In what sense is a geologic map a scientific model of the surface geology? Is it fair to say that geologic cross sections in combination with a geologic map constitute a scientific model of the three-dimensional geologic structure? (In formulating your answers, you may want to refer to the discussion of scientific models in Chapter 1.)
Why is it correct to say that “large-scale geologic structures should be represented on small-scale geologic maps”? How big a piece of paper would be required to make a map of the entire U.S. Rocky Mountains at 1:24,000 scale?
The submerged margin of a continent has a thick layer of sediments overlying metamorphic basement rocks. That continental margin collides with another continental mass, and the compressive forces deform it into a fold and thrust belt. During the deformation, which of the following geologic formations would be likely to behave as brittle materials and which as ductile materials: (a) the sedimentary formations in the upper few kilometers; (b) the metamorphic basement rocks at depths of 5 to 15 km; (c) lower crustal rocks at depths below 20 km? In which of these layers would you expect earthquakes?
It was the writer John McPhee who called geologic maps “textbooks on a piece of paper” in his epic narrative about a geologic traverse across North America, Annals of the Former World (p. 378). Can you locate a passage in this textbook that describes a geologic structure and sketch a geologic map consistent with McPhee’s description?
Can you explain the geologic story in Exercise 6 in terms of plate tectonic events? Where in the United States do geologists think this sequence of events has taken place?