Long Coastline

February 7, 2016
By Damond Benningfield
Episode:

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Coastline at Mustang Island State Park. Credit: Texas Parks and Wildlife

If you ever decide to walk America’s coastline, you better make sure someone’s taking care of your dog — it’s going to take a while. According to NOAA — the National Oceanic and Atmospheric Administration — the ocean coastline stretches for 88,633 miles.

Actually, NOAA has two measurements for the coastline. The other yields a length of just 12,383 miles. And both measurements are a bit arbitrary. That’s because there’s no internationally recognized definition of what a coastline really is.

To get the shorter number, for example, NOAA uses something called “general” coastline. It’s compiled from maps that are relatively coarse — like a single map of the entire country, where all the intricate detail is turned into smooth, even lines.

When you go on your coastal walk-about, though, you probably don’t want to use that system, because you’ll end up walking right into the water. Instead, you’ll want to use the system that yields the much longer coastline. It’s compiled from much more detailed maps — those that show only a small portion of the coastline.

This system, known as “tidal” shoreline, includes all the contours of bays and estuaries, for example, plus the detailed outlines of islands, capes, and other bits of land. The system even measures the mouths of rivers and creeks up to a certain point inland.

Not surprisingly, the state with the longest coastline is Alaska, with almost 34,000 miles along the Pacific and Arctic oceans — a pretty good jaunt all on its own.