National Old Rock Day

When I was a kid, we took a trip to the desert near Borrego Springs, CA and I found a really cool rock that turned out to be fossilized coral.  I couldn't believe that the desert I was standing in had once been completely underwater.  I still think about that every time I fly over the desert.  From above, it kind of looks like an ocean floor.
So for today's holiday, National Old Rock Day, I thought back to that discovery in the desert :)