### Which trail would certainly you take?

Imagine. You out hill climbing through your friends.

You pull the end your map and also see 2 hiking trails.

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The first route has actually closely-spaced contour lines.

But the second route has actually widely-spaced spaced edge lines.

Which hiking trail would YOU take?

For the slow-and-steady climber, you’d choose the second route because widely-spaced edge lines typical the slope is gradual. However if you choose the very first route, she the form of free climber who scales hills with just a pickaxe. This is due to the fact that when contours room close together, it method that the steep is steeper.

For a quick definition, a contour line join points of same and consistent values. Because that example, contours on an elevation have constant heights that room the very same on every line in a topographic map.

### Are this contour lines mountains or depressions?

When you have actually a closed contour like the one below, this method there is a hill/mountain or depression.

You don’t really understand unless over there is a label on the edge line. In the example below, we’ve added labels and it must be clear that it’s a depression.

And this isn’t just any depression. This is the massive meteor crater that struck Arizona a long time ago.

On some maps, cartographers use teeth clues or hachures because that depressions at craters or volcanoes since it point out the elevation goes increase or down.

READ MORE: A Topographic file of Arizona’s enormous Meteor Crater

### How does mountain Fuji’s edge lines look like?

In this case, closed contour lines suggest a mountain. The beautiful mount Fuji was standing 3,776 meters tall over sea level. In ~ 250-meter spacing, here’s just how the edge lines look:

When you check out Mount Fuji in 3D, you deserve to see that it’s rather steep together the contours are relatively closely spaced together.

So far, we’ve seen instances of two species of close up door contours, yet how do contours look choose in valleys?

### The preeminence of V and U-shaped valleys

Valleys are elongated low-lying depressions usually through a river flowing with it. You know that you looking at a valley bottom once contour lines are V or U-shaped.

Here is an example of a 3D watch of the picturesque Collayomi valley in California:

All rivers circulation downhill from higher to the lower elevations, perpendicular come the contour line over it. As a dominance of thumb, the V-shaped contour is pointing upstream (the the contrary direction indigenous the circulation of a currently or river).

The “V” shape contours suggest streams and drainage. As you deserve to see, the “V” point out uphill come a greater elevation. Generally, girlfriend can connect the apexes of the upward-pointing, “V” shame contour lines to delineate a stream. Further to this, you deserve to estimate a stream gradient by count the number of contours the cross a stream with the edge interval.

The slope is constantly perpendicular to edge lines. The much less separation in between contour lines method a steeper slope and also vice versa. When there space evenly spaced contours, the slope is uniform.

At a present junction, contour lines kind a “M” or “W” shape. This have the right to be interpreted as 2 “V-shaped contours intersecting.

### What about ridges and gullies?

Over time, gullies kind through erosion of to run water on hillsides. A consequence of 2 eroded gullies is a spur in ~ the center on the challenge of a hillside the sticks out. Both gullies and spurs run from ridgelines to valley bottoms.

Gullies (or draws) are characterized by “U” or “V” shaped contour lines through their closed-end pointing towards higher elevation. Top top the other hand, spur contour lines suggest toward lower elevation.

In 2D, these valley landscape features are a little more daunting to see. But it’s an essential to remember just how ridges point downslope and gullies allude upslope.

### Why execute contour lines never ever cross?

It’s unlikely that contours cross, but sometimes they do. Once the terrain is one overhang or cliff, edge lines will certainly cross or touch.

The cliffs in Látrabjarg, Iceland are up come 440 meter tall. Once you generate 100-meter contours, they space very close to converging.

In 3D, you deserve to see how steep this cliffs are. For this reason if this contours go cross, it’s an extremely likely one overhang. Or it can be an error in the program.

If you use your imagination, photo an overhang whereby the terrain hangs outward. This would certainly be a rare exemption when 2 contours that cross.

### How to attract contour currently manually?

You can conveniently generate contour lines with the click the a switch in CAD or GIS software. However what if you want to attract it through hand?

First, you have to pick a contour interval. For example, we’re going to usage a contour interval that 10 meters. So this method that there will be a edge every 10 meters.

Between change points of ten (30, 40, 50, etc), add markers wherein to draw lines. Basically, draw or interpolate between the lines.

Now that we have actually points come connect, let’s draw smooth edge lines because that each interval. Essentially, we are connecting the points through lines.

And over there we have actually it.

### What do we usage contour present for?

In ours example, edge lines represented consistent elevation and also showed the topography that the landscape.

But meteorology (isopleth), magnetism (isogon) and even drive-time (isochrones) additionally use contours for different purposes.

The closeness the contours shows slope. Irregular contours mean rugged terrain. It’s rare in nature because that contours come cross. Yet they deserve to for overhangs and also cliffs.

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What are some other types of border you’ve checked out in nature?

### References

Topographic Maps: The Basics, natural Resources Canada, 2020. Reproduced v the permission that the department of natural Resources, 2020.