History

Maybe one day there will be made a series about tanzanite. An attempt at the scenario by Wondermondo:

The first episode: “False start”

In January 1967 young Maasai man Ndugu Jumanne Ngoma was going to visit his relatives in Kiteto village. As he crossed the low Merelani Hills, he noticed something unusual – blue, transparent gems. He was not in a hurry – thus he stopped and started to pick up these stones. Over the course of several hours, he collected some 5 kilograms of these natural wonders. The value of this find today would be at least one-two million US dollars.

When Ndugu reached Kiteto, his friends advised him to take a bus and go to Nairobi to sell the blue stones in the gem market. There he definitely will get better profit than in the nearby Arusha town.

Thus Ndugu borrowed some money and went to Nairobi. He found an office of gemstone dealers, went in, and showed the gems. “Leave them here, we will determine their value (if any) and will send an answer to you somewhat later” – said dealers, and the simple country boy agreed – just asked for some money to return home.

It seems, these dealers still are busy trying to find out the value of these stones, and Ndugu (if he is in good health) still is waiting for the message from Nairobi…

The second episode: “It begins”

In the same January 1967, another Maasai man Ali Juuyawatu noticed a cluster of deep blue crystals on the ridge of Merelani Hills. He told about this find to tailor and gold prospector, Portuguese Manuel d’Souza, or, as he was known among locals – Mad Manuel.

Mad Manuel picked up these stones – they definitely looked interesting, although it was not clear what kind of mineral it is and what could be its value. Stones looked like sapphires but had an unusually vibrant color.

Manuel showed the stones to geologist John Saul but the latter also could not determine them and decided to send the stones to his father, another geologist Hyman Saul in New York. Saul-elder brought stones across the street to the Gemological Institute of America and specialists there determined that this mineral is zoisite.

In the meantime, several more geologists in Tanzania received samples of this stone and their decision was the same – this is a very unusual variety of zoisite.

The third episode: “Tiffany”

International jewelry giant “Tiffany & Co” noticed these blue stones early. And they – gem cutters, designers, marketing specialists, and, of course, managers – acted fast. In 1968 consumers were introduced to a new, beautiful gemstone named “tanzanite” through a sophisticated marketing campaign.

In fact, geologists initially called the stone simply “blue zoisite”. Jewelers at Tiffany were not happy about this – after all, this sounds a bit like “blue suicide”. Try to sell something with such a name!

Meanwhile, the country of origin – Tanzania has a beautiful, tuneful name. Thus – tanzanite! The marketing campaign of Tiffany declared that this is the most beautiful gem discovered over the last 2,000 years, and stones were included in beautifully crafted rings, necklaces, and brooches. This definitely was a big success for “Tiffany & Co”, well-timed and well-executed. Tanzanite is one of the main gemstones in Tiffany’s jewelry up to this day.

The fourth episode: “Mad times in Merelani Hills”

People headed towards Merelani Hills. We have heard these stories – whether this is a gold rush in Alaska in the 19th century or the mining of diamonds in West Africa now, human nature stays the same. Thousands and thousands of people were digging through the cliffs and dust of Merelani Hills in 1967 – 1971. Everything of value disappeared from the surface of hills in some months’ time and people started to dig deeper in the ground for the next stones. They were disturbing each other, pits and shafts frequently collapsed, and most did not find anything and were increasingly irritated. Conflicts were commonplace, just as theft and heavier crime.

Tanzanian government interfered in 1971 (by that time some 2 million carats of gemstone were mined) and nationalized the mines. But this did not change much – the chaos in Merelani Hills continued. Sometimes up to 30 000 people were working side by side in this small plot of Tanzania and in total, some 70 000 people earn their income thanks to the tanzanite.

The fifth episode: “The big guys know it better”

In 1990 the find of tanzanite was divided into four blocks – A, B, C, and D, where the mining rights in B and D were given to local miners, but A and C – to large operators (now small miners are also in A block).

Since 2004 block C is operated by the company “TanzaniteOne Mining Limited” – a mining company that strives to be a showcase of ethical business. And, indeed, mines (up to 800 meters deep!) of this company are a lot more safe and comfortable than in the other sectors, workers are better protected socially, tanzanite stones are getting added value (sorting, cutting) in their home country – Tanzania.

In order to promote knowledge about the real value of tanzanite “TanzaniteOne” has created a subsidiary non-profit organization “The Tanzanite Foundation” which strives to improve the living conditions of the local community and, especially, workers in tanzanite mines. Nevertheless, local miners, which work outside the “TanzaniteOne” sector, consider that “The Tanzanite Foundation” is a typical case of astroturfing – an artificially created pseudo-civic organization that imitates socially important activities in order to retain the control of large companies over natural resources.

What about the other – sectors of local miners? Not much has changed except that mines are going deeper and deeper and work is harder and harder. One needs to descend hundreds of meters into narrow and dangerous ratholes and work through dust and cliffs in search of increasingly rare tanzanite crystals.

The mines are gradually exhausted. In 2011 “TanzaniteOne” mined some 2.5 million carats and earned 24 million USD. Since then the amount of tanzanite and profits are falling, and the number of workers is decreased. Mines go deeper and deeper and it is increasingly expensive to maintain them. Thus it is expected that around 2030 – 2040 the mining may stop here altogether.

Geology and chemistry

Zoisite

Tanzanite is a variety of a rather common mineral – zoisite.

Zoisite also can form beautiful, transparent crystals which are colorless, greenish, grey, or brown. Fine gems are cut from zoisite too – but the value of other varieties is not as high as the tanzanite value.

Blue zoisite of Merelani Hills

Only in one place on Earth is found zoisite in wonderful, deep blue color – this is in Merelani Hills, Tanzania (although some ink-blue gems of zoisite were found also in the Tsavo region, Kenya). This zoisite – tanzanite – is found in a small area that is just 7 by 2 km large. Tanzanite is at least 1000 times rarer than a diamond.

This gemstone has formed in metamorphic rocks and is mined together with several more beautiful gemstones, such as chrome diopside, tsavorite, blue apatite, grass-green tremolite, and another unique gemstone – axinite-(Mg). In Merelani Hills are found the most beautiful crystals of graphite in the world – one more highly valued collector’s item.

Mines in Merelani Hills have been very rich and the quality of mined jewels does not decrease up to this day. Thus, from 1995 to 2005 there were mined some 39 tons of tanzanite.

The largest rough piece of tanzanite was found in 2005. The weight of this stone was more than 3 kg: 16,839 carats. It was named “The Mawenzi” – after one of the summits of nearby Kilimanjaro.

Heat treatment for color

Rough tanzanite is reddish-brown to colorless and there is needed heat treatment to bring out the beautiful blue-violet color. There is needed heat of some 370 – 390 °C for some 30 minutes. The process is risky: if a crystal has some cracks, it shatters in the process.

Sometimes nature creates these blue crystals. Initially, in 1967 there were found beautiful blue crystals on the ground surface. These crystals, most likely, were heated by forest fires. But also deeper in the mines in some places crystals are blue – these pieces of zoisite, most likely, got heat from some geological processes in the past.

Tanzanite by far is not the only gemstone that is heated. For example, some 90% of sapphires, most of the amethysts, ruby, aquamarine, and, other stones are heated as well. Sapphires can be heated at much higher temperatures for weeks, totally transforming the stone.

Thus specialists do not consider the comparatively mild heating of tanzanite to be “cheating” – especially if this happens naturally as well.

Miraculous color effects

The unusual blue color is created by trace amounts of vanadium and/or chromium – similar as in the case of extremely rare blue garnets (see blue garnets of Bekily, Madagascar).

Tanzanite has a very unusual property – trichroism. This means that a crystal of tanzanite changes its color depending on the direction of how one looks. From one side it may be deep blue, from other – purple, and from another – burgundy. There happen to be other colors too: indigo, cyan, green, yellow.

In fluorescent light, the blue color is more intense, in incandescent light the violet hues are more pronounced.

After the heat treatment stone is dichroic – color changes between purple and indigo or blue. Heat treatment removes the brown – burgundy color.

Rarely the stone gets a set of green and blue color. Such stones have much less value as gems, but collectors love them – these stones are especially rare.

The most valuable – deep blue color – is only in 1% of tanzanite samples.

High value

Thus far there has not been noticed synthetic tanzanite or high-quality imitations. This again is rare – and increases the value of the stone even more: if something is sold as tanzanite, a client can be sure that this IS tanzanite.

The price of the highest valued tanzanites may reach 1200 USD per carat and it continues to increase. Tanzanite is also one of the highest valued stones for collectors – even in the largest collections tanzanite takes the central role. Many specialists consider that this is the noblest of all blue gemstones, surpassing even the centuries-long fame of sapphire.

References

1. Tanzanite Foundation. Page accessed in the 1st December 2018.
2. Working the Blueseam: The Tanzanite Mines of Merelani. Now this is a great website! Accessed in the 1st December 2018.

Merelani Hills are included in the following articles:

Legendary geologists

Geologists in Russia have been very special people. Nobody else has crisscrossed the incredibly large area of this country, nobody else knows as much about nature’s secrets here. In the eyes of many common people, geologists are somewhat different – they seem to be away from the political turmoil and hypocrisy, leading to intellectually rewarding and at the same time – physically demanding life far away from civilization. Of course, the reality often is different – but such legends may have some truth in them. Discoverers of charoite: Vladimir Ditmar, Vera Rogova, and Yury Rogov are some of such legendary geologists.

Vladimir Ditmar

The first known person to see charoite was Vladimir Ditmar – an outstanding, adventurous geologist who managed to fill in quite a few white spots on the map of Siberia and the Far East. He and his team researched the Murun massif and in 1948 Ditmar noticed the unusual color of some stones in the bed of one stream – now called the Ditmar stream. He did not have a possibility to research it and just mentioned it as a “cummingtonite slate”.

Before this local people did not notice this unusual stone. They visited the hills only in wintertime. The weathered surface of charoite is not attractive – it looks just like one more common rock.

Vera Rogova and Yury Rogov

For a while, the unusual rocks were forgotten. But in 1960 geologists led by Yury Rogov returned to this area. Once Yuri decided to look at the old shack of Ditmar – and found an unusual stone next to it. He chipped off a piece of this stone to bring it back to his wife – mineralogist Vera Rogova.

Vera immediately noticed a yellow mineral in this sample and correctly determined that this is a new mineral to the science – later it was named tinaksite. But the most attractive feature of this stone was another mineral in gaudy lavender color – a very rare hue in mineralogy. Geologists at first could not believe that such an attractive feature could be something new.

Work in the exciting Murun massif continued and geologists made one important discovery after another. Nearby they found rich ores of uranium and other valuable materials, mineralogists discovered new minerals.

Only in 1973, some gemmologists noticed the outstanding properties of lavender-colored stones, and there appeared first artworks made from it. Serious research started and in 1977 scientific community approved the new mineral, which was named: charoite. Vera Rogova gave this name after the nearby river Chara… but she did not forget about the other meaning of this word. In Russian “chara” means charm, wonder.

Murun massif

The whole Murun massif is a unique natural monument with a very complex geological situation and numerous unique and very rare minerals and rocks. In this area are found some 200 diverse minerals, many of them rare and even unique to this area. Only here are found such minerals as tinaksite, charoite, tokkoite, frankamenite, and murunskite. This remote location is like a paradise for collectors of minerals and gems.

The genesis of this unique geological monument is not entirely clear. It is known that this is a contact of syenite and limestone deposits. The unusually high content of calcium, as well as barium, strontium, zirconium, and other elements, led to extreme mineralogical diversity.

Charoite

Charoite is found in an area of some 10 – 12 km² along the southern margin of the Little Murun intrusion – an especially interesting part of the Murun massif. It has not been found anywhere else on our planet.

This mineral is translucent and massive – thus it is not exactly gemstone. But it has a very unusual, bright lavender-purple color and pearly luster – charoite looks almost like an artificial, visually enhanced material. Also – the stone is quite hardy. Thus it can serve as exclusive material for jewelry, as well as for small utensils – such as cups, bowls, frames, and cases.

Chemical composition of charoite is quite complex and its research took several years. There are different ways to represent it, and one is:

(K,Sr)_15-16(Ca,Na)₃₂[Si₆O₁₁(O,OH)₆]₂[Si₁₂O₁₈(O,OH)₁₂]₂[Si₁₇O₂₅(O,OH)₁₈]₂(OH,F)₄ · ~3H₂O

Mining

Mining charoite is quite hard work. It is nearly impossible to transport heavy machinery to this far away location, where some 1000 km needs to be made without any proper roads, reaching the height of 1.5 km above sea level. The sturdy rock cannot be blown up – this would damage the unique mine forever. Thus the stone is mined carefully and rather slowly by other methods, involving much handwork.

The known stock of charoite in this area is more than 100 000 tons. The Sakha Republic has limited the mining of charoite to 100 tons per year – thus the mines will be used for a long time and the mined material would be used carefully, for high-value items. On the side of Irkutsk Oblast charoite currently is not mined. The price of raw charoite is around 30 – 700 USD per kg, especially valuable is the charoite which was mined in the 1970ies.

It is highly possible that there is produced fake charoite as well.

References

1. Рогова Вера, История открытия чароита и других минералов, Petrographica.ru. 7 November 2010. Page accessed in the 28th November 2018.
2. Images of the mining process and the mine, 11th September 2010. Page accessed in the 28th November 2018.

Sireneviy Kamen is included in the following articles:

Lakes have been isolated from the outer world for at least 120 thousand years and may contain unique life forms. Thus far there are not known other similar lakes in the world.

Subglacial lakes

Subglacial lakes are not too rare. There are known more than 400 such lakes under the ice sheets of Antarctica and several such lakes under the ice sheet of Greenland and some other places.

These lakes are squeezed between the ground and an enormous ice shield. Some of these lakes are small, isolated worlds without contact with the outside world. Famous is the Blood Falls in Antarctica – a seep from one such amazing subglacial water body, which has been isolated from the outside world for more than one million years.

These lakes are in eternal darkness and cold – but there happen to be living beings in them. Such a discovery was made in 2014 in the isolated Subglacial Lake Whillans, Antarctica. Discovery was nothing too “serious” – just microorganisms, but, nevertheless, these microorganisms are very interesting to science and our understanding of the genesis of life in general.

Normally such lakes could exist if the temperature at the base of the glacier is above the melting point. Even in the harsh climate of Antarctica, these lakes are not frozen thanks to the isolation of the thick ice layer above them and warmth from the ground – geothermal heating. Under the pressure of the ice shield, the freezing temperature is a little bit below zero.

First subglacial lakes in Canada

Surprising result of radio-echo sounding

An international team of researchers led by Anja Rutishauser (University of Alberta) was performing radio-echo sounding of the glacier in the far north of Canada – the Devon Ice Cap on Devon Island (by the way, the largest uninhabited island in the world). This was routine sounding and researchers did not expect to find anything special.

Nevertheless, the result was unexpected. The received data had reflective anomalies which testified: below the thick layer of the ice could be lakes. The preliminary results of the research were published in 2018.

T1 and T2

Anomalies were nicknamed – T1 (area at least 500 ha) and T2 (at least 830 ha). The thickness of the ice above T1 is 560 m and above T2 – 740 m.

But there is a hint. Estimates by the specialists show that the base of the Devon Ice Cap is not warm – the temperature at the contact of the bedrock and the ice is around -10.5 – -12°C or even less. This ice shield is located in a mountainous area and the shields are not thick enough to accumulate geothermal heat closer to the surface of the bedrock.

When water is liquid at -12°C? When there is much salt in it!

Hypersaline subglacial lakes

Devon Ice Cap lies over very ancient, Archean rocks as well as newer Cambrian – Ordovician evaporite rocks which to a large extent consist of halite (common rock salt). And – indeed, T1 is located on this salty bedrock and, most likely T2 at least partly is located over it. Thus – yes, T1 and T2, most likely, do not freeze because they contain lots of salt.

In order to remain in a liquid state under the temperatures of -10.5 – -12°C there is needed a salinity of 140 – 160 practical salinity units (PSU) but is highly likely that salinity here is even higher. In comparison, seawater has a salinity of some 35 PSU.

These are the only known hypersaline subglacial lakes in the world. But this status may not hold for long: the salt-bearing Bay Fiord Formation is exposed under some more ice caps of Canadian Arctic islands. Future research, most likely, will bring the discovery of several more hypersaline subglacial lakes.

Is there life?

Hypersaline lakes below Devon Ice Cap have been isolated from the outer world for at least 120 thousand years. It is possible that throughout these long years inside these lakes have survived and evolved unique microorganisms.

Specialists consider that similar lakes could be discovered on other planets or their moons. One candidate is Europa – the moon of Jupiter, which is covered with a shield of ice and has an oxygen atmosphere. Below the ice could be a liquid ocean – and… maybe there are some life forms?

References

1. Anja Rutishauser, Donald D. Blankenship, Martin Sharp, Mark L. Skidmore, Jamin S. Greenbaum, Cyril Grima, Dustin M. Schroeder, Julian A. Dowdeswell and Duncan A. Young, Discovery of a hypersaline subglacial lake complex beneath Devon Ice Cap, Canadian Arctic. Science Advances 11 Apr 2018: Vol. 4, no. 4, DOI: 10.1126/sciadv.aar4353. Accessed on November 27, 2018.

Hypersaline lakes beneath the Devon Ice Cap are included in the following article:

Garnets – colorful gemstones

Garnets are some of the most popular gemstones. These stones are hard, with gorgeous and lovely natural crystals and diverse, bright colors. Group of garnet minerals includes some 25 – 30 minerals with a very similar chemical structure – just the kind of metallic elements changes in the chemical formula. Some garnets include magnesium and aluminum (pyrope), some – calcium and chromium (uvarovite), etc.

Garnets come in all colors. Best known might be the deep red and purple pyropes and almandines, bright orange spessartine and light-green grossular, as well as emerald-colored demantoid (a type of andradite) and bright green uvarovite. Schorlomite is black, several types of garnets are rose-colored, brown, and yellow. Very rare is also colorless garnet (leuco garnet), a rare kind of grossular which can be found in Canada, Mexico, Tanzania, and Burma.

But on the jewelry market, there were not available blue garnets. Until 1997 – 1998.

Bekily blue garnets

Around 1997 there started mining of beautiful garnets north of Bekily, a poor and remote area in the southern part of Madagascar. Searching (and finding!) valuable gemstones is nothing new in Madagascar – this island is very rich with top-class gems and here have been found quite unusual gemstones, such as grandidierite.

At first, prospectors thought that they discovered gem-quality alexandrite – a very valuable color-changing gemstone. To their surprise, this was something even rarer – blue garnet.

Such unusual daylight color amazed gemmologists – blue garnets were something new to them. This was not one or two occasional stones – specialists back then obtained some 160 samples of these unique stones (1.).

Stones were obtained in the gemstone market in Bekily – the location of their find was not disclosed. Now there are rumors that the find has exhausted already in 1999 (2.) but the political and social unrest in the country could also be blamed for this. From time to time some color change garnets still come from these mines but clear blue ones are missing now and in the market can be seen the same stones from the late 1990ies which tend to become more and more expensive with each resale.

The unusual change of colors

These blue garnets are a mix between pyrope and spessartine, with small amounts of almandine and grossular contents. Their color-changing scheme is as follows: in normal daylight, they are blue (the rare best samples) or grayish-blue. In white light (e.g. from LED lamps) they are bright blue. In the usual artificial light, they become red – reddish-purple. Color change, most likely, is created by unusually high amounts of V₂O₃ (vanadium oxide) and some amount of chromium oxide.

Most of the “blue” garnets from Bekily are not really blue but rather grey-bluish, also green-blue. But there are some clear blue specimens. Even rarer are well-formed crystals of blue garnets – prospectors are finding just a shambles of crystals. But at least two crystals of pure blue garnets exist (3.).

Size and price

These stones were small – the largest gem-quality blue garnet in 1999 was just 9.5 carats large. Cut stones are much smaller – 0.1 – 0.8 carats.

Larger blue garnets with a color-change effect are very expensive, with a price exceeding USD 1,500 per carat. But for this high price garnets need to be large and pure blue without the gray or green color. Nevertheless, the more common alexandrite with similar properties could be more expensive.

Are Bekily blue garnets unique?

Color-change garnets from Sri Lanka (finds in Embilipitiya and Athiliwewa) and Tanzania (finds in Umba and Tunduru) have been known since 1979. This always has been a rarity, with some occasional bluish-greenish garnets among them.

Blue garnets, similar to Bekily blue garnets, have been reported in Kenya, Taita-Taveta County since 2009. Nevertheless, the unique stones from the vicinities of Bekily are the main commercially available blue garnets.

References

1. Karl Schmetzer and Heinz-Jürgen Bernhardt, Garnets from Madagascar With a Color Change of Blue-Green to Purple. Gems&Gemology, Winter 1999, page accessed on the 26th November 2018.
2. Ambahatany. Mindat.org, page accessed on the 26th November 2018.
3. Farbwechselnde und blaue Granate. Mineralienatlas – Fossilienatlas. Page accessed in the 26th November 2018. Images of blue garnet crystals!

Blue garnets of Bekily are included in the following lists and articles:

Legends and history

Legends

Humans needed an explanation of this unusual landscape. Due to this locals have several legends about the origin of these hills. Maybe giants hurled piles of the ground at each other and then left the battlefield without cleaning up the mess. But maybe these are dried tears of an unlucky lover – a giant named Arogo.

Present name

The present-day name of the hills is a recent invention by a foreign scientist. German geologist Frithjof Voss saw these amazing hills in 1968 and these mysterious (then) formations fascinated him. In a scientific publication from 1970, he used the nickname “Chocolate Hills” and after some while, the tourism industry took it up. Voss studied the hills with the help of aerial photographs and these studies channeled his career into the realm of aerial imaging and remote sensing. Thanks to this he became a key expert in this area worldwide.

Voss named the hills after their resemblance to a gastronomic treat – chocolate kisses just like the ones produced by “Hershey’s”. Before this some scientists have given other names, e.g. Smith (1924) named them Haycock Hills. But we could agree – Chocolate Hills sounds just nice and tasty!

Geological history

Chocolate Hills are some of the best examples of cone karst on our planet. But… what is “cone karst”?

Karst

Sooner or later water dissolves nearly every rock that exists on Earth. But some rocks dissolve faster: salt and gypsum rocks may dissolve in a few decades – centuries after their formation. Limestone or dolostone, though, dissolves over thousands of years and in the meantime forms amazing geological formations. Just like a melting heap of snow, limestone may form weird-looking, steep residual towers. Water creates channels and caves, streams disappear in holes and reappear somewhere else. All this interesting realm of geological processes in soluble rocks is named: karst.

Karst erosion in tropical regions

If the temperature is higher and there is more water, karst processes become more intense. Thus, in tropical regions, where rainfall is huge and the average temperature exceeds 18 °C, limestone dissolves much faster than in dry or cold regions.

There are places in the tropics where wast, thick layers of limestone are well above sea level and exposed to intense karst erosion. This process has three main stages:

1. Cockpit karst is the first stage. At this stage, the water dissects the limestone layer with numerous caves and trenches. Caves grow larger and collapse, trenches are widening. As a result, a network of deep valleys dissects the limestone massif, leaving limestone ridges in between. Such impressive cockpit karst is in Jamaica, Cockpit Country – hence the name. Limestone soils are fertile – thus the hills and ridges most frequently are covered with lush forest. Of course, this landscape is very hard to penetrate – in most cases, the virgin rainforest still thrives on cockpit karst.

2. Then comes cone karst. As the erosion of the limestone continues, the limestone ridges are divided into separate cone-shaped hills. The larger (wider and longer) the limestone body, the more hills. Yes, and Chocolate Hills could be the most impressive cone karst landscape in the world.

3. Finally comes tower karst. As the karst erosion continues and the sides of the hills become steeper and steeper, at the end remain just a limestone tower. Or – many towers. One of the most impressive tower karst landscapes is Guilin – Lijiang Karst in China where these towers are hundreds of meters tall. As the years go by, the towers fall, dissolve, and… limestone is gone.

Geology of Chocolate Hills

Chocolate Hills consist of hundreds of meters thick Late Pliocene – Early Pleistocene limestone, which has formed on the seabed, above a layer of serpentine. Most of it is formed by corals. Soon after the formation this limestone was raised above sea level and fractured. Rainwater, streams, groundwater dissolved the limestone, gradually forming the present landscape of cone karst.

The repetitive, symmetric form of the numerous hills is explained by the fact that the whole limestone massif raised above the sea level at one time, and erosion processes were similar all over its area. Thus the limestone was dissected by fissures, streams, and caves at similar distances, and all the hills are shaped by the same natural forces. Climatic conditions, most likely, have been the same for a long time and even the distribution of wind direction is more or less evenly throughout the year.

The limestone of Chocolate Hills is rather fragile, sandy. It is rich with fossils – corals, mollusks, and others.

Hills and the whole area contain numerous caves and karst springs. On Bohol are known more than 1,400 caves, but few have investigated them and, most likely, this figure is a lot higher.

Number and extent of the hills

Chocolate Hills are scattered over a large area of Bohol Island. The number of hills is subjective – each can count them as he likes. Some have counted 1 260 hills, some – more than 1 700. In fact, it is not easy to tell where Chocolate Hills end and start other forms of karst landscape – e.g. cockpit karst, which also is widespread on the island.

The height of the hills fluctuates from some 40 m to 120 m and diameter from 65 to 80 m.

What makes Chocolate Hills unique?

Cone karst is not unique to Bohol. Similar formations are found in many other tropical countries – several provinces of China, Jamaica, Cuba, Indonesia (Gunung Kidul area with more than 10 000 hills), the Dominican Republic, and others. Also on the nearby island of Negros, near San Carlos town can be seen similar hills.

But some aspects make the landscape of Chocolate Hills truly unique in the world. The main is: these hills have more or less perfect conical forms and are almost symmetrical. Their slopes are not too steep and cliffs are not exposed – slopes are covered with a uniform cover of grass. Hills always are round or oval, they never have notches or extensions.

Even one such hill is unusual. But if there are hundreds, more than a thousand of them? Landscape consisting of such “copy-paste” elements is unique.

An additional effect is created by the grass which turns brown during the dry season, which usually lasts from February to April. This unusual brown color gave the name to the whole landscape. Grass on the hills has several species, such as Imperata cylindrica and Saccharum spontaneum, here grow also some species of ferns and other plants.

Tourism and nature conservation

Originally Bohol was covered with dense rainforest, although Chocolate Hills, most likely had too weak soil to sustain forest on the steep slopes of the hills. After centuries-long slash-and-burn agriculture, most of the rainforest is gone and now plains between the hills are cultivated – here is grown rice and other crops. Only some 3% of the former virgin forest remains on the island.

Since the 1980ies when the Philippines and also Bohol Island opened to international tourism, Chocolate Hills became a major tourist attraction. The value of Chocolate Hills was recognized by the government and in 1988 there was created The Chocolate Hills Natural Monument, now – “Chocolate Hills” National Geologic Monument. This was not an easy step – the nature conservation efforts led to civil unrest among local farmers, leading to at least two clashes between local guerillas and government forces.

The increasing number of tourists also does not come without challenges: the local tourism industry and authorities thus far are struggling with the proper organization of tourism services. Nevertheless, Chocolate Hills now is the most recognizable natural landmark of Bohol Island and to some extent – all the Philippines and step by step people in Bohol start to earn the benefits of tourism income.

Authorities have developed a viewing deck – Chocolate Hills Complex – near Carmen, where visitors from the summit of one of the hills can enjoy the unusual landscape and learn about the geological history. Another viewing platform is on the top of Sagbayan Hill.

Danger of mining

The limestone of the hills is an important construction material – some hills were just removed by mining. Although the government has strictly forbidden such mining since 2006, locals often continue this activity.

In September 2019 the authorities approved the Chocolate Hills Protection Bill, again completely forbidding any destruction of Chocolate Hills. Trespassers who “successfully” have destroyed one of the hills could be imprisoned for up to 12 years (2).

References

1. Jean-Noël SALOMON, A Mysterious Karst: the “Chocolate Hills” of Bohol (Philippines), Acta Carsologica, Vol 40, No 3 (2011), accessed in 21st November 2018.
2. Renz Antoni, House pushes for Chocolate Hills act, The Manila Times, September 3, 2019, accessed in 14th October 2019.

Chocolate Hills are included in the following list:

The most remote part of Congo jungle?

Some of the most remote and intact equatorial forests are found in the area near the junction of the borders of the Republic of Congo, Cameroon, and the Central African Republic. Here has developed one of the most biodiverse ecosystems in the world – the Congo lowland forest.

Up to this day, this is an immense forest with scattered villages of pygmy people, rich with legends about unusual animals – such as the terrible mokele-mbembe in Lake Tele. Of course, occasional poachers and logging companies are encroaching on these forests as well, and step by step the virginity of this forest is receding.

The missing part of Nouabale-Ndoki National Park

This forest is protected by several protected natural territories. One of them – Nouabale-Ndoki National Park – was created in 1991-1993. The southern border of this national park initially was just a direct line – the local logging company “Congolaise Industrielle des Bois” (CIB) – did not want to see it included in the park because they had a logging concession there. After all this forest is rich with mahogany and other valuable hardwoods – one can make a good profit from it.

Around 1995 the explorers heard the first rumors about a location in the forest south of the national park where animals do not fear people. Soon after researchers managed to pass the dense forest and swamp and reached the equatorial forest between Ndoki (to the southwest) and Goualougo (to the southeast) rivers and their discoveries here have been sensational.

By 1999 there was set up an ape research station, initially by Dave Morgan but soon after he was joined by Crickette Sanz and other scientists and local enthusiasts. Step by step scientists and environmentalists managed to persuade the logging company to abandon its plans to start logging here. In 2001 this unusual forest – Goualougo Triangle – was included in Nouabale-Ndoki National Park.

The pristine forest of Goualougo Triangle

Goualougou Triangle is an absolutely pristine forest where people, most likely, have never lived and few have ever visited it. Even hunters have not reached it. The closest human settlement is Bomassa pygmy village 55 km away.

This equatorial forest has stable climatic conditions – medium temperature here throughout the year is 22 °C.

Here live numerous rare animals and plants, including forest elephants, and western lowland gorillas, but especially common are central (common) chimpanzees. This land is well suited for great apes as the forest supplies them with a huge variety of diverse fruits little known outside this region, such as Treculia africana.

Unique population of chimpanzees

It is assessed that in Goualougo Triangle live some 450 – 750 chimpanzees and some 700 – 1000 gorillas. Contrary to other populations of these animals, here they, at least chimpanzees are constantly innovating and learning new technologies by themselves.

Fearlessness and curiosity

Local animals have not learned the dark side of human nature. Thus chimpanzees and other animals are curious and not afraid to meet humans, they do not escape. Often the opposite happens – chimpanzees are curious and call others to come and look at humans. Sometimes it is hard to get rid of them: people get bored but chimpanzees still look at humans as unseen and weirdly similar creatures. Never before researchers have seen such behavior in chimpanzees. Everywhere else apes are just escaping the humans – and, in order to research them, explorers need years to habituate them.

Human diseases are dangerous to chimpanzees. No doubts, uncontacted groups of chimpanzees have no immunity against most of these diseases. Thus researchers approach apes with surgical masks – to protect the apes from possible illness.

Researchers have decided to habituate just a few groups of local chimpanzees while other great apes in this forest will be less in contact.

The most sophisticated culture of great apes on Earth

Chimpanzees in the Goualougo triangle have one more unusual trait – they have a lot more sophisticated culture of toolmaking than any other population of chimpanzees in the world. Local chimpanzees are purposefully selecting the right sticks or any other tools best suited for their intended activities, e.g. picking out the ants from anthills or getting the honey from tree hollows. Chimpanzees adjust their tools, for example, chew the twigs to get brushes for a better collection of ants.

If they find an especially comfortable tool, apes bring it from one known nut-bearing tree to another finally leaving it at the tree for repeated use. Researchers have observed also that chimpanzees teach their skills to others and how young chimpanzees learn from the elder ones.

Thus far this is the only place on Earth where humans can observe how another species of animals is innovating and learning new technologies by itself. Elsewhere these great apes have no possibility to evolve like this because there is less social tolerance as the apes are persecuted and their behavior is influenced by the constant escape from humans or permanent loss of equilibrium between the groups of animals due to logging or hunting. In socially intolerant conditions the younger generation of apes has no possibility to learn all the skills from the elder generation. They can not continue innovations, based on the previous achievements of their ancestors.

Goualougo triangle and human nature

This makes us think about ancient humans – after all, they had such a possibility to evolve and innovate. The miraculous forest of the Goualougo Triangle may provide some answers about the behavior of early humans.

Unfortunately, this “Last Eden” is endangered – step by step poachers and loggers approach this pristine land. The area around the Goualougo Triangle still is mostly pristine, but if it will be logged, also Goualougo Triangle will change, even if left untouched.

References

1. Goualougo Triangle Ape Project, accessed in 5th November 2018
2. Joshua Foer, The Truth About Chimps, National Geographic, February 2010
3. Crickette M. Sanz, David B. Morgan. The social context of chimpanzee tool use. Accessed in 5th November 2018

Goualougo Triangle is included in the following articles:

How this cave was created?

Geological history of Kitum Cave

Mount Elgon (4,321 m tall) is an ancient shield volcano, which formed at least 24 million years ago and is extinct. This is an enormous, wide mountain which step by step rises above the dry plains of Kenya and Uganda. As the land rises, climate and vegetation change – and at the height of some 2 – 3 kilometers above the sea, there is a thick forest with many rare plants and animals and a comparatively cool climate.

Small streams flow through the forest and at the ends of ancient lava tongues, small waterfalls are forming. Here the force of falling water creates small grottoes behind the curtain of the waterfall. Most likely Kitum Cave started to form from such grotto behind a waterfall. After all – there still is a waterfall at the entrance of the cave.

Salt

Kitum Cave has formed in pyroclastic rocks – e.g. rocks that have been created by an erupting volcano. Here are several diverse layers, most likely created by several eruptions. Above is a layer of hard volcanic agglomerate and below it – somewhat softer rock.

The softer lava contains soluble salts. The upper layer protects it from the water thus salt still is there. The damp air behind the waterfall, in the hollow, is leaching from this lave pure sodium sulfate and wonderful, fragile crystals of mirabilite are forming on the rock surface.

In fact, salt crystals in these caves are some of the best anywhere and Kitum Cave has not only mirabilite but other salt crystals as well: halite, anhydrite, polyhalite, natron, and others.

Lava has preserved the remnants of the plants which were growing here in the Miocene epoch and were eliminated by the eruption of Mount Elgon. Visitors can admire fossils of large tree trunks, tree branches, and even occasional bones of extinct animals in the ceiling of the cave.

Elephants

Just like any other animal, elephants need salt to stay healthy – but these large animals need a lot of it, as much as 160 grams every day! Thus these giant animals are happy to find as much salt as possible.

On the slopes of Mount Elgon, their wishes can be fulfilled. Sometimes elephants manage to find the salt on the land surface but the best finds are in the caves.

It seems, at first elephants were reaching for the salty cliffs in the hollows behind the waterfalls. As they consumed the salty rock, hollows became larger and larger, and gradually whole caves were carved by the tusks of elephants!

Research shows that indeed – these powerful animals were chipping the rock pieces from the cave wall with their tusks. As pieces of lava fell on the floor, elephants chewed these pieces as delicious candies. Thus over the time of some 8,500 – 12,000 years elephants created the current cave.

Elephants were not alone here – other animals, such as bushbuck also came to “mine the salt” here. Bushbuck also could chip off smaller pieces of the rock. Other animals had to be satisfied with remnants left after elephants.

Dangers in the darkness

As the cave was extended, elephants had to walk through complete darkness to reach the salt – and this became risky. The situation was used by leopards and hyenas – these predators hid in the darkness and waited for smaller and weaker animals to come. Quite a few young elephants, buffaloes, and bushbucks perished in the cave.

There were other dangers too. As the cave room is extended, the ceiling of the extensive room collapses under its own weight. After all, elephants do not care about the structural strength of the cave too much and just dig it wider and wider. In 1982 in Kitum Cave elephants caused one such collapse and at least one elephant died.

But the worst happened in the 1960ies – 1980ies. Poachers discovered the habits of local elephants, hid at the entrance, and ambushed all the elephants approaching the caves. The population of local elephants decreased from 1200 to a mere 100.

Part of the local elephants decided to quit and are avoiding the caves up to this day. Other elephants learned to come silently in the night – and sometimes visitors manage to see them while hiding in the caves through the night.

With the development of tourism and nature conservation, poachers are less active. After all, tourism brings a steady income now. Another danger though comes from the increasing number of people in Kenya and encroachment of agriculture on the forest – thus elephants have less forest left.

The caves at Mount Elgon seem to be the only caves in the world made and visited by the elephants on a regular basis and elephants are transferring the knowledge about the caves from one generation to the next.

Size of caves

The best known – Kitum Cave – is up to 165 m long and up to 60 m wide, with a comparatively low ceiling. The cave consists of two large, rounded chambers. Elephants are entering the largest chamber and go deep inside, reaching the furthest corner – the fresh “salt mine”. Humans have also played some role in the development of these caves – until the 1960ies the salt was removed with pick-axes and salty rocks were used for the cattle.

There are four more “elephant” caves nearby – the largest is the impressive Mackingeny cave, 250 m long. This and Chepnyalil cave (26 m) also are available to the visitors of the park. Two more caves are Ngwarisha cave (150 m, here live around 100,000 bats) and the small Kiptoro cave (10 m).

All five caves have waterfalls that fall over their entrances. Most likely there are some more similar caves in this area.

The deadly Marburg virus and bats

The story about Kitum Cave does not end here. There is one more, gruesome story about this cave.

Marburg virus disease

In 1980 one French visitor after the visit to this cave became ill and soon died from a hemorrhagic fever. His doctor – Shem Musoke – also became ill but survived.

In 1987 another visitor of the cave – 15 years old Danish boy – became ill and died with similar symptoms.

An expedition of the US Army Medical Research Institute of Infectious Disease tried to find the source of the infection soon after but had no success.

This deadly illness was Marburg virus disease. In the first case, it was caused by the Marburg virus, in the second – by the similar Ravn virus. This illness is almost always deadly. 81% of patients do not survive, thus it is more dangerous than Ebola virus disease.

Only in 2007 the research in other caves – mines in Gabon and Uganda – gave some results. Turns out, the Egyptian fruit bats (Rousettus aegyptiacus) are to blame – these small, noisy bats sometimes carry this disease although it is still not clear where bats get these viruses. It seems the illness might be spread by the dust of bat guano.

Since the 1980ies thousands of people have entered the cave without any health problems – but no one can feel sure in the future.

Bats

In all five caves Egyptian fruit bats, as well as other bats species (such as horseshoe bats Miniopterus schreibersi) definitely are present. In some caves, bat colonies are very large – with tens of thousands of these small animals. This huge mass of bats warms up the cool air of caves, they create a thick and pungent layer of guano.

Countless bed bugs live here – usually feasting on bats but upon a possibility attacking everyone who enters this small realm.

Legendary caves

Local people knew about these “elephant caves” for centuries. White people learned about them in the 19th century. It might be that H. Rider Haggard’s novel “King Solomon’s Mine” (1885) was partly inspired by this phenomenon of nature. These caves were described also by Joseph Thompson in the book “Through Masai Land” (1985). Thompson could not figure out whether these caves were made by human or natural activity. Some even considered that the marks on the walls were created by the ancient Egyptians mining the diamonds here.

Only in 1982 there was concluded that at least the Kitum cave to a large extent is made by elephants (Redmond, 1992).

Now, in spite of all the real and imaginary dangers, Kitum cave and other “elephant caves” nearby are popular tourist destinations.

References

1. Joyce Lundberg, Donald Mcfarlane, Mount Elgon’s ‘elephant caves’, SWARA, October – December 2007.
2. Joyce Lundberg, Donald A. McFarlane, Microclimate and niche constructionism in tropical bat caves: A case study from Mount Elgon, Kenya, The Geological Society of America
   Special Paper 516, 2015
3. Joyce Lundberg, Donald A. McFarlane, Speleogenesis of the Mount Elgon elephant caves, Kenya, Special Paper of the Geological Society of America, January 2006, DOI: 10.1130/2006.2404(06)

Kitum Cave is included in the following list:

Geological history

Some 7 million years ago an enormous volcano rose from the 2 kilometers deep Tasman Sea and through gargantuan eruptions created a large island.

As time went by, the island was populated by plants and animals. Island is far from other continents and islands – thus the life here developed on its own and one after another there appeared unique plants and animals. At the same time, waves eroded it step by step.

Now only some 0,25% of the original island remains above the sea – contemporary Lord Howe Island is only 11 by 2 km large. Nevertheless, this is a gorgeous island with impressive hills. The highest summits on this small island are Mount Gower (875 m) and Mount Lidgbird (777 m) – both in the southern part of the island.

Erosion of the island continues and it will disappear under the waves over the next 200 thousand years.

Human history

It seems, Polynesians did not find this island. Europeans for the first time saw the island in 1788 – the island was named after the admiral of the British fleet Richard Howe. In 1830ies was founded small village and villagers released pigs, cats, and quite a few other invasive species which later created much damage to the local ecosystem.

The unique value of the local ecosystem was recognized early – already in 1878 here was declared a Forest Reserve and tourism started to develop in the 1880ies. One of the unique plants brought good income to the islanders – local Kentia palm (Howea forsteriana) turned out to be a much-desired house plant that adorned (and still adorns) the best palaces and hotels in faraway Great Britain and other countries of the world.

Lord Howe Island was one of the early UNESCO World Heritage monuments – it was included in the list already in 1982. Here are ongoing also impressive activities to eradicate invasive animals and plants – slowly, step by step humans are succeeding.

Tourism is limited too – additionally to some 350 local inhabitants at one time here may come up to 400 visitors. This is an exclusive and gorgeous destination, in many aspects without analogs in the world.

The small paradise

Few islands in the world are as beautiful as Lord Howe Island. The incredibly blue sea and the emerald-green island with its steep mountains represent the southern seas at their best. Best preserved natural forests grow in the hills to the south and to the north from the village – on both ends of the island. These mounts are covered with lush vegetation – unique temperate cloud forest and palm forest. Especially impressive is the cloud forest around the summit of Mount Gower – while most of the island often is basking in the sunshine, this forest for most time is covered with a cloud.

There are also numerous caves on the island – some quite long, as well some spectacular waterfalls which form after the rain. Admiralty Island has a natural arch – “Arcade”.

Visitors happily are taking the enchanting (and strenuous!) walks in the hills, diving in the most southerly coral reef of the world (yes, one more peculiarity of Lord Howe Island!), enjoying the fearless and amusing birds, and taking incredibly tasty meals.

But some people feel here even more excited – those who have a somewhat deeper interest in biology. Judge yourselves: for example, here grow 241 species of plants. 113 of these plants are found only here and nowhere else in the world! Or… here live more than 1600 species of insects and nearly 1000 of them – again, only here! Sealife is no less impressive: divers can observe more than 500 fish species and 90 coral species – many of them unique.

Some specialties of Lord Howe Island

• Kentia palm (Howea belmoreana) and also Howea forsteriana. The beautiful kentia palm is popular indoor plant around the world – but in nature it grows only here. Growing of these plants is one of the main business activities on the island next to tourism.
• Lord Howe Island Phasmid (Dryococelus australis) – world’s largest stick insect which was extinct on the main island by 1920ies due to rats and mice. Earlier it was very common – fishermen even used them as baits for fish. It was rediscovered on Ball’s Pyramid – another spectacular cliff 24 km to the south-east from the main island in February 2001. There were only 24 live insects remaining in one bush but since 2009 the species is reintroduced on Lord Howe Island.
• Lord Howe Island white eye (Zosterops tephropleura) – small bird, eating garden fruits and insects;
• Lord Howe Woodhen (Gallirallus sylvestris) – flightless bird. It almost went extinct but now its numbers re increasing and reached some 220;
• Metrosideros nervulosa and Metrosideros sclerocarpa – called also mountain roses. Beautiful shrubs with bright colored flowers;
• Lord Howe Island skink (Oligosoma lichenigera) and Lord Howe Island gecko (Christinus guentheri) – small lizards, both found also on Norfolk Island;
• Lord Howe Island placostylus (Placostylus bivaricosus) – enormous land snail, with up to 7 cm long shell;
• Lord Howe Island stag beetle (Lamprima insularis) – glittering green beetle, some 2 cm long;
• Moorei orchid (Dendrobium moorei) – orchid with white flowers.

A famous peculiarity of the island is its glowing mushrooms, mainly Mycena chlorophanos and Omphalotus nidiformis which may glow for several days after they are picked. These mushrooms emit enough light to allow them to read in the night next to them. Glowing mushrooms appear after heavy rains and their glow is regulated – e.g. they “switch on” the glow when it is dark. These mushrooms are not unique to the Lord Howe Island but here they seem to be more common – or just closer to the eye of curious visitors.

References

1. Australian Government, Department of the Environment and Energy. World Heritage Places – Lord Howe Island Group. Accessed on 25th September 2018.
2. Lord Howe Island Museum. Accessed in 29th October 2018.
3. S. J. Paramonov. Lord Howe Island, A Riddle of the Pacific, Part III. PACIFIC SCIENCE, Vol. XVII, July 1963.

Lord Howe Island is included in the following article:

Atoll of Aldabra

Aldabra is the second-largest atoll in the world and the largest raised coral atoll. Raised atolls have been raised somewhat higher above the water by tectonic forces than the common atolls. This allows for the plants and land animals to survive even the fiercest storms and sometimes unusual, unique ecosystems develop on such atolls. One such example is Henderson Island in Pacific with its unique tropical forest but Aldabra is even more unusual.

Aldabra is comparatively old (for coral atolls) – some 135 thousand years. Over time it rose and descended below the sea level several times and now it rises up to 8 m above the sea. It consists of four large islands, numerous smaller ones, and a shallow lagoon in the middle. Atoll is 34 km long and up to 13 km wide. Total land area here is 155.4 km². This large island system is almost non-walkable, with very rugged relief and thick plant cover.

As Aldabra is well isolated (420 km to the nearest island), fairly large and there is almost no human influence, here has evolved pristine and unusual ecosystem with numerous unique (endemic) species of plants and animals. This is a refuge for more than 400 endemic species and subspecies of plants and animals.

Here are no sources of freshwater and the island is hard to access. Thus Aldabra has not been inhabited by numerous people and its ecosystem is nearly intact. Atoll was well known to medieval Arab seafarers and the name given by Arabs was accepted (with some changes) by the Europeans as well. At the end of the 19th century here was established a short-lived colony but almost nothing remains of it today. Currently, some structures are located in Picard Island (one of Aldabra islands), where some 12 scientists and wardens are living.

Tourism here is heavily controlled and limited. On average here come some 900 tourists per year, but a vast majority of the island is not accessible to them.

Unique animals and plants

The ecosystem of Aldabra is among the most important ones in the world for the studies of the evolution of life.

Giant tortoises

In Aldabra live some 100,000 or even 150,000 giant tortoises – estimates are different. This is the largest population of tortoises in the world. This is also the only land ecosystem where tortoises are dominating – these calm and slow reptiles here are at the top of the food chain even if they are strictly herbivorous.

Not always it was like this – in the Late Pleistocene on the island lived also local species of horned crocodile – Aldabrachampsus dilophus – but now it is extinct. It is highly possible that later here lived also larger crocodiles – there have been found damaged bones of these large tortoises and the small Aldabrachampsus could not inflict such damage.

In newer times the much more dangerous enemy has been humans. Sailors were happy to collect these slow animals and by the early 20th century tortoises were nearly extinct. Only after World War II, the island got a more strict protection regime but by this time in Aldabra were introduced several invasive animals – goats, cats, rats, and some others. They eliminated the food base of tortoises and also endangered the small, young tortoises. Now goats have been eradicated, cats have been removed from several islands but all the time new introductions are looming.

The Aldabra giant tortoise (Aldabrachelys gigantea) is the second-largest species of terrestrial tortoises – just a bit smaller than some Galápagos tortoises, such as Chelonoidis porteri. The medium length of the shell of the Aldabra giant tortoise is 105 cm and the weight of adults is up to 350 kg.

These giant reptiles eat grass and shrubs and even algae in the pools. Per square kilometer here live some 600 – 700 giant tortoises – a lot more animal biomass than even in the richest East African savanna. Nevertheless, the rich ecosystem of Aldabra is able to sustain them. The grazing by tortoises has even changed the local ecosystem and in many places has developed so-called tortoise turf, where dwarfed local plants grow.

In earlier times similar giant tortoises lived on many other islands of the Indian Ocean, including Madagascar. Now they remain only on Aldabra and have been introduced to some other Seychelles.

Other animals

Aldabra is important not only for the giant tortoises – but this is a very important feeding ground also for green sea turtles (Chelonia mydas) and hawksbill sea turtles (Eretmochelys imbricata).

Here live also three endemic species of bats…

• Aldabra flying fox (Pteropus aldabrensis);
• Little Free-tailed Bat (Chaerephon pusilla or pumila);
• Paratriaenops pauliani

…and two – three endemic species of birds…

• Aldabra Brush Warbler (Nesillas aldabrana) – not seen since 1983 and considered to be extinct;
• Aldabra Drongo (Dicrurus aldabranus);
• Aldabra foudy (Foudia aldabrana).

…as well as 11 endemic subspecies of birds, including the flightless “version” of White-throated Rail (Dryolimnas cuvieri aldabranus), the only remaining flightless bird in the western part of Indian Ocean.

Here is located the second largest frigatebird colony in the world, one of two oceanic colonies of flamingos.

On the atoll are known more than 10000 species of insects and many among them are met only here.

Plants

On the atoll grow at least 273 species of plants, including up to 42 endemic species. Some of the endemics are:

• Allophylus aldabricus – small tree or shrub
• Aloe aldabrensis
• Tropicbird orchid (Angraecum seychellarum)
• Jasminum aldabrense
• Aldabra lily (Lomatophyllum aldebrense)
• Pandanus aldabrensis

and many others.

Besides the outstanding scientific importance, Aldabra Atoll is simply gorgeous. Nature here has created a harmonious, colorful, and lively spectacle.

References

1. UNESCO World Heritage List. Aldabra Atoll. Accessed on 23 September 2018.
2. Terrestrial biozones. Aldabran Endemic Plants. Accessed on 24th September 2018.

Aldabra Atoll is included in the following article:

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

Volcano

Kelimutu is a dormant stratovolcano – a steep-sided volcano with a crater on its top. Around the summit of the 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 the Kelimutu crater lakes has its own color, and this color changes over time irrespective of the changes in the other two lakes.

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 the 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 fluctuate for each of the lakes separately. Thus, thanks to complex chemical processes of oxidation and reduction the color of lakes is changing over time. For example, in January – November 2016 the color changed six times.

The 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 that always have different colors. There is no other volcano on Earth with similar phenomena.

History

Locals, of course, have known about these lakes since antiquity but the 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, a 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 a certain equilibrium between the interests of nature conservation, local people, and an increasing stream of tourists. Tourists now love to visit the summit of Kelimutu at sunrise and enjoy the unique view of three diversely colored lakes basking in the lush light of the rising Sun.

References

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 are included in the following article: