[In geology,] As in history, the material in hand remains....

“ [In geology,] As in history, the material in hand remains silent if no questions are asked. The nature of these questions depends on the 'school' to which the geologist belongs and on the objectivity of his investigations. Hans Cloos called this way of interrogation 'the dialogue with the earth,' 'das Gesprach mit der Erde. ”

R.W. van Bemmelen