Maps and Terrain

When planning a long-distance walk, I always study maps to learn the terrain.  Is the trail uphill or down?  Is it rocky or smooth?  Is it boggy or dry?   With knowledge of terrain, an experienced walker can accurately estimate essential elements, like speed of travel and distance between pubs.  A good hiking map not only shows us the location of roads, rivers, and pubs, but depicts the terrain we’ll encounter when we get lost trying to find them.  Terrain varies with location, and is typically the result of millions of years of geological events affecting the Earth’s crust.

Those of us who attended primary school before the launch of sputnik probably learned that the Earth was shaped like a pear.  Even back then, science had come a long way since asserting the Earth was flat, but scientists held to the pear-shaped theory until astronauts returned with actual photographs. 

Scientific theory is often formulated from flimsy evidence, but once a theory is accepted it takes overwhelming evidence for scientists to change their beliefs.  Galileo had difficulty challenging accepted theory that the Earth was the center of the solar system; Einstein never accepted the theory regarding quantum movement of electrons in atoms expounded by Neils Bohr, but most scientists now accept Bohr’s findings.  (I’m no Einstein, but the relativity of quantum theory to a finding of boredom seems obvious.)  But like everything else, scientists eventually evolve.  I can’t tell you how happy I am that physicians have evolved from days when they applied leeches to patients.  I know some lawyers who still believe in bleeding clients, but even they are a minority.

One of the theoretical observations I remember from school is that, for its size, the Earth is smoother than a billiard ball.  In other words, goes the theory, if the most highly polished billiard ball were enlarged to the size of the Earth, all if its minute imperfections would be exposed as canyons deeper and mountains higher than any on Earth.  That might explain why I prefer to hike on Earth rather than on billiard balls.

If you accept the theory, then its converse is also true: if the Earth were shrunk to the size of a billiard ball, it would be smoother than a billiard ball. (It would also be wetter than a billiard ball, but I’ll save that for a future posting.)  My point is that the flat, two dimensional maps we use may actually be more representative of terrain than we realize.  Indeed, if the Earth’s area shown on a map were reduced to the size of the map, most of our mountains would be flat. 

For example, my AAA roadmap of Great Britain has a scale of 1:1,000,000.  Ben Nevis, the tallest mountain in Britain, is approximately 4,400 feet high.  If Britain were shrunk to the size of my map, Ben Nevis would be about 1/20^th of an inch tall.   The ink used to print contour lines on a typical hiking map may be thicker than the contour itself would be if shown to scale on a relief map.

That concept troubles me, because when I was boy, 3-D relief maps were my favorites.  I loved walking my fingers up mountains and floating them down river valleys.  But it was all fantasy.  My teachers told me that the vertical scale on virtually every relief map is greatly exaggerated for effect.  I couldn’t have been more devastated if they had told me that Jayne Mansfield had implants.

So that’s why maps use contour lines – lines can represent elevation changes more accurately than relief maps can.  Not that contour lines are actually necessary.  Every hiker knows that the land drops on the near side of a river and rises on the far side, that rivers flow downhill, and that oceans are always lower than every place else.  (OK, I’ll concede that there are a few places below sea level, like Death Valley or Holland, where you’ll either die from heat stroke or get your finger stuck in a dike, but in those places you have much more to worry about than contour lines.)  You also don’t need contour lines to know that if you walk against a river’s flow, you’ll be walking uphill.  On a map, if you find a place from which rivers flow in every direction, you can be pretty sure that place is a mountain, even without contour lines. 

Geologists tell us that mountains are caused by three things: volcanoes, uplift (which has nothing to do with Jayne Mansfield), and erosion.  While you don’t normally think of erosion as building mountains, rain and wind can make a mountain by tearing down everything nearby.  Sort of like Barack Obama with health care.  Over millions of years geological events like lava from erupting volcanoes, uplift from colliding tectonic plates, and erosion from mighty rivers and long-winded politicians have smoothed the Earth’s surface to create the flat terrain we know today.  Or at least that’s the theory.

(c) 2014 Ken Klug