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.
Si e' sempre pensato che fosse stato o un atto divino o forse un lungo, lento cambiamento del clima, ma tutto cambio' nel 1980, in questo affioramento roccioso vicino a Gubbio, dove Walter Alvarez, tentando di capire qual'era la differenza d'eta' tra queste rocce bianche, che racchiudono creature del Cretaceo, e le rocce rosa superiori, che contenevano fossili del Terziario.