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Erta Ale Volcano and Danakil Desert

Lothar Fritsch, Jan. 2003

Report of an Expedition Nov.-Dec. 2002

From November, 23 to December 15, an expedition group led by VEI Expeditions (1) traveled the Danakil desert in norteastern Ethiopia. The goal was to reach and explore the Erta Ale volcano and surrounding volcanic structures of the Danakil. This report summarizes findings of the expedition, including lava lake observations, recent changes at the crater, earthquakes, temperatures and a newly observed hazard to volcanologists at Erta Ale.

Before Reading

All photographs are linked to larger images when you click on them. This also holds for the graphs of the caldera.
Footnotes are of the format (x) where x is a number, hyperlinked to the footnote text. The footnote text is at the end of the document,
References to GPS coordinates are noted like (ERTFUM), where the characters refer to the coordinates in table 1.
All photographs and other materials are (c) Lothar Fritsch, 2002,2004, unless explicitly stated otherwise.

Erta Ale Caldera

Measurements of landmarks and the shapes of the caldera and crater rims were made using a 12-channel GPS receiver. GPS receiption was excellent due to the exposed nature of Erta Ale, where signals are shaded only when the receiver is close to the caldera wall inside the caldera. Figure 1 depicts the caldera shape as measured. Table 1 lists the coordinates of several points of interest inside the caldera.

Please note that the measurement error of the rims is about 15m, shifting the lines to the outside of the caldera and the craters due to the necessary safety distance to be held towards the rims. The points of interest are precise coordinates.

Erta Ale Caldera seen from East Erta Ale Caldera seen from South Erta Ale eastern Caldera rim Erta Ale eastern Caldera rim
Image 1: Aerial caldera view from East. Image 2: Aerial caldera view from South. Image 3: Aerial view of northern caldera end with crater pits. Image 4: Aerial view of eastern caldera wall.

Rocks and Minerals

Pelees Hair at Erta Ale
Image 5: Pélée's Hair is found next to Erta Ale south pit crater.

We found serveal volcanic minerals. First, the basaltic lava flows that proceed from the craters to the southern caldera end provide large varieties of flow patterns and lava tunnels. At the southern end, lava seems to have cooled off enough to brek into large tiles and create a lava field that was nearly impassible.

On the norteastern slope of the central honito (ERTHTO), crystalline sulphur was found. This was also the case at the western rim of the north crater pit, close to the place where the crater rim and the caldera rim join. More sulphur was found in the soil at the emergency exit location (ERTAEX) and in the caldera wall just north of the camp (ERTACMP).

Around the south pit, in particular near its northern and northwestern rim, the ground is widely covered with Pélées Hair. Gas eruptions and rock fall into the lava lake constantly caused this mineral to be ejected from the pit by hot air circulation.

On the outside of the caldera rim, strictly northwest from the fumarole field position (ERTFUM), fumaroles are found. Grass lives off the water vapors, while eggshell-like gypsum structures grow in a large field around the fumarole openings.

Erta Ale Caldera Sketch according to GPS measurements
Figure 1: Erta Ale Caldera Sketch according to GPS measurements.
Blue: Crater and Caldera Rims; Black: Point of Interest.
Coordinates can be found in Table 1.
Description Latitude
ERTA Erta Ale coordinates from literature 13.60000 40.67000 663.9
ERTAEX Convenient caldera emergency exit 13.60492 40.65972 579.6
ERTCMP Camp location 13.60249 40.66172 549.8
ERTFUM Fumarole field 13.60517 40.66187 588.7
ERTHAK Location of climbing fixture 13.60402 40.66401 563.0
ERTHEL Helicopter landing area 13.60449 40.66511 566.1
ERTHNN Hornito on northern caldera rim 13.60829 40.66222 594.9
ERTHR2 Hornito north of south pit. covered with lava 13.60417 40.66434 573.3
ERTHTO Large hornito (summit) south of south pit 13.60195 40.66387 591.8
ERTMP1 Landmark on rock 13.60035 40.66174 583.6
ERTNRD Edge of north crater pit 13.60534 40.66168 594.9
ERTSEE Edge od south crater pit 13.60341 40.66462 582.0
Table 1: Coordinates of the Erta Ale Caldera.

South Crater Pit and Lava Lake

South crater pit
Image 6: South crater with terrace.

The south crater was of ellipsoid shape of about 160m in east-west orientation and about 130m in north-south orientation. Inside the crater, about 1/2 of the area were covered by basalt rock which built a terrace about 45 meters below the crater rim. The terrace was located on the eastern crater rim, while the remaining 1/2 of the area was taken up by a lava lake. The lava lake surface was about 90m below the western rim of the south pit.

Almost no talus was found on the terrace. In comparison with the crater described in (2) and (3), the lava lake must have risen up to the present terrace altitude since early 2002, when the last report found the terrace at about 70m below the rim, and widely covered with talus.

Crater Rim and Walls

The surface near the crater rim was broken by cracks of different width that ran in concentric circles around the crater pit. Many parts of the edge were hanging over empty space.

When descending into the pit, the crater walls were found to be very instable material from small gravel up to large boulders. material fell out of the wall by itself, or by simply being touched by a rope. A climber set off large boulders with his feet.

We considered a prolonged stay near the pit's edge a considerable risk and thus recommend serious safety measures.

Lava Lake

Activity, gas bubbles, patterns...

Erta Ale lava lake Erta Ale lava lake Erta Ale lava lake Erta Ale lava lake pattern
Image 7: Erta Ale lava lake. Image 8: Erta Ale lava lake closeup. Image 9: Erta Ale lava lake at night. Image 10: Erta Ale lava lake pattern with gas eruption.

Rock Falls and Wall Collapses

Rock avalanch hits lava lake at night (animation)
Image 11: An avalanche of rocks penetrates the lava lake at nighttime
(click image to see animated image series).

Rockfall was observed on all days. Generally, material fell out of the south crater pit wall in two ways:

Particularly the avalances seemed to destabilize the crater rim. We observed an increasing frequency of avalanches towards the end of our stay. On Dec. 6, a series of three large avalanches detached from the northwestern wall at about 8:00 local time while two team members were in the crater to retrieve a lava sample. They were evacuated from the pit with no harm, but also with no lava sample.

Three observations were made after avalanches hit the lava lake:

Fumarole Temperatures

Measurements were made to assess the temperatures of the funaroles in the fumarole field (ERTFUM).

Eartquake Activity

Several earthquakes were noticed during the stay. No seismic equipment was present, but nontheless five seismic events were well observed. On Dec. 4, 2002, a short trembling was noticed by group members in the early evening hours. The following day, on Dec. 5, at 12:40 and 13:12 local time, at both times a series of two seismic events of each 1-2 second of duration and a several-second break was noticed through ground trembling and noise. No rapid change on the lava lake was noticed at that time.

Weather Conditions


Clear sky, Dec. 3 clouds, temp.


SE winds up the caldera, N at Dec. 3

Animal Life

During our stay, several species of animals were encountered, some of which we did not expect in an hostile environment as the Erta Ale Caldera. We observed:

  1. Vulkan Expeditionen International, Christoph Weber, http://vulkanexpeditioneninternational.de/
  2. F. Pothé, E. Pradal, F. Chizat: Erta Ale le lac de lave déborde sur la terasse; in Bulletin No.23 de la Société de Volcanologie Genève, 2002
  3. P. Vetsch, F. Crouchon: Quelques observations supplémentaires; in Bulletin No.23 de la Société de Volcanologie Genève, 2002

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