How a City Can Be Below Sea Level Without Necessarily Being Completely Submerged in Water

In a briny episode of “Things You Might Not Know“, host Tom Scott travelled to Calipatria, California known for being the lowest elevation city in the western hemisphere. While standing next to the city’s famous flagpole, Scott explained why Calipatria is not submerged under water despite being 184 feet below sea level, what the term sea level actually means, how it’s calculated and how the earth is truly shaped.

What is sea level? In theory, it is the average height of the sea around the Earth. But there are some problems with that. Problem 1: the Earth isn’t a sphere. I mean, it’s vaguely a sphere, don’t get too excited, Flat-Earthers. It’s a bit squashed. The force of its own spin makes it bulge by a few kilometres around the equator. And when you’re defining height above sea level in metres, that’s a lot. So geographers solved that by defining the Earth as an oblate spheroid. Basically a smooth squashed sphere, just in fairly precise mathematical terms.