Most of the ice at the caps is floating ice, so melting that ice would have zero effect.  Melting the Greenland ice and the ice on land in Antartica would, at the very most, raise the sea level by thirty feet.

Anyways, the last place you want your lair to be is in the ‘high-res’ satellite image areas of Google Earth.

I am a geologist, and I went to grad school in SoCal and have been out to look at stuff in this area, but I’m not particularly familiar with it and there isn’t more detailed info on the map. So I’m not sure if the lava flow been more accurately dated than that, but it probably has been. The focus of that map is on the recent stuff (Quaternary deposits) so leaves out the details of the older stuff.

Anyway, mini volcanoes like this are not particularly common, but there are a few places in the US where you can see them. Anywhere with a major lava flow independent of mountain-building events will have them (you see lava and stuff elsewhere in California that is related to the processes that created the Sierras etc.) Another notable one is at the Snake River Plain in Idaho and there are a whole bunch of small volcanoes like this that you can see from the highway as you drive through.

Seriously, has this thing been in any movies? It looks weirdly familiar.