Hill pointed me to a nice time series of US underground nuclear
tests. I made a time series of it with the height of the icon in meters equal to the yield in KT. I'm afraid the lat and lon coordinates are not too accurate but it's still pretty interesting..
To use the time series, I believe you need to have the EC version of Google Earth. Go to the <tools> menu and enable <time>. After the meu pops up check "Enable Time" and you should be able to select placemarks with the time slider.
For more on nuclear tests check out Hill's great pages:
USSR PakistanIndia China France UK USA