Mount Karthala is an active shield volcano of 2,361 metres that is most of the island of Grande Comore, in the Comoros, with a summit caldera three kilometres across that still steams, and its porous lava swallows the rain so completely that the island has not a single river, and it is climbed over two days with a Comorian hiking club from the villages on its slopes. The volcano erupted in 2005 and 2006, showering the island with ash, and its flows have reached the sea again and again, paving stretches of the coast in black rock and grey volcanic shingle, so that the shore below the mountain is lava and the water off it drops steeply, which brings the humpbacks that calve here in the southern winter close in within sight of the black beach; the climb starts in villages of banana and vanilla, goes up through rainforest and into a belt of giant heather, where the trees shrink and then quit and the path runs through waist-high heather and ferns rooted in loose ash, to a camp near the rim. Comorian clubs climb most weekends, and joining one turns a hard slog into a shared one, with guides and porters who read the cloud and know where the trail vanishes.
The rim is reached in the dark, since by mid-morning the cloud usually seals the summit for the rest of the day, and at first light the caldera opens below, a floor of grey ash and black lava, and the island and the sea beyond. The Karthala scops owl exists on this volcano and nowhere else on Earth, calling in the forest belt at night, and the lava does not stop at the shoreline, since the coelacanth, the living fossil fish, was found alive in the deep water off the volcano's submarine slopes in the 1950s, in caves in the lava. The descent is the same way, on ash that slides. Karthala is a mountain that is an island, and it is still breathing through its top.