Thanks for the brief article about topo-map reading [Outdoor skills, January/February 2016], which is rapidly becoming a lost art in these days of GPS smart phones. A couple of things to add:
Indeed, in theory you could encounter a forty-foot cliff that is not on the map. In practice, I encounter much higher cliffs (eighty to a hundred feet) that are not on the map. Night travelers should be especially alert to this. In addition to the contour intervals, map users should be aware that the maps are based on aerial “spot” data, and not all areas are field checked. So if a cliff is “between the spots,” it may not be represented on the map.
Also, the general advice that “V’s indicate valleys and U’s indicate ridges” is applicable here in our worn-down, rounded old mountains. But it should be noted that in younger ranges, which often feature sharp arêtes and rounded glacial valleys, the opposite may be true.
Tom DuBois, Glens Falls