PVMBG reported temperature increases at all three of Kelimutu’s crater lakes and water-color changes at two of them based on 14 and 28 July field observations and webcam images. The variations were most significant at Crater I (Tiwu Ata Polo). The color of the water changed from brown on 14 July to blackish brown on 28 July and the temperature increased from 19 to 22 degrees Celsius. Water bubbles and/or upwelling in the NE part of the lake were observed on both days. At Crater II (Tiwu Koofai Nuwamuri) the water color was turquois green on 14 July. Light-yellow to golden-yellow sulfur deposits were floating on the water in the central part on the lake and along the S edge of the water on 14 July. There was a minor sulfur odor and the water temperature was 25 degrees Celsius. By 28 July the water color had changed to light blue and light-yellow sulfur deposits were scattered on the surface in the central part of the lake and along the margins. A sulfur odor was present and gas plumes rose as high as 100 m above the water’s surface. The water temperature had increased to 33 degrees Celsius. The color of the lake water at Crater III (Tiwu Ata Bupu) remained at dark green during 14-28 July, but the temperature increased from 16 to 19 degrees Celsius. Though the activity indicated increased activity within the hydrothermal system, the Alert Level remained at 2 (on a scale of 1-4) and the public was warned to stay 250 m from the crater rims.

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)