Making realistic lava using pure vector art is difficult. Fortunately, for this isometric version, I wanted a more "sketch-like" representation, but one that was still recognizably lava. I'm satisfied with how it turned out. Gets the message across, at least. Here is a 800% view of the lava in location 14e:



For the horizontal sections, the main object uses no stroke and a dark red fill. On top of this are squiggles with a simple orange brush. On top of this are a big loopy-loop line with a randomized scatter brush (yellow-orange fill). I made the brush with some blobby shapes, rotated and skewed into an isometric look. The brush randomizes on size and position quite a bit, but only changes orientation slightly (keeping the right isometric feel).

Based on photos I looked at of real lava, when slow moving magma becomes a "waterfall", it brightens (usually because the hotter magma on the bottom falls first). So, the color scheme was inverted for the vertical falling lava sections. The background is the yellow-orange (actually, most are really a gradient which are yellow-orange most of the way, then fading into the dark red of the horizontal background, with the angle chosen to match the direction of the map as needed), the same squiggles in orange, then a different scatter brush in dark red. To give the illusion of falling, I stretched out some ovals for this brush, randomized much as the other one.