An isopleth is a map whose coloring is based on some smooth, continuous, non-geographic variable. Of course, day to day, most of us just call these “heat maps”. In this case, dialect differences around the U.S.
I’ve posted about this before (here and 9!!! years ago here), but Joshua Katz has a bunch of beautiful new ones. This meme is popular on the internet this week, so everyone is citing the article from Business Insider, but missing his main site with about 6 times as many maps.
Including this one: the classic is whether you call it pop, soda or coke:
I can remember when I was a kid growing up in Buffalo that someone asked for a soda once and I didn’t know what they meant. And I can remember getting a warm fuzzy when I first moved to Utah from Alabama when I was 26 that I was back in the pop zone (although it apparently isn’t strong enough to show up well on this map).
But, there’s other cool ones too (keep in mind that for a lot of them, the regional differences aren’t that obvious), like what do you call a potato bug: