Crossing into the caldera at the summit was great, very beautiful. There are several large cones (extinct vents) that have formed on the old rim, each a bit different and all beautiful. The rim is steep and pretty obvious that it is a caldera (don't know when it formed, doubt if anyone does).
Inside it is lush and green, mostly planted in coffee. We passed through a couple small villages. I took photos of houses with the vent fuming in the background. We visited a blocky lava flow and were amazed at how similar the textures and composition are to our rocks, a good educational stop (uniformitarianism at its best).
The set up for climbing to Ijen's crater is pretty well organized by Java standards. A real parking lot, trail head, sign in book and a few groups of people about. The hazard map for Ijen (lahars and pyroclasts) was posted (12,000 people in 70 villages live in a 10 km radius of the summit). The trail went up fairly steeply, about the angle of repose. Most of the time we were in good forest complete with tree ferns, at least three types of ground ferns, and beautiful trees, some with yellow flowers. Felt like Hawaii forest. Almost immediately we encountered men carrying sulfur blocks down from the summit (see below).
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