Papandayan is a complex stratovolcano which is found in a row of volcanoes. It has very distinctive yellow crater walls due to coloring by sulfur. The crater is surrounded by forest and extends to the northwest by a long, steep chasm. This chasm becomes a river channel at the foot of the mountain.
The highest part of the crater floor lies to the southeast. It is ~6600 feet (2000 m) high and sits ~800 feet (240 m) below the crater rim. The floor of this crater contains sulfurous pools of standing water, fumaroles, solfataras, mud volcanoes and hot springs. All this minor volcanic activity makes it quite noisy on the crater floor. A river which flows across the floor of the crater begins as a clear stream in the forest but quickly becomes heated and filled with sulfuric acid as it flows across the floor. The mud volcanoes on the floor of the crater are normally 2-4 feet (0.6-1.2 m) high and explode with great force. They eject hot, muddy water every 20-25 seconds.
This complex stratovolcano has four large summit craters, the youngest of which was breached to the NE by collapse during a brief eruption in 1772 and contains active fumarole fields. The broad 1.1-km-wide, flat-floored Alun-Alun crater truncates the summit of Papandayan, and Gunung Puntang to the north gives the volcano a twin-peaked appearance. Several episodes of collapse have given the volcano an irregular profile and produced debris avalanches that have impacted lowland areas beyond the volcano. A sulfur-encrusted fumarole field occupies historically active Kawah Mas ("Golden Crater"). After its first historical eruption in 1772, in which collapse of the NE flank produced a catastrophic debris avalanche that destroyed 40 villages and killed nearly 3000 persons, only small phreatic eruptions had occurred prior to an explosive eruption that began in November 2002. (Description from SI/USGS)
Sources of Information:
Junghuhn, F., "Java, Its Shape, Covering, and Internal Structure: Part 2," p. 109-112, 1853.
The SI/USGS Global Volcanism Program