Example of an Isarithmic Map

I found this map online and thought it was a neat example because of everything that's going on! I can't imagine how long this took whoever drew it out, but they did a good job. It's a geologic map but the legend is too small to read unfortunately, even on the main page. Visually it is a good Isoline map!

http://www.esf.edu/es/felleman/USGeolMap.gif