Ethiopia, February 2011

I attended the Regional Conference of the International Association of Geomorphologists, held in Addis Ababa in February 2011. In addition to a mid-conference field visit to the Blue Nile Gorge, I went on a preconference field trip to the Rift Valley. The highlight of the trip was an informal expedition to the Danikil Depression in the Afar region in the North of Ethiopia with fellow planetary scientists Rosaly Lopes, Jani Radebaugh and Serina Diniega and some friends of Rosaly. Our main goal was the Erta Ale volcano, ostensibly as an Io analog. Photos (c) R. Lorenz, unless otherwise noted.

010_P2180231 Rosaly, and Lucy, a 3.2 million year old homind skeleton, discovered in the Afar depression, in the National Museum in Addis. 020_P2150152 Melka Kunture, a site 50km from Addis Ababa, where a 0.8 million year old 'factory' for stone tools, and this butchering area, were discovered. 030_P2150158 These stelae, something between obelisks and gravestones (though functionally more like the latter) date to ~1200 AD, although no documentation exists [an irony - this area has the longest human history, yet almost no written history]
050_P2170203 Lake Langano, one of several lakes in the Main Ethiopian Rift. I even ventured a swim - this lake (unlike many bodies of standing water in Africa) is free of the bilharzia parasite. Only about 9m deep, the lake water is usually tea-colored due to suspended clay. 055_P2170212 The rift valley lakes were deeper and joined into a single lake only 10,000 years ago or so. Beautiful lamellar lake sediments attest to this, and the presence of snail shells in the sediment indicate that they were deposited underwater, unlike the widespread ignimbrite deposits from the volcanic activity in the Rift. 060_P1010333 The Blue Nile Gorge offers a remarkable 1300m sequence from recent lava flows down to the preCambrian basement: it is in fact about 80% as deep as the Grand Canyon. Morphologically it was slightly different (more intermediate slopes, whereas the Grand Canyon seemed more chiseled). Unfortunately slightly hazy (as was the trip to the Rift - was hard to appreciate the full scale of it).
070_P2200253 The Blue Nile sequence is capped by lavas - the columnar basalt seemed striking next to the cactus tree, with faintly similar morphology. Like Addis Ababa, the altitude here was about 2000m, so temperatures were comfortable. 080_ The floor of the valley was much warmer. The river has a gravel bed (somewhat unlike the Colorado), presumably due to the considerable (factor of 40) variation in streamflow. 090_P2170223 We also visited the maar volcanic craters that form lakes at Debre Zeit, close to Addis.
100_P2170226 The ashfall deposits here are very comparable with Kilburne Hole, a maar in New Mexico. 110_P1010399 The trip to the Danikil began with a 1-hour propeller flight to Mekele, and a day drive on gravel roads. En route, we encountered the camel train climbing out of the Danikil. 115_P1010761 We had lunch in the small town of Berhaile - the limestone here makes a good building material, a solid contrast to the sticks used more generally. The inverted carcass of an armored personnel carrier (a Russian-built BTR-60, if I am not mistaken) may be a vestige of the border conflict with Eritrea (during which Mekele was bombed), but things have been quiet for several years. (photo:Jani)
117_P2230276 I found the satellite TV dish on the stick shack restaurant rather amusing. We had lunch in a similar place nearby - I have eaten goat in restaurants before, but not eaten lunch in restaurants where goats wander in..... 120_P1010606 Another few hours on gravel brought us down close to sea level and the vilalge of Hamad Ela, where we stayed a couple of nights, on straw cots in the open air (even at night it was ~35C). Here is the gang at dinner - at left is Rosaly and Ken Freund, and a french/german group that was on a similar itinerary: at right are Irene and Jim Dorsey, Serina and myself (photo:Jani) 130_P2250442 The drive south from Hamad was cross-country, much of it in this bone-dry clay, which often reduced visibility to nil. Even out in the middle of nowhere, there are huts with people eking out a meagre living with cattle or goats.
140_IMG_0206 We got stuck, high-centered in deep ruts in the clay. While people dug out, I flew my little kite camera to keep myself amused. 142_P2240322 A neat little dunefield could be found abutting the Dodom river. I sit here between the arms of a nice dome-like barchan dune (kitestring in hand). One of the many volcanos in the area is behind me. 145_P2240358 As we approach Erta Ale, the lava deposits begin. We saw many dust devils in this area, perhaps enhanced by the thermal contrast between dust and lava. Volcanic cone in background, looking north towards Eritrea.
150_P2240416 We had lunch and a rest in a small village at the foot of Erta Ale before beginning the ~10km hike up, with Afar 'policemen'/guides. No, those arent water bottles, they're hand grenades. These and the AK47s seemed to be mostly for show - some of these guys were pretty friendly. 160_P2240419 Nice ropey pahoehoe lava. 165_P2240395 Four hours of hot hiking later (Erta Ale's summit is only about 630m) we are enticed by the glowing steam emerging from the crater at about midnight (this picture was actually nearer dawn).
170_ Another 20 minutes of gingerly scrambling over shelly pahoehoe and we are greeted with the spectacle of one of the world's few active lava lakes, about 50m across and 15m deep. One of the most amazing things I've ever seen. See below for video. 180_P2240388 Every so often a bubble of gas would cause a fountain of lava to burst out, part of the crater wall even foundered once. We'd have loved to stay longer, but after an hour the guys with guns wanted us to climb back up to the rim to go to sleep (there were some small huts to keep out the wind). 190_P2240405 Serina, me and Jani - after 4 short hours of sleep it was time to hike back down, sadly. The floor of the crater is visible behind, most of it covered by a lava flow that formed when the smaller (steaming) lake crater overflowed a few years ago.
200_P1010614 After spending the day hiking down and driving back (didnt get stuck, though had to stop to fix stuck brake calipers) we set off across the salt flats at Dallol. The salt polygons are very reminiscent of Death Valley (although Dallol is much larger) or the Chott El Djerid in Tunisia. 205_P2260474 Climbing up a small rise in the salt flats we find these curious salt textures. 210_CIMG0827 And then a bit further - this! A riot of sulphurous colour in hydrothermal deposits (as if Yellowstone national park were embedded in a big version of Death Valley). The hues were astounding.
220_ 'Gate' (our always-smiling tour guide), myself, and an Ethiopian soldier. 230_P1010642 Jani, Rosaly (the 'Io gals') and myself. 240_CIMG0906 Some km to the west, we find this bubbling hydrothermal pool. The water here was NASTY (unfortunately I ditched the kite in it). Despite the heat and dry air, this stuff just did not evaporate - must be so laden with salts and acid.
250_CIMG0886 Some neat pillars caused by resistant patches in the upper clay layer preventing solution of the salt. 260_P2230291 Camel trains stretching as far as you can see - staggering. It takes a couple of days for them to get to Mekele. 270_CIMG1031 The camels are for hauling salt, hacked out of the ground by hand. Hot, corrosive work - and probably done much like this for the last 2000 years. Amazing to see - and Adam Smith's division of labor is at work - some guys roughly break up the salt layer, others hack the blocks into a nice uniform size for loading onto the camels.
280CIMG1074 On the way back, we saw the stone-hewn church at Wukro. Lovely cross-bedding. Video of the Lava Lake (44MB MPEG). Hard to hold the camera steady as a billow of sulphur dioxide would get us all coughing...watch for the wave 30 seconds in... and notice the glowing window in the crater wall at right - we have no idea if there was similar undermining beneath our feet....
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