, no extensive formations with recent or tertiary remains can anywhere be found, though the supply of sediment must for ages have been great, from the enormous degradation of the coast rocks and from the muddy streams entering the sea.
Gogoeta apur batek azalduko digu zergatik ez dagoen Hego Amerikako mendebaleko kostalde irtenean zehar inon ere aurkitzerik oraintsuko edo tertziarioko hondakinik duen formazio hedatsurik, aldi iraganetan sedimentuek ugari izan behar izan zuten arren, hango itsas ertzeko haitzen erosio itzela eta itsasora iristen diren erreka lokaztsuak kontuan izanik.