Steam clouds rise above the Danau Asam fumaroles on the west side of lake Asam within the 8 x 16 km Suoh depression in SE Sumatra. Numerous hot springs occur along faults within the depression, which contains the Pematang Bata fumarole field. Prior to the largest explosive eruption in Sumatra during historical time, which took place in 1933, the floor of the Suoh depression was a broad marsh 13 km long in a NNW-SSE direction. The depression appears to be primarily of tectonic origin, but contains historically active maars and silicic domes along its margins. Anonymous photo, 1990.