O niektórych szkolnych modelach geologicznych

Abstract

Some models used in school for demonstrating tectonic deformations can be accepted only with certain reservations as to their correctness. Ad an example may be taken a model illustrating the formation of folds, which is composed for instance off strips of stiff cloth; considerable hollows will form in the resulting folds; in reality such hollows are never present. A model for demonstrating dips which is cmoposed of a Boardsoreen with vertical chinks in it and with sections representing the shifting parts of rocks has bolts inserted at the back. These bolts serve a double purpose - that of propping up the shifting parts, and of screwing, these parts to the screen. That model has two serious defects. The first is - that the shifting of sections on the screen is possible only in a vertical direction which gives the wrong impression of forces acting vertically and cousing discontinued tectonic deformations. The other defect of the model is that between the displaced sections big clefts will form which in fact, owing to compensation action between the displaced rock parts, are absent in reality. In teaching practice such defects ought to be explained, and the faulty models ought to be as far as possible corrected.