Locate the dry gorge that circles around this half-circle-shaped hill. With the stereoscope, view this dry gorge on the left (north) side of the hill:

Question

The question is based on Figure 32-3, a black-and-white stereogram, and color Maps T-20a and T-20b (in the back of the Lab Manual). These maps show the entrenched meanders of the Green River near Canyonlands National Park, Utah. A larger portion of this region is shown in color Map T-7 in the back of the Lab Manual.

Begin by looking at the flat-topped, half-circle-shaped hill about 4 centimeters (1.5 inches) from the bottom of the stereogram.

(a) This dry gorge is approximately 2000 feet (about 600 meters) wide. Viewing the stereogram, approximately how deep does the gorge appear? As a starting point for your estimate, consider if the gorge appears deeper than it is wide, wider than it is deep, or equally deep and wide. (There is no correct answer for this question; base your answer on how things look to you.)
Apparent depth __________ feet

(b) Use the topographic map (Map T-20a) to determine the actual depth of the dry gorge (you can simply count the number of contour lines up the side of the gorge, and then multiply the number of contour lines by the contour interval).
Actual depth __________ feet

(c) Was your estimate in problem 2a far off? If so, why?

Answer 1

(a) Apparent depth 1000-2000 feet
(b) Actual depth about 480 feet
(c) If estimate was off, probably due to vertical exaggeration of stereogram.