Sometimes, It’s a Bumpy Ride

When I first looked at maps of Alaska, I wondered why it showed so few roads and decided (wrongly) that the map was only showing the major “highways.”  At one point, I suggest to Timm that we visit a remote area and he explained that we couldn’t get there by driving because there were no roads to take us there.  “No road?? What do you mean there’s NO road?" I asked.  I didn’t understand how there could be NO roads.

I soon learned that the vast majority of Alaska is wild and remote, accessible only by plane or water ferry.  This includes the capital city of Juneau.   Furthermore, I came to discover that many of the so-called major roads shown on the map are gravel!  Gravel?  Yes, miles and miles of gravel.  The below map shows these gravel roads marked by a blue circle. 

Map of Alaska.  Copyright © U.S. Public Affairs Resource Center

Consequently, during this past month that we’ve spent in Alaska, we’ve driven our share of miles on gravel and dirt roads.  Invariably, as we’ve driven on gravel roads we’ve run across washboarded roads.  Anyone who’s driven on a gravel road knows the feeling of driving on washboarded road.  Your car’s suspension takes a beating while you shake up and down.

Washboarding on the gravel road in Kenai National Wildlife Refuge 

Bouncing along one day, I said to Timm, “IIIIII wondder whatttt cauusssess, wasshhhboaarding.”  He replied, “IIIII doonnnttt knoooww eiiithheerr.  Whhheennn weeee geettt hooommme, leeetttss loookkk itttt uppp onnn theee inteeerrrneettt.  So I did.  

We know intuitively that washboarding is caused by cars driving over the dirt road.  However, what are the physics behind the creation of those uniform ripples?  What happens is as vehicles drive over loose material on the road, each small bump in the road causes the tires to build up the material ahead of the tires while simultaneously digging out a small hole behind the tire.  It’s similar to a stone skipping across a lake: each time the stone hits the surface of the lake, it pushes a bit of water in front of itself while leaving a divot of water behind itself.  Similarly, the car tire has the same effect on the relatively soft dirt underneath it.  As each additional car drives over the road, it pushes more dirt forward and creates a divot until a ripple forms.  Many cars driving at approximately the same speed create the nice, uniform ripples.

Most of Alaska is vast stretches of roadless land, absent of people and inhabited by only wildlife.  Many of the main roads are really just dirt paths pretending to be a real road.  Alaska is indeed, the last frontier.

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