Erta Ale volcanic activity : 2017 overview and June update
Introduction and geological setting
The large volcano complex of Erta Ale is situated in the Danakil depression (NE Ethiopia). This NW-SE trending upper portion of the East African Rift valley represents the breaking up of the African continent with the ascent of basaltic magmas that push apart both plates and created a volcanic line of shield volcanoes between the salt lakes of Assale and Afdera. Amongst these dormant volcanoes Erta Ale is the active one and world famous for its persistent lava lake that has been active during most of the past decades since it was first discovered in the 1960s.
Google Earth images showing the location of the Danakil depression within the Horn of Africa and a close-up of the Erta Ale volcanic chain.
In historic times volcanic activity took place within the summit caldera
Although only 613 m high, Erta Ale has a large ca 40 km diameter base and the very gentle slopes typical of a shield volcano. Its summit is truncated by an elliptical 1700 x 600 m wide caldera which contains thick layers of old lava flows and several larger and smaller pit craters. Up to late January 2017, volcanic activity was concentrated in two such pit craters within the large summit caldera. The South crater is the home of a continuously active lava lake which surface level rose and fell throughout the years, alternating between overflowing the caldera floor and being 10s of m below it. The North crater on the other hand showed only intermittent activity from a large central hornito that continuously degassed but from time to time also spit out some red hot lava.
Observing the lava lake in the South crater of the summit caldera in February 2008 (image: Tom Pfeiffer)
The North crater of the summit caldera with its degassing central hornito in November 2015 (image: Ingrid Smet)
Red glow from the simultaneously active hornito in the North crater (front) and lava lake in the South crater (back) in February 2009 (image: Tom Pfeiffer)
Late January 2017: New fissure eruption on Erta Ale´s SE flank and partial collapse of the North and South craters
The November-December 2016 phase of high activity with the South crater lava lake regularly overflowing continued well into 2017 and culminated into a never before witnessed 3-day spectacle of intense overflowing of the perched lava lake which covered large parts of the summit caldera floor in several meters of fresh pahoehoe lava. The summit caldera could however not cope with the large influx of molten magma from deep below Erta Ale, and around 20 January 2017 a new fissure opened up on the volcano´s flank, some 3 km southeast of the summit and within a much older and larger collapse caldera. This new eruption site allowed for a quick outflow of the large volumes of ascending magmas, and a new lava field with multiple pahoehoe flows and lava lakes was quickly constructed. As a result, the lava did no longer have to find a way out through the higher located South crater and hence quickly drained from the summit caldera, leaving large cavities below both the North and South craters which then partially collapsed in the days after 21 January 2017.
A unique photograph showing how mid January 2017 the South crater lava lake was spilling over its rim, creating many new lava flows that cover the summit caldera floor (image: Paul Reichert)
Volcanic activity at Erta Ale : February to June 2017
Under the guidance of Ethiopian geologist and VolcanoDiscovery tour guide Enku Mulugeta a small group of travelers undertook a VolcanoAdventures expedition to the Danakil
in the first half of February 2017
. They reported back that within the summit caldera the entire hornito of the north crater had collapsed and that the lava lake in the south crater was now ca. 80-100 m below the caldera floor level. As a few km to the SE the eruption from the new fissure on Erta Ale´s flank was still going on, they repeatedly hiked there to observe and photograph the sizable new lava field that had quickly formed and which contained numerous pahoehoe lava flows, actively spattering hornitos and a large lava lake. During the following months activity remained high both at the new fissure eruption site and at Erta Ale´s summit caldera where the lava lake in the South crater gradually rose up to about 50 m below the caldera floor.
Based on his own field observations and discussions with his colleagues at the Addis Ababa University, Ethiopian geologist and VolcanoDiscovery tour guide Enku Mulugetu reports: “The volcanic activity in the South pit crater of the summit caldera increased remarkably from mid April to early June
. The level of the lava lake is now only 40 m below the crater rim and it occasionally shows vigorous fountaining up to 25 m high. There are now also two 4-7 m high hornitos within the eastern wall of the South crater whose diameter widened from ca 75 m to 200 m due to the large collapse at the end of January 2017. By now the caldera floor around the south crater is again stable and accessible so that one can once again go to the very edge of the South crater to observe the lava lake´s activity below." One exceptional new phenomenon observed at the South crater is the rise and fall of the lava lake´s level, from ca 40 m to 50 m below the caldera floor. According to Enku this process repeats itself ca every 30 minutes, with a number of lava tubes at the base of the South crater providing the necessary plumbing system for this draining and rapid refilling of the active lava lake.
Video of the South crater lava lake´s draining and refilling cycle:
February 2017 photograph of a large lava lake that formed at the new flank eruption site SE of the summit caldera (image: Stefan Tommasini)
Daytime view of a part of the active large new lava field that formed from the fissure eruption ca 3 km SE of Erta Ale´s summit caldera (image: Stefan Tommasini, February 2017)
Once the new fissure eruption had started, a large new lava field quickly formed on Erta Ale´s SE flank and continued to grow through the creation of many pahoehoe lava flows (image: Stefan Tommasini, February 2017)
June 2017: Significant increase in eruptive activity at the new SE flank lava field
The new flank eruption continued to be active throughout the first half of 2017 and greatly intensified in early June when overflowing of the ca 200 m diameter lava lake created new pahoehoe lava flows both in northeasterly and southwesterly direction. Enku Mulugetu writes: “Satellite images confirm that there has been a continuous outpour of lava from the new fissure eruption which seems to be building a new shield with different active vents from where pahoehoe lava flows, but not much fountaining or degassing occurs. Although it is at present still not possible to get close to the new lava lake in this area due to the fresh hot lava surrounding it, we can venture up to the rim of the old caldera which is some 500 m away from the most active vents.” ESA/Copernicus Sentinel 2 satellite images of the Erta Ale volcanic range compiled on the volcano blog ´Culture Volcan´
indeed show that between 8 and 18 June 2017 the SE fissure lava field drastically increased, with the most active lava flow growing from a ca 950 m to about 3200 m length in the timespan of 10 days!
“For most natural phenomena, a lifetime is too short to see their change” Enku Mulugetu muses, “but in East Africa´s Afar Triangle we have now witnessed some dramatic volcanic activity in a matter of a few months… So I am very much looking forward to enjoy each minute of the upcoming Danakil expeditions
where I have multiple days to explore together with the travelers the changing volcanic activity at both the new and old lava lakes and eruption sites of Erta Ale!”
ESA/Copernicus Sentinel 2 satellite images showing the impressive growth of the new SE flank lava field between 8 and 18 June 2017 (image collection and annotations: Culture Vulcan)
Expeditions to Erta Ale
14 days expedition to Erta Ale volcano and Dallol hydrothermal field (Danakil desert, Ethiopia)
14 days / 13 nights - ModeratePrice $ 4530
no scheduled dates at present