CVGHM reported that on 6, 10, and 12 June, and during 14 June-9 July, the color of the water in Kelimutu’s Crater II (Tiwu Nua Muri Kooh Tai Crater) was bluish white. Diffuse white plumes rose as high as 50 m above the lake’s surface and in some areas the water appeared or sounded like it was boiling. A sulfur odor was also reported. The water in Crater I (Tiwu Ata Polo) was light green and churned, and the water in Crater III (Tiwu Ata Mbupu) was mossy green.

During 22-29 June sulfur dioxide concentrations from Crater II were occasionally detected at 2.8 ppm, when the wind blew the gas towards the sensor. CVGHM noted that plumes rising from the lakes became lower and barely visible during 3 June-9 July, and that the “rustling sound” of water from near the dividing wall of craters I and II gradually faded away. Based on visual observations, seismicity, and gas emissions, CVGHM lowered the Alert Level to 1 (on a scale of 1-4) on 12 July.

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)