All along it was thought to be either an act of God or perhaps long, slow climate change, and that really changed in 1980, in this rocky outcrop near Gubbio, where Walter Alvarez, trying to figure out what was the time difference between these white rocks, which held creatures of the Cretaceous period, and the pink rocks above, which held Tertiary fossils.
Pensou-se que seria um ato de Deus ou talvez uma alteração climática longa e demorada mas isso mudou em 1980, neste afloramento rochoso perto de Gubbio, onde Walter Alvarez tentou perceber qual era a diferença de idades entre estas rochas brancas que continham criaturas do período Cretáceo e as rochas rosa por cima, que continham fósseis do Terciário.