Contour lines are your friends
There are many types of maps- forest service maps, BLM and highway maps to name a few. Some show general features and points of interest. Satellite maps and aerial photos give a look from above but none show as much information as a topographic map.
In the US, topographic maps are produced by the US Geological Survey (USGS) and are available in digital form for free. All you have to do is download them from- https://www.usgs.gov/core-science-systems/ngp/tnm-delivery/topographic-maps. The downloads of newer maps have topographic lines superimposed on aerial photos - very useful. These can be opened using a PDF viewer such as Adobe Acrobat or similar programs.
But there’s a problem. Topographic maps have so much information that they overwhelm most users who then give up. The most important features of a topographic map are the contour lines and they are your friends. Contour lines alert you to every curve in a ridge or wash, dangerous cliffs and gentle slopes. When you start using topographic maps, I suggest you ignore everything but the brown squiggly contour lines that cover most of the map. These lines will tell you everything you need to know about the shape of the ground you plan to hike or 4-wheel.
Contour lines mark the same elevation around mountains and ridges. Imagine a very smart rabbit going around a hill. He doesn’t go up or down but stays at the same level. If you traced his route, that would be a contour line. Contour lines are drawn at different elevations, usually in 20 or 40- foot increments. They never cross. If the lines are close together, the terrain is steep; if far apart, the terrain is flat. As a contour line crosses a wash, it makes a “V” shape that points up-hill. When it crosses a ridge, it usually makes a “U” shape with the rounded part pointing downhill. A cone shaped hill looks like a bull’s eye. A saddle between two hills looks like an hour glass.
I used topographic maps during my days with Search & Rescue to anticipate where a lost person would be found. If there was an overdue vehicle in the Hualapais Mountains during winter months and there was snow on the ground, I’d look for places where Flag Mine road went over a ridge from a south facing slope to a north facing slope. The south facing slope would’ve had less snow but when the vehicle crossed the ridge, it would’ve hit deeper snow on the north facing slope and gotten stuck. This worked several times and I’d look like a genius. In reality, it was just knowing how to use a map along with wilderness common sense.
The rest of the information on topo maps includes cultural features such as roads, trails, corrals, windmills, cattle tanks and old mines. On the USGS site there’s a guide to all the symbols used. And there’s a bunch. I don’t remember all of them but I’m always amused when I find the symbol for a spring on a map. It looks like a lost sperm to me.
Green means vegetation and blue represents water. Brown spots are sand, a good place to look for someone overdue from an outing in the Standard Wash area near Lake Havasu City, AZ. Riders always seem to underestimate how much gas a motorcycle or ATV uses going through deep sand. A great place for a gas station would be the confluence of Mohave and Standard washes where many searches were conducted for out of gas wheelers.
While working as a geologist, I even used contour lines to map geologic features. A sharp turn in a wash is a good indication of a resistant dike or rock formation. A long straight wash could indicate a fault that had formed a weak zone that was easily eroded. Sometimes I’d combine geologic features with vegetation. In southern Arizona, the Spanish dagger yucca loves siliceous (quartz rich) formations and hates limestone. I’d map geologic formations while sitting on a hill noticing where certain plants grew and how straight a wash was. If only I could’ve trained a dog to tell the difference between rocks by sniffing, I would have been a happy geologist.
To become a good outdoorsperson, you should use maps to anticipate the terrain; to know where you are, to know what you’ll encounter on your hike or ride and to stay safe by avoiding cliffs and other dangerous sites. Also, it makes the outing more fun by looking for springs that might be near old Native American sites or the location of old mines to explore. On historic topo maps, available on the USGS site, they also have old mule pack-train trails and cabins for history buffs. All this information is available on topographic maps for those willing to put in the effort to learn how to read them.
