There are many interesting crater lakes around the world and many are exciting natural wonders. Some of the most surprising are the three Kelimutu crater lakes in Flores island, Indonesia.

Crater lakes

Bowl-shaped hollows near the summit of volcanoes – craters – often are filled with lakes. Most of their water comes from rain and also small streams. Crater lakes “sit” on the top of volcanic vents and often through these vents in the lake water are injected gases, sulfur, metals, and other substances.
Thus volcanic crater lakes are quite unusual. Frequently these lakes are acidic – volcanic vent injects sulfur, which reacts with water and creates sulfuric acid. Sometimes these lakes consist of almost pure acid.
The color of water in volcanic crater lakes also might be unusual – these lakes can be light blue, green, white or even red.

Wonder of Kelimutu


Kelimutu is dormant stratovolcano – steep-sided volcano with crater on its top. Around the summit of volcano has developed lush tropical forest with rare and even unique species. Some of the best known are two unique plants: uta onga Begonia kelimutuensis and turuwara (Rhododendron reschinum).
There have been no large eruptions in the historic time – only comparatively small phreatic eruptions, e.g. steam explosions, as the groundwater reaches magma. Last took place in June 1968.

Kelimutu crater lakes

On the eastern summit of Kelimutu are located three crater lakes – each with its own geochemical and hydrothermal regime. Thus, even if they are located close together, each of these lakes lives its own life.
As a result, each of Kelimutu crater lakes has its own color and this color changes over time irrespective of the changes in the other two lakes.

Kelimutu crater lakes - Tiwu Ko'o Fai Nuwa Muri and Tiwu Ata Polo
Kelimutu crater lakes – Tiwu Ko’o Fai Nuwa Muri and Tiwu Ata Polo / H. Hansson, Wikimedia Commons / CC-BY-SA-3.0
These lakes are:
Tiwu Ata Bupu (Lake of Old People), also Tiwu Ata Mbupu. This lake is up to 67 m deep and has a diameter of 260 – 360 m. It stands a bit separately, further to the west and usually is blue. Kemmerling in 1920ies reported about fumarolic activity around this lake – now it is not observed anymore. Around the shoreline has formed a film of volcanic minerals in bright red, orange and yellow colors, gypsum crystals are forming in the cracks near the lake. This lake has a small, weak input of volcanic gases;
Tiwu Ko’o Fai Nuwa Muri (Lake of Young Men and Maidens), also Tiwu Nua Muri Koohi Fah. This lake is approximately 300 – 430 m wide and up to 127 m deep. Kemmerling in 1920ies reported about fumarolic activity above the shoreline of this lake as well but now it is calm here too. An underwater fumarole is located under the center of this lake. This might be sulfuric fumarole because on the surface of the lake is forming a yellow froth, which is pushed towards the shores. This lake could have copper-rich sediments. Currently, this lake has more active fumaroles than the others – an influx of sulfur dioxide per day reaches 85 tons;
Tiwu Ata Polo (Bewitched or Enchanted Lake). It seems – under the northwestern part of this lake is fumarole – often there is observed a white froth and bubbles on the lake’s surface. Lake is some 330 – 400 m wide and up to 64 m deep. This is an acid-saline volcanic lake where the color changes could be a direct result of changes in the oxidation state of the lake’s water.

Both last lakes are located close together and are divided by a natural dam, which raises some 35 m above the lake level. The dam is not stable – one day it may collapse and both unique lakes would turn into one.

Color changes

All three lakes are fed by similar volcanic gases but the supplied amount and chemical content of this gas fluctuates for each of the lakes separately. Thus, thanks to complex chemical processes of oxidation and reduction the color of lakes is changing over the time. For example, in January – November 2016 the color changed six times.

Kelimutu crater lakes from above, Flores / Tom Casadevall (U.S. Geological Survey), Wikimedia Commons / public domain
Main determinant of the changes in the color of lakes is the content of oxygen. If there is less oxygen in the lakes, they become more green. If lake is rich with oxygen, its color is deep red to black.
A process of oxidation is influenced by the rain and input of volcanic gases and groundwater. As lakes are not connected, chemical processes in each of them are independent – thus also their color changes independently.

Thus Kelimutu has obtained unique natural decoration – three lakes which always have different colors. There is no other volcano on Earth with similar phenomena.


Locals, of course, have known about these lakes since antiquity but first known European to reach them could be French naturalist Leroux, who mentioned these unusual lakes in his travel log in 1896. A more extended scientific description was made by the Dutch colonial geologist Kemmerling in the 1920ies.

Over time lakes have been much studied and the chemical processes of the unique lakes are more or less clear. At the same time, proper volcanological monitoring system here still is missing.

In 1992 was founded Kelimutu National Park with an area of 5,300 hectares and over the last decades, there has been reached certain equilibrium between the interests of nature conservation, local people and increasing stream of tourists. Tourists now love to visit the summit of Kelimutu in sunrise and enjoy the unique view on three diversely colored lakes basking in the lush light of rising Sun.

Kelimutu crater lakes are included in the following list:

Cave of the Crystals, Mexico
Cave of the Crystals / Alexander Van Driessche, Wikimedia Commons / free for use
40 unique natural wonders of the world[/caption] This article is a kind of wonder by itself: after meticulous work of several years here has been collected a list of absolutely unique places, where nature has outdone itself and created something unique, just in one example.


  1. Dr. Gregory B. Pasternack. Keli Mutu. Accessed on September 16, 2018
  2. Gregory B. Pasternack and Johan C. Varekamp. The geochemistry of Keli Mutu crater lakes, Flores, Indonesia. Geochemical Journal, Vol.28, pp.243 to 262, 1994
Kelimutu crater lakes on the map
[travelers-map height=320px this_post=true init_maxzoom=9]
Location, GPS coordinates: 8.767335 121.8170 E
Categories: Volcanoes, Lakes and streams
Values: Geology, Visual
Rating: 4 out of 10 stars
Where is located? Asia, Indonesia, Lesser Sunda Islands, East Nusa Tenggara, Ende Regency, volcano near Moni town
Height: 1,639 m (summit of volcano)
Alternate names: Keli Mutu

Landmarks of Indonesia

The blue fire of Kawah Ijen, Indonesia
The blue fire of Kawah Ijen / Dodi Mulyana, Flickr / CC BY 2.0
Indonesia is a true land of wonders. There are few other countries in the world which can offer similar array of diverse, unique and beautiful natural and cultural monuments.


Mount Cleveland, Aleut Islands
Mount Cleveland / NOAA Photo Library, / CC BY 2.0

This category includes most unusual and interesting volcanoes of the world.

Over the last 10,000 years in some 1,500 places around the Earth through the crust of the planet has been emitted lava, ash and gases from the mantle of Earth. Each of these places could be considered to be an active volcano. Every year some 50 – 70 volcanoes are erupting, at any moment there are some 20 – 30 eruptions on-going.

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