Looking at Dallol for the first time, you would think you were on a movie set for the next big sci-fi blockbuster, or on a different planet entirely. This unique habitat has been named the hottest place on earth, with an average daily temperature exceeding 38°C. Not only is it one of the hottest places on the planet, it is also one of the most geologically active. It comprises of a diverse range of features including shield volcanoes, brine pools, acidic hot springs, geysers spewing out toxic vapour, gas emitting fumaroles, and phosphorescent green sulphur congregations. It is a bubbling, toxic, molten expanse of land unlike any else found on earth.

An image showing an ariel view of Dallol, Ethiopia. (Photo credit: Public domain backwallpapers.com
An image showing an ariel view of Dallol, Ethiopia. Photo credit: Public domain backwallpapers.com


A diagram showing the spreading movement of the 3 tectonic plates at the Afar Triple junction. Credit: Google Earth

Dallol is a hydrothermal field located in the Danakil depression found north east of the Erta Ale Volcano Range in Ethiopia. Dallol covers an area of 1.150 km2 and is one of the lowest points on earth, found 125 metres below sea level. The Danakil depression, also known as the Afar depression, lies far north within the Great Rift Valley between 3 spreading tectonic plates: Arabian Plate, African plate (Nubian) and African Plate (Somalian). As can been seen from the diagram to the right, the ground between these three plates are spreading in 3 directions at a slow rate, resulting in the earth’s crust becoming thinner, allowing the heat to rise up and form cracks. This forms volcanoes, hot springs and the many other geological features that can be found here resulting in this natural phenomena. A rift valley is where the Earth’s tectonic plates move apart, creating new crust. These deep rift valleys are separating at a rate of 1-2cm per year.

Diagram showing the creation of a Maar (Photocredit: USGS/Geology.com)
Image showing the creation of a Maar. When water pressure over underlying hot rock becomes too much, a phreatic explosion occurs Photocredit: USGS/Geology.com

Although Dallol is branded as a volcano, it is not a true volcano. The Danakil depression is located parallel to the Red sea, salt is drawn from the Red sea beneath the surface and is intruded through basaltic magma. Additionally, salt water has also entered the Danakil depression and flooded the divide between the Danakil basin and Red sea, due to its low relief. This sea water meets overheated rocks turning into vapour, when the vapour reaches a critical pressure level, the salt layer is blown away in a phreatic explosion, leaving behind a maar, a broad and low relief explosive volcanic crater. The most recent account of an eruption occurred in 1926, when am explosion created a maar 30 metres wide, this was the last significant event to happen at Dallol.  At 48 metres below sea level, Dallol is the lowest known subaerial volcano in the world.

The Landscape

An image showing the different structures found in Dallol as a result of rapid evaportion photocredit: pinterest.com

The complex interactions between salt solutions and recrystallization processes, driven by the hydrothermal field activity and rapid evaporation are to thank for the diverse structures found in Dallol. The hot magma beneath the surface heats ground water flowing in from areas such as the Red sea, leaving behind a hyper-saline brine. As the brine is evaporated, salt deposits are left behind forming structures on the floor of the craters, giving dallol its extra terrestrial terrain and unique topography. These salt deposits include significantly formed bodies of potash in the form of Slyvite (KCL), Carnallite (MgCl2-KCl-6H2O) and Kainite (MgSO4-KCl-11/4H20).

A video showing the unearthly scenery of Dallol, Ethiopia.

Most colourful place on earth?

Dallol's toxic mixture of sals and sulphur creates its unique colourful landscape. (Photocredit: something-interesting.com)
Dallol’s toxic cocktail of salts and sulphur creates its unique colourful landscape. Photocredit: something-interesting.com

What makes Dallol so unique is its visually striking landscape, boasting more colours than a bag of skittles. The combination of vibrant yellows, oranges, reds, greens and purples (on occasion) are caused by the mixing of minerals, salts, sulfurs and iron at the site. The Halite, Sylvite, Carnallite and Kainite salts found here are relatively colour-less or white, however the addition of ions within the salt crystals are responsible for the vibrant colours, making dallol completely visually different to the rest of the Danakil depression. The characteristic white, yellow and red colours in Dallol are a result of high Sulphur and Potassium concentrations.

The sulphur particles present in the sediment heat up occasionally and erupt in spectacular luminous violet plumes. Photo credit: Olivier Grunewald
The sulphur particles present in the sediment heat up occasionally and erupt in spectacular luminous violet plumes. Photo credit: Olivier Grunewald

 Life inside an inferno

With the acidic brine pools exhibiting a pH of <1 in the waters and escaping gas, it is hard to believe that living organisms can be found living in these habitats. However surprisingly, is has been discovered that Dallol can sustain some life forms. In January 2016, a group of scientists made up of geologists, microbiologists, and crystallographers came together for the first time to look for traces of life at Dallol. The team, lead by senior researcher Purificación López-García from ESE, studied the site for 2 weeks taking as many samples as possible from the area. Their preliminary findings were astonishing, showing that Dallol is twice as saline as the Dead Sea and the fissures of the geysers exceeded 100°C.

Scientists collecting samples in the brine pools of Dallol (in this picture, Purificación López-García and Ludwig Jardillier) Photo credit:
Scientists collecting samples in the brine pools of Dallol (in this picture, Purificación López-García and Ludwig Jardillier) Photo credit: Olivier Grunewald.

Once back at the labs, the samples were analysed using electron microscopes. Single celled Archaea were found in some of the samples, many have which had also been observed at deep sea hydrothermal vents. These organisms were small, suggesting their adaption to the extreme environment with limited resources. The team of scientists on this study believe that Dallol could give an insight into the extremity of environments found on earth over 3.5 billion years ago, and that life found here could resemble the origins of life on earth. López-García commented: “Dallol is in fact a sort of open-sky scientific model that provides insight into how our planet functioned during an age when geology still prevailed over biology”.

Extremophiles including Halophile Algae have also been found living in the pools, contributing to the psychedelic fluorescent green colouration.

Hot spring found in Dallol, Ethiopia. Halophile Algae and Sulphur gives the pool its vibrant green colour. Photograph by George Steinmetz

An insight into life on other planets?

As well as giving an insight into the origins of life on earth, microbes like this are of special interest to Astrobiologists, as research on terrestrial extreme hydrothermal habitats may assist in understanding how to recognize life on Mars. They could help to explain how extraterrestrial life could arise. In conclusion, Dallol gives us a unique insight into what happens when a combination of geological and physical features meet in one place, with more research their habitable environments may reveal evidence for the origins of life and how life forms could potentially begin on other planets.


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