Mount Nyiragongo is a fascinating
spot, hosting one of the world's rare "permanent" surface lava lakes. The Big Picture recently featured a
dramatic photo essay of the June 2010 expedition to the crater, including what is believed to be the first successful attempt to reach the actual edge of the lake and survive. (Note: in Google Earth, the best way to get the actual spot is to enter "Mt Nyiragongo, Democratic Republic of the Congo" into the search box, which should get you a spot high on the North rim.) For a more scientific report with some interesting info, see the
Smithsonian Global Volcano Program page, which I have used for some of the more specific numbers; but go look at the amazing photos first! In particular,
#20 is both a dramatic picture that puts a scale to the whole thing, and perhaps the closest depiction of what it would look like when a dwarf goes to tap a volcanic pipe that we're ever going to get in reality. Some additional information, and some older but still interesting photos, are at
PhotoVolcanica's page, focused mainly on the 2002 eruption.
The lava lake is approximately circular, between 220m and 230m (720' - 755') across; this is probably larger than an entire embark square (48x48 dwarf-cubes, which depending on debate are probably between 3' (~0.9m) and 20' (~6m) across, and typically assumed to be on the lower end of that range; I personally tend to think something in the 5' (~1.5m) to 2m (~6.5') range is the best fit, and will use 2m from here on for simplicity, so a dwarf-tile is 4 m^2 and a dwarf-cube is 8 m^3). So about 112 tiles across; a 3x3 embark would barely encircle the central pool with enough room to work around the edges, and it has roughly 10,000 tiles of lava at the surface.
If the lava lake were ~500 m deep and in the shape of an inverted cone, with 40 m and 225 m for bottom and top diameters, respectively, the team conservatively estimated its volume as approximately 7.5-10 x 10^6 m^3
That's equivalent to roughly a million dwarf-cubes of magma to work with, and it refills rapidly...
Since the last eruption (January 2002), the surface of the lava lake has risen regularly (figure 46). The surface ascends towards the crater rim due to a constant influx of magma at an approximate average rate of ~4.8 m per month (~57 m/year).
Call it 2 new cubes in height per month, or about 20,000 more cubes every month... how's your pumping system?
The lowest (ε, epsilon) terrace looks like it would neatly fit a 5x5 embark. Going up to a 7x7 or 8x8 embark should get you most of the γ (gamma) terrace, where the team set up their camp as seen in #10. The volcano as a whole pretty much fills a region tile; the rim is about 1300m across, so you'd need something like a 14x14 embark to have any substantial amount of land on the outward-facing slopes all around. The inner slopes are also quite steep; see
this preliminary scale drawing from the SI page, and note that unlike most drawings of the type, the vertical scale is NOT exaggerated.
We badly need a "region painter" so that this sort of thing could be set up... or better yet, world generation that was capable of randomly generating this sort of thing on its own in high-vulcanism worlds!
Edit: There was a more recent (Jan. 2011)
expedition to Mt. Nyiragongo, which while it didn't get nearly as close to the lava still got some
excellent pictures.