And good place to drop few links, if you'd like to cut to the chase.

The finished notebook from the screencast (which you can fork): https://beta.observablehq.com/@jashkenas/earthquakes

And a fancier version that spins, reuses the canvas element instead of re-rendering it from scratch, projects the quakes as circles on the surface of the sphere, and offers a bunch of other options to configure (like if you'd like to chart the past day, week or month of quakes): https://beta.observablehq.com/@jashkenas/quakespotter-0-1