This article analyses the textbook published 1991 "Challenge of the Natural Environment", written by Brian Knapp, Simon Ross and Duncan McCrae, adopting the water cycle as a dynamic background for the flows and interactions between the Earth spheres. The water cycle helps students to understand the difference between the subject matter and the investigation of Geology, a distinction which is fundamental for the teaching of Earth Sciences. Such approach helps to understand the way Geology has evolved as a science. The object of investigation is the crust, where a great diversity of structures, rock compositions, fabrics and textures exist. The subject matter is the historical-geological process reconstructed from naturally "fixed" forms. The step-by-step approach goes from the simplest to the most comprehensive concepts; it highlights the risks caused by: (a) an incomplete knowledge of natural processes or (b) absence of concern for effects of human activities on nature.
Water cycle; Epistemology of Geology; Textbooks; Teaching of Earth Sciences
