tag:theconversation.com,2011:/ca/topics/great-rift-valley-2688/articlesGreat Rift Valley – The Conversation2018-11-08T13:37:03Ztag:theconversation.com,2011:article/1063222018-11-08T13:37:03Z2018-11-08T13:37:03ZTracking the hazards – and benefits – of volcanoes in East Africa<figure><img src="https://images.theconversation.com/files/243921/original/file-20181105-83635-4pguwr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The active Erta Ale volcano in the northern Afar region of Ethiopia.</span> <span class="attribution"><span class="source">Mikhail Cheremkin/Shutterstock</span></span></figcaption></figure><p>More than 100 <a href="http://volcano.si.edu">young volcanoes</a> – that have had activity within about 10,000 years – dot the landscape of the East African Rift – an area that runs for more than 3000 kilometres from Djibouti and Eritrea, down through Ethiopia, Kenya, Uganda and Rwanda to the Democratic Republic of Congo and Tanzania. </p>
<p>This is the place where the African continent is slowly <a href="https://theconversation.com/africa-is-splitting-in-two-here-is-why-94056">breaking apart</a> at a speed slower than the rate at which human fingernails grow. Steep escarpments and East Africa’s deep lakes – like Lake Tanganyika – are the result of this slow spread. It would however still take <a href="https://www.youtube.com/watch?v=IVnkfvqwDcM">millions of years</a> before the split occurs. </p>
<p>This process of continental breakup is strongly associated with volcanoes because, as the land splits, <a href="http://ethiopianrift.igg.cnr.it/rift%20valley%20history.htm">molten rock</a> rises into the Earth’s crust. Some of this magma makes it to the surface and forms volcanoes. </p>
<p>Most of East Africa’s volcanoes are currently dormant. But they could erupt in the future. About 25% of Africa’s volcanoes had eruptions <a href="http://volcano.si.edu/">in the last 100 years</a>; therefore it’s very likely that we will encounter new eruptions in the next few decades. </p>
<p>Sometimes there’s very little warning before an eruption, as was the case when <a href="http://volcano.si.edu/volcano.cfm?vn=221101">Nabro</a>, a volcano near the Eritrean-Ethiopian border, suddenly <a href="https://www.geog.cam.ac.uk/research/projects/nabro/">erupted</a> about seven years ago. There was no ground-based volcano monitoring at the time in Eritrea and the eruption was first observed from space by international scientists. The eruption <a href="http://www.irinnews.org/q-and/2011/07/06/thousands-need-aid-after-volcano-eruption">killed</a> seven people and left 12,000 people homeless. It also disrupted regional air traffic for several days. </p>
<p>To be better prepared for future eruptions there’s a need to understand and monitor poorly known volcanoes, even in remote places. </p>
<p>This is <a href="https://www.researchgate.net/project/RiftVolc-The-Past-Present-and-Future-of-Volcanism-in-the-Main-Ethiopian-Rift">what we do</a>. We are part of RiftVolc, a collaboration between scientists from the UK and Ethiopia, focused on understanding volcanism in the main Ethiopian rift, a stretch of 300km covering about 15% of East Africa’s volcanoes. We examine past eruptions, the sources and processes leading to <a href="https://theconversation.com/how-to-turn-a-volcano-into-a-power-station-with-a-little-help-from-satellites-86566">unrest in volcanoes</a> and the potential impact of future eruptions. </p>
<h2>Tracking hazards</h2>
<p>One way to assess future hazards from long-dormant volcanoes – those with limited or no historical eruptions – is to reconstruct their history using geological records, like rocks and sediment. The landscape around the volcanoes is covered in volcanic rocks that are the result of explosive eruptions that happened over the last 10,000 years. Volcanic ash deposits from these eruptions are also found within <a href="https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018GC007686">sediments</a> in nearby lakes. </p>
<p>This sediment tells us about what has happened in the past – for instance if volcanoes erupted on average every 10, 100 or 1000 years – but also about the style of activity; whether it was lava flows or big explosions. This gives us a good idea of what can happen in the future. Exploration of other volcanoes in the world show that, though every volcano is unique, the general patterns and style of activity tend to <a href="http://volcano.si.edu/faq/index.cfm?question=eruptionforecast">repeat themselves</a>. This means that with a better understanding of a volcano’s history we can inform policy makers and monitoring agencies responsible for disaster management. </p>
<p>The sequence of volcanic deposits shows that some volcanoes in central Ethiopia, like <a href="http://volcano.si.edu/volcano.cfm?vn=221290">Corbetti</a> and <a href="http://volcano.si.edu/volcano.cfm?vn=221270">Aluto</a>, are characterised by between one and four explosive eruptions per millennium. That is up to one every 250 years. </p>
<p>A new eruption from either of these volcanoes would cover several hundreds or even thousands of square kilometres, a size on the order of a thousand football fields, in a blanket of <a href="https://volcanoes.usgs.gov/vhp/tephra.html">volcanic ash</a> and severely disrupt the local infrastructure and economy, possibly also aviation. </p>
<p>Most volcanoes further north in the <a href="https://www.sciencedirect.com/science/article/pii/S0377027317303670?via%3Dihub">Main Ethiopian Rift</a> seem to have been less active in the last few thousand years, and have mostly had minor explosive eruptions and lava flows. Even such eruptions could however be destructive for local infrastructure. </p>
<p>The geology tells us how damaging a volcano could be and informs what strategies are needed for monitoring and mitigating risk. We can’t prevent eruptions, but by better understanding the ones that happened in the past, we can be better prepared for future ones.</p>
<h2>Volcanic benefits</h2>
<p>Another benefit of tracking volcanoes is that some findings can be useful for completely different reasons.</p>
<p>For example, all over the Main Ethiopian Rift we <a href="https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2011GC003662">find places</a> where hot volcanic gases and fluids are emitted. In some places, such <a href="https://theconversation.com/how-to-turn-a-volcano-into-a-power-station-with-a-little-help-from-satellites-86566">steam vents</a> can be used to create thriving resort economies through the creation of spas. </p>
<p>Volcanic fluids can also turn rocks to clay – serving as an excellent source material for <a href="https://en.wikipedia.org/wiki/Kaolinite">ceramics</a>.</p>
<p>And finally the high concentration of active volcanoes in the Rift area provides an advantage in generating <a href="http://www.thinkgeoenergy.com/new-study-estimates-10000-mw-geothermal-potential-in-ethiopia/">geothermal energy</a> – the use of water and steam, drilled from depth, to drive geothermal power generators creating electricity. Significant investment in geothermal energy development on multiple dormant volcanoes, with a total estimated potential of 10,000 MW, is <a href="https://www.bloomberg.com/news/articles/2018-02-05/ethiopian-geothermal-is-private-equity-s-next-4-billion-bet">expected</a> to turn Ethiopia into a regional renewable energy powerhouse. </p>
<p>In the short term, the socio-economic benefits associated with the volcanoes far outweigh the risks. But it remains critical to incorporate appropriate strategies towards risk reduction so that the natural resources offered by volcanoes can contribute to a sustainable future.</p><img src="https://counter.theconversation.com/content/106322/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Karen Fontijn received funding from the UK's Natural Environment Research Council. </span></em></p><p class="fine-print"><em><span>Gezahegn Yirgu does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>To be better prepared for future eruptions there’s a need to understand and monitor poorly known volcanoes, even in remote places.Karen Fontijn, Assistant Professor - Mineralogy/Volcanology, Université Libre de Bruxelles (ULB)Gezahegn Yirgu, Professor, Addis Ababa UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/708172017-01-05T14:32:51Z2017-01-05T14:32:51ZAfrica’s most toxic lakes are a paradise for fearless flamingos<figure><img src="https://images.theconversation.com/files/151839/original/image-20170105-18659-ut1vqh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">matthieu Gallet / shutterstock</span></span></figcaption></figure><p>The world’s most seemingly-toxic lakes are under threat. And they are also home to one of our most familiar birds: the flamingo.</p>
<p>All flamingo species have evolved to live in some of the planet’s most extreme wetlands, like caustic “soda lakes”, hypersaline lagoons or high-altitude salt flats. </p>
<p>One species, the <a href="http://www.arkive.org/lesser-flamingo/phoeniconaias-minor/">lesser flamingo</a>, has taken this relationship to the limit. Most are found in super-alkaline lakes throughout Africa’s Great Rift Valley, which host immense blooms of microscopic blue-green algae (called cyanobacteria). These <a href="http://ehjournal.biomedcentral.com/articles/10.1186/1476-069X-5-6">poisonous plants</a> produce chemicals that, in most animals, can fatally damage cells, the nervous system, and the liver. The lesser flamingo, however, can consume <a href="http://www.amusingplanet.com/2012/11/thousands-of-pink-flamingos-at-lake.html">enormous amounts</a> with no ill effects (unless you count their <a href="http://datazone.birdlife.org/species/factsheet/lesser-flamingo-phoeniconaias-minor/text">colourful plumage</a>, which comes from a pigment in the algae).</p>
<h2>Birds in paradise</h2>
<p>Two of the lesser flamingo’s preferred habitats, Lake Bogoria in Kenya and Lake Natron in Tanzania, are hypersaline and hostile to practically all other forms of life (Natron water can even <a href="https://theconversation.com/how-planet-earths-ice-skating-flamingos-collectively-get-in-the-mood-for-sex-68784">strip away human skin</a>). </p>
<p>For the flamingos this a bonus. Special tough skin and scales on their legs prevent burns, and they can drink water at near boiling point to collect freshwater from springs and geysers at lake edges. If no freshwater is available, flamingos can use glands in their head that remove salt, draining it out from their nasal cavity. </p>
<p>With few other animals able to cope in such conditions, there is minimal competition for food, and these toxic wetlands are home to massive flocks.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/151846/original/image-20170105-18641-rcy0zv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/151846/original/image-20170105-18641-rcy0zv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/151846/original/image-20170105-18641-rcy0zv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=394&fit=crop&dpr=1 600w, https://images.theconversation.com/files/151846/original/image-20170105-18641-rcy0zv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=394&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/151846/original/image-20170105-18641-rcy0zv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=394&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/151846/original/image-20170105-18641-rcy0zv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=495&fit=crop&dpr=1 754w, https://images.theconversation.com/files/151846/original/image-20170105-18641-rcy0zv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=495&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/151846/original/image-20170105-18641-rcy0zv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=495&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Feeding time on Lake Boringa.</span>
<span class="attribution"><span class="source">GUDKOV ANDREY / shutterstock</span></span>
</figcaption>
</figure>
<p>Million-strong gatherings provide several benefits. Mass <a href="https://theconversation.com/how-planet-earths-ice-skating-flamingos-collectively-get-in-the-mood-for-sex-68784">synchronised nesting</a> gives flamingos the best possible chance to raise the maximum number of chicks, while on choppy days a dense mass of birds swimming together also helps create the <a href="http://datazone.birdlife.org/species/factsheet/lesser-flamingo-phoeniconaias-minor/text">optimal feeding environment</a> (still water) within the centre of the group. Sheer numbers also make it harder for predators like hyenas or jackals to identify individual victims.</p>
<p>As such, a single flamingo is not a happy flamingo. The species is happiest in huge gatherings, and these won’t occur around any old lake – the lesser flamingo specifically needs its toxic, salty paradise. </p>
<p>But these places are rare. Across the six flamingo species there are only 30 or so regularly used breeding sites worldwide and, while the global population of <a href="http://www.iucnredlist.org/details/22697369/0">around 3.2m lesser flamingos</a> is impressive, it is largely reliant on a few huge groups (<a href="https://www.hindawi.com/journals/ijbd/2014/295362/">about 75%</a> nest at Lake Natron alone). What if something happens to one of their highly-specialised breeding sites?</p>
<p>Unlike many other species that can still breed in smaller populations as their habitats become damaged, these birds cannot easily survive in small groups. Having evolved in such a hostile environment with few rivals, they would have trouble adapting to a more competitive lifestyle elsewhere. With most of their eggs in one toxic basket, the lesser flamingo is unusually vulnerable for a species with millions of individuals.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/151850/original/image-20170105-18665-xlh6a9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/151850/original/image-20170105-18665-xlh6a9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/151850/original/image-20170105-18665-xlh6a9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/151850/original/image-20170105-18665-xlh6a9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/151850/original/image-20170105-18665-xlh6a9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/151850/original/image-20170105-18665-xlh6a9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/151850/original/image-20170105-18665-xlh6a9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/151850/original/image-20170105-18665-xlh6a9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Lesser flamingos’ Latin name <em>Phoeniconaias minor</em> means ‘little crimson water nymph’, an apt description of their dancing, ballet-style moves.</span>
<span class="attribution"><span class="source">Steffen Foerster / shutterstock</span></span>
</figcaption>
</figure>
<p>Indeed, the number of lesser flamingos in the wild is already decreasing each year. And humans are to blame. Wetland habitats have been polluted by agricultural chemicals and sewage, feeding and breeding grounds have been disturbed, and declining algal blooms mean some populations are <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1529-8817.2010.00915.x/full">starving to death</a>.</p>
<p>Even a diet of toxic algae can’t save flamingos from ecological disturbances. If humans take too much water from a lake, or climate change causes excess evaporation, then salinity levels will become unstable. Populations of cyanobacteria can explode and the birds end up <a href="http://www.sciencedirect.com/science/article/pii/S1568988305001101">consuming new species</a> which can poison them and cause <a href="http://www.saltworkconsultants.com/blog/lake-nakuru-life-response-to-feast-and-famine-in-schizohaline-lacustrine-hydrologies">mass deaths</a>.</p>
<h2>Soda ash mining threatens the entire species</h2>
<p>Attempts to extract sodium carbonate (a useful industrial material known as soda ash) from Lake Natron represents another danger. Mining would disturb the birds, who like privacy when breeding and tend to nest far from shore, on remote islands that have been isolated by flooding. It would also make the water more choppy, affecting their food gathering. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/151657/original/image-20170103-29222-1rjc83f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/151657/original/image-20170103-29222-1rjc83f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/151657/original/image-20170103-29222-1rjc83f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/151657/original/image-20170103-29222-1rjc83f.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/151657/original/image-20170103-29222-1rjc83f.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/151657/original/image-20170103-29222-1rjc83f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/151657/original/image-20170103-29222-1rjc83f.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/151657/original/image-20170103-29222-1rjc83f.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The same algae that gives flamingos their colour sometimes turns Lake Natron red.</span>
<span class="attribution"><span class="source">Bildagentur Zoonar GmbH / shutterstock</span></span>
</figcaption>
</figure>
<p>Given how slow flamingos are at adapting and changing to new nesting areas, any Natron development must be avoided. Anthropogenic disturbances have previously caused lesser flamingos to <a href="http://jncc.defra.gov.uk/PDF/pub07_waterbirds_part3.4.5.pdf">abandon suitable breeding sites</a>, and back in 1993, polluted water in Lake Bogoria and nearby Nakuru killed more than <a href="http://www.worldlakes.org/uploads/18_Lake_Nakuru_27February2006.pdf">20,000 lesser flamingos</a> – the first of a series of recurring deaths.</p>
<p>The latest mining proposal has been withdrawn but such developments <a href="http://africageographic.com/blog/tanzania-mine-worlds-important-flamingo-breeding-ground/">haven’t been completely shelved</a>. Conservation groups <a href="http://www.rspb.org.uk/our-work/our-positions-and-campaigns/campaigning-for-nature/casework/details.aspx?id=tcm:9-228219">remain alert</a>. Monitoring and protecting the population at Lake Natron is the top priority for lesser flamingo conservation, according to a <a href="http://www.iucnredlist.org/details/22697369/0">recent assessment</a> by BirdLife International. Large-scale soda ash extraction, the report says, would be “disastrous for the species” and could see the flamingos become officially “vulnerable” or even “endangered”.</p>
<p>The importance of these unique, and apparently hostile, wetlands is clear to see. Life in the Rift Valley lakes is a delicate balance. And it is clear that we are already harming these unique and fragile ecosystems. If humans were to cause drastic changes, their spectacular pink inhabitants would vanish forever.</p><img src="https://counter.theconversation.com/content/70817/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Paul Rose is a WWT / University of Exeter PhD student. He is affiliated with the IUCN Flamingo Specialist Group. WWT coordinates the Conservation Action Plan for the lesser flamingo. </span></em></p>Millions of birds breed in lakes so alkaline they can burn human skin.Paul Rose, Associate Fellow, Centre for Research in Animal Behaviour, University of ExeterLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/198622013-11-07T06:11:35Z2013-11-07T06:11:35ZHow a changing landscape and climate shaped early humans<figure><img src="https://images.theconversation.com/files/34563/original/2yy5c4w2-1383764652.jpg?ixlib=rb-1.1.0&rect=0%2C269%2C2091%2C1868&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Lucy, born 3.2m years ago.</span> <span class="attribution"><span class="source">Pat Sullivan/AP</span></span></figcaption></figure><p>It should not be a surprise that East Africa was a hotbed of evolution, because over the last five million years everything about the landscape has changed.</p>
<p>The extraordinary forces of <a href="http://www.bbc.co.uk/science/earth/surface_and_interior/plate_tectonics">plate tectonics</a> and a changing climate have transformed East Africa from a relatively flat, forested region to a mountainous fragmented landscape dominated by the rapid appearance and disappearance of huge, deep-water lakes. And from this highly variable landscape emerged an ape smart enough to question its own existence.</p>
<h2>A cradle rocked by tectonics</h2>
<p>Twenty million years ago the Indian and Asian continental plates clashed and pushed up the massive <a href="http://ngm.nationalgeographic.com/2010/04/tibetan-plateau/larmer-text">Tibetan plateau</a>. In summer this plateau acts as a huge heat engine, absorbing solar energy which it transfers to the atmosphere, causing immense convection currents. With all this hot air rising, air is sucked in from all round, including moist air from the Indian Ocean that produces intense South East Asian monsoons.</p>
<p>This has a knock on affect of drawing moisture away from the African continent, and it was this that began the progressive drying out of East Africa. In terms of human evolution, this distinct split between the climate of Asia and Africa coincides with the split between Asian and African apes, the latter eventually evolving into us.</p>
<p>At the same time as the peaks of Tibet were thrusting upwards, the <a href="http://www.wwnorton.com/college/geo/egeo2/content/animations/2_7.htm">rifting process</a> began in Ethiopia and gradually moved south finishing in Mozambique about one million years ago. This rifting was caused by a hotspot of magma under northern East Africa heating the crust causing it to split down the middle like an overdone apple pie. </p>
<p>The rifting process produced a deep, wide, hanging valley half a mile above sea level with uplifted shoulders or mountain ranges on either side rising up to two miles high. The affects of the <a href="http://geology.com/articles/east-africa-rift.shtml">Rift Valley</a> formation on the local climate was dramatic.</p>
<p>The East Rift’s mountains prevented moist air from the Indian Ocean from passing over East Africa, causing the region to dry even further. The topography of East Africa completely changed: from a homogeneous flat region covered in moist forest, to a mountainous landscape with plateaus and deep rift valleys, where vegetation varied from cloud forest to desert scrub.</p>
<h2>Evolution, our coping strategy</h2>
<p>Presented with fragmented vegetation and greater distances between sources of food may have led to the evolution of human bipedalism – <a href="http://blogs.smithsonianmag.com/hominids/2012/08/becoming-human-the-evolution-of-walking-upright/">walking upright on two legs</a> – around six million years ago. These highly successful early bipedal hominins such as <a href="http://archaeologyinfo.com/ardipithecus-ramidus/">Ardipithecus ramidus</a> or <a href="http://www.bbc.co.uk/sn/prehistoric_life/human/human_evolution/mother_of_man1.shtml">Australopithecus afarensis</a>, were nevertheless relatively small-brained, with a cranial capacity of about 450cm<sup>3</sup> compared with modern humans with over 1,500cm<sup>3.</sup></p>
<p>The development of the East African Rift valley fragmented the landscape and formed a large number of separate lake basins. The mountainous landscape makes these basins very sensitive to small changes in rainfall. <a href="http://www.geo.uni-potsdam.de/member-details/show/108.html">Martin Trauth</a> of Potsdam University and colleagues found geological evidence that deep, freshwater lakes existed around 2.6 million, 1.8 million and 1 million years ago – key dates in human evolutionary history.</p>
<p>During each of these periods the local climate of East Africa varied over a 20,000-year cycle, from extreme aridity to very wet conditions. So our ancestors may have had an idyllic environment, cruelly taken away as the lake dried up over a few generations. Thousands of years later the lake would return and the cycle would begin again. The 20,000-year cycle is driven by changes in the Earth’s orbit around the sun, which affects the amount of sunlight received during any particular season. In East Africa it had a significant influence on the timing and duration of the two wet seasons.</p>
<p>The <a href="http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0076750">recent study</a> published in the journal PloS ONE by <a href="http://www.ls.manchester.ac.uk/people/profile/?personid=25440">Susanne Shultz</a> of Manchester University and me statistically links for the first time the emergence of new hominin species, expanding brain capacity, and the movement out of Africa to the appearance and disappearance of deep freshwater lakes (confirming the original work by Martin Trauth and myself).</p>
<p>The most profound period for human evolution occurs at about 1.8 million years ago, a period which records the highest diversity of hominin species, including the appearance of <a href="http://humanorigins.si.edu/evidence/human-fossils/species/homo-rudolfensis">Homo rudolfensis</a> and <a href="http://humanorigins.si.edu/evidence/human-fossils/species/homo-erectus">Homo erectus</a> with a substantially larger brain capacity of 900cm<sup>3,</sup> and the first major dispersal of our ancient human ancesters out of East Africa into Eurasia. During this period, the ephemeral deep-freshwater lakes appeared and disappeared along the whole length of the East Africa Rift valley, causing fundamental environmental changes that pushed these new species out of Africa.</p>
<p>We have now started to put together a coherent picture of how the changing East African landscape has driven human evolution over the last ten million years. The region has altered beyond all recognition, from flat and forested to one filled with spectacular, two-mile-high mountains, savannahs and tropical forests. By priming the land to form lake basins that were sensitive to small changes in rainfall, extreme climate pulses of alternately arid and wet period occurred and had a profound effect on all the animals living in East Africa. The powerful forces of plate tectonics and climate variability ultimately led to our hominid ancestors’ development and their dispersal from Africa, to the Caucasus, the <a href="http://www.ancient.eu.com/Fertile_Crescent/">Fertile Crescent</a>, and ultimately the rest of the world.</p><img src="https://counter.theconversation.com/content/19862/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mark Maslin receives funding from the Royal Society and NERC.</span></em></p>It should not be a surprise that East Africa was a hotbed of evolution, because over the last five million years everything about the landscape has changed. The extraordinary forces of plate tectonics…Mark Maslin, Professor of Climatology, UCLLicensed as Creative Commons – attribution, no derivatives.