Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported a significant increase in the lake water temperature at Kelimutu’s Crater II (Tiwu Koofai Nuwamuri). The temperature of the lake water rose from 25.3 degrees Celsius (C) on 18 August to 34.2 degrees C on 26 August. A very strong sulfur odor accompanied the temperature increase along with the appearance of gas-and-steam on the lake’s surface. The color of the lake water had not changed, remaining light blue. There was no significant change in seismicity. The Alert Level remained at 1 (on a scale of 1-4) and the public was advised to limit activities near the craters, not approach the lake water, and to not spend the night in the craters.

Geological Summary. Kelimutu is a small, but well-known, Indonesian compound volcano in central Flores Island with three summit crater lakes of varying colors. The western lake, Tiwi Ata Mbupu (Lake of Old People) is commonly blue. Tiwu Nua Muri Kooh Tai (Lake of Young Men and Maidens) and Tiwu Ata Polo (Bewitched, or Enchanted Lake), which share a common crater wall, are commonly colored green and red, respectively, although lake colors periodically vary. Active upwelling, probably fed by subaqueous fumaroles, occurs at the two eastern lakes. The scenic lakes are a popular tourist destination and have been the source of minor phreatic eruptions in historical time. The summit is elongated 2 km in a WNW-ESE direction; the older cones of Kelido (3 km N) and Kelibara (2 km S).

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)