Sketched in Sand

I mentioned this on Twitter yesterday, but saw no reaction- no retweets or favorites- so I presume most of my geo-type followers missed it. And it's much too cool for me to let that happen. A friend e-mailed me the link to this site yesterday, and the story told by this picture (and many others) is really quite amazing...

So what do *you* see in the above design? Hmm?

I'm betting "seismogram" was not the first thing to pop into your mind...