We can best gain some idea of past time by knowing the agencies at work; and learning how deeply the surface of the land has been denuded, and how much sediment has been deposited.
Iraganaren ideia bat egiteko bide hobea izan dezakegu beste hau, lanean ihardun duten indar eragileak ezagutu eta lurrazalean zein erosio sakonak izan diren eta zenbat sedimentu metatu diren ikustea.