The Earth Story

Lava Lake at Erta Ale Lava lakes are a relatively rare phenomenon; currently only seven are known to exist in the world (an eighth, at Kilauea volcano, drained away in 2018). The lava lake in this photo is located in the summit caldera of Erta Ale volcano in the Erta Ale Range of Ethiopia.

Plume opal These rare pieces have been dribbling out of Ethiopia over the past years, and display amazing patterns of play of colour resembling lava lamps rising through viscous fluid. The cause is simple, there are two generations of opal here. The first transparent matrix generation contained dendritic plume shaped inclusions, which were then replaced by a second generation of precious opal sometime later. Loz Image credit: Opal Auctions.

The Northern Lights opal We often share stunning photos of streamers of charged plasma being excited by the solar wind high above the atmosphere, but here is a beautiful example from the mineral realm, from a nodule mined in the rhyolitic silica rich lavas and welded ashes of Ethiopia. These lavas are part of the endless eruptions that accompany the rifting of a continent, and the birth in the distant future of a new ocean all along the Great African rift valley, stretching from the Mediterranean into the heart of the continent. The photo is stunning enough to mostly speak for itself, what a beaut. Loz Image credit: Opalinda

The oldest Homo fossil

The Great African Rift Valley (along which the continent is being sundered apart by convecting mantle currents or a mantle plume rising from below) was the cradle of the human family, and fossils of our distant ancestors have turned up along much of its length. Ethiopia is famed for hosting the oldest remains of our genus and its ancestors found so far, including the iconic Australopithecine Lucy. The recent discovery of a lower jawbone and five teeth eroding out of a rocky slope turned up some 15 km from the Lucy site, and was dated by several methods as the earliest piece of our genus found so far, at 2.8 million years old (some half million years older than the next in line).

Like Lucy and many other important hominid fossils, it was found in the Afar triangle, the triple junction point where the Nubian, Somalian and newly separated Arabian plates meet, and start drifting apart. Nowadays the area is desertic, but back in our ancestor's time it was open grass and shrub land with tree lined rivers, though the evidence suggests that the area was considerably wetter when the new find walked the Earth than in Lucy's day, some 200,000 years earlier. This may indicate a climatic transition that killed off Australopithecus and promoted the development of the larger brains of the hominids.

Fossil hominids are very rare, and few specimens that date from 2-3 million years back help us fill in some major gaps in the evolutionary line of our species, since the period remains poorly understood since evidence is very scarce. As a scientist put it, you can put the entire collection of our ancestors remains for the whole million years into a shoebox and still have room for the shoes. When Lucy's species died out, two main lineages developed out of it, one of which led to us but no record of the transition period had turned up until now.

The jawbone shares some 'primitive' features with Australopithecus like the shallow chin bone while also having distinctive hominid characteristics, such as thinner teeth, and represents the earliest transitional specimen, right at the beginning of our genus. The remains are too scanty to know whether they are the first known species on our lineage (Homo habilis) or another, so far undescribed species. The site is being explored for further remains, and we'll keep you posted if anything interesting turns up.

Loz

Image credit: Brian Villmoare/PA

http://news.nationalgeographic.com/news/2015/03/150304-homo-habilis-evolution-fossil-jaw-ethiopia-olduvai-gorge/ http://www.theguardian.com/science/2015/mar/04/jaw-bone-discovery-in-ethiopia-is-oldest-ever-human-lineage-remains

http://www.npr.org/2015/03/05/390717001/jaw-fossil-in-ethiopia-likely-oldest-ever-found-in-human-line http://www.nature.com/articles/nature14224.epdf Orignal papers, paywall access:

http://www.sciencemag.org/content/early/2015/03/03/science.aaa1415 http://www.sciencemag.org/content/early/2015/03/03/science.aaa1343

A story in sediment

These pillars of rock are found in the Afar depression in Ethiopia. The story of these rocks may be the first chapter in the story of an ocean.

The Afar Triangle is a corner of Ethiopia that buts up against the Red Sea. The Red Sea itself is a newly formed “ocean”, with two tectonic plates rifting apart and a volcanic spreading center in the center. That spreading center heads south and makes a turn out into the Indian Ocean at the point where it connects to the Afar triangle.

There are several places on earth where several mid-ocean ridge spreading centers come together; called triple junctions by geologists because 3 plates are coming together at a single spot. The Afar depression is developing as though it may become the third edge of a triple junction if East Africa fully rifts away from the continent.

The land in the Afar depression is sinking as the land rifts apart, but it is happening very slowly. These rocks are carbonate and evaporite rocks, formed when the ocean levels were high enough to flood this part of the basin.

One final interesting note: these rocks are in a rift zone formed by land that is sinking down over time, but they’re also oceanic rocks. The fact that these were deposited in an ocean implies that in recent geologic history, sea levels have been high enough to submerge this area. In other words, even though we’re in an interglacial period, at some point in recent geologic history sea levels have been higher than they are today to produce these rocks. At some point in the future, as the land continues to subside from faulting and sea levels rise from the changes humans are imposing on our atmosphere, the sea may again claim this location.

-JBB

Image credit: Achilli Family, CC BY 2.0 http://bit.ly/DallolSalt

Read more: https://eos.org/project-updates/reading-history-afar

The Dallol volcano and the Danakil depression of Ethiopia. Sediments wash into this basin and Dallol is a site of magma intrusion into the sediments - it creates the colorful geothermal system seen in this video.