Monday, August 14, 2017

The East African Rift Valley: Where We Became People

Annamaria on Monday



To geologists, the most interesting place is in East Africa: the largest seismically active rift system on earth.  What’s happening there is that new tectonic plates are being formed by their spreading apart from the landmass.  This the opposite of where tectonic plates have pushed into each other to form mountain ranges.  In this case, when hunks of a tectonic plate separate, it causes chasms.  In the distant past, other such divorces have taken place on our sacred planet, but they are all now underwater or silted in—no longer active.


The separations—and there are two of them—taking place in East Africa have been going on since the onset of the Miocene about 25 million years ago.   The Nubian Plate and the Somali Plate are still moving, now at the rate of six or seven millimeters per year.  In another 10 million years or so, the Somali Plate will be completely broken off, and the sea will surround it.


Earth scientists are fascinated to be able to study this process and to theorize about why and how it is happening in this geologic wonder of the world.   The rift area includes not only parts of Ethiopia and Somalia, but also extends into Kenya, Uganda, Tanzania, and the African Great Lakes.  The rift is deepest north of Nairobi.  Theories vary as to why this process is underway just there and no where else on earth.  It seems that, like many thorny scientific questions, this one is a result of interactions of more than one force, making it difficult to sort out.


We know that the East African Rift Zone is the site of many dormant and active volcanoes, fifty of them in Ethiopia alone.  The Crater Highlands of Tanzania are part of this system, even though they now lie outside the rift area.  One of the active volcanoes is unique: The magma of the Ol Doinyo Lengai volcano contains no silica, so it has extremely low viscosity.  National Geographic described it this way: “Its lava fountains crystallize in midair then shatter like glass.”  Wow, wouldn’t I love to witness that!

Ol Doinyo Lengai
Most fascinating to me is that this is where our race Homo Sapiens evolved.  The bones of our hominid ancestors have emerged from the sediments of the Rift Valley highlands.  These include the famous “Lucy”, the partial australopithecine skeleton from 3 million years ago, discovered by anthropologist Donald Johanson.   The rift in Ethiopia more recently yielded two other 10-million-year-old hominid ancestors: Chororapithecus abyssinicus and Nakalipithecus nakayamai.


Since so many hominid fossils have been found in the Great Rift Valley, scientists have begun to think that the evolving conditions there played a pivotal role in the development of our species.  Current theorists believe that the local situation caused the climate to alternate between wet and arid, which forced our hominid ancestors to adapt by becoming bipedal, increasing their brain power, and developing culturally.  My favorite article on this theory is the 2008 paper by Beth Christensen and Mark Maslin, delightfully titled “Rocking the Cradle of Humanity.”



For me personally, the African wilderness plays in my blood and in my soul in such a way that my response runs far deeper than ordinary joy.   This is where our species evolved, and I believe that, when we human beings go there, regardless of where we were born, on a cellular level, we recognize the place as home.  Ever since I first went, when I am not there, in my soul, I am homesick for it.



15 comments:

  1. I've often thought, wouldn't it be wonderful to live slowly, for millions of years, and watch the mountains rise, the plains tear apart, the ocean pour in.

    Alas, we're but mayflies in a hurricane...

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    1. EvKa, wouldn't it be great if we could see it in time lapse? Maybe someone will make (has made?) a computer simulation of it. I have to say that I admire the geologists their patience. They must know better than any of us, what mayflies we really are. Yet they go deep (!) into the subject, looking for minute clues to help us see our Earth for what it really is.

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  2. It sure is humbling to be where our human ancestors began, where Lucy's remains were found. It must bring great joy to experience being there.

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    1. Yes, Kathy. And I wish those disgusting white supremacists would understand that we are all Africans in our blood. But then their God created the earth in seven days, right?

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  3. Im so glad you had this once in a lifetime opportunity and that you shared it with us.

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    1. Thank you, Sufata. I feel so fortunate that my childhood fantasies about traveling to exotic places come true.

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  4. Wonderful blog, Annamaria. Yes, somebody needs to do a CGI time-lapse of the earth forming. They probably already have ...

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    1. Your request, my pavlovian response...

      https://www.youtube.com/watch?v=WaUk94AdXPA

      It's fun to watch it over and over several times, as you miss various parts of the world forming. For example, India splitting off from between what becomes S. Africa and Antarctica and sailing NE and crashing into Asia.

      Then, for another view (a little more difficult to understand) which also predicts what the earth will look like 100 million years in the future:

      https://www.youtube.com/watch?v=uGcDed4xVD4

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    2. Then there's this one that's maybe the best of the lot. Fun watching N. and S. America play ping-pong between Europe and Asia...
      https://www.youtube.com/watch?v=uLahVJNnoZ4

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    3. Thank you, EvKa! Those Images are fascinating. I like the last one best too. I watched it a couple of times. It is beautiful as well as fascinating in the information is communicate.

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    4. if anyone was going to find those films for us, I knew it would be you, EvKa! Thank YOU!!

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  5. Yes, those idiotic rabid white supremacists should learn some basics, which is probably impossible, given their pro-Nazi, pro-KKK actions and words.

    Yes, and I'm furious that they harassed a synagogue in Charlottesville with fire-arm toting big buys outside the building staring at it and its congregants.

    Well, we'll see is this whole outrage is Trump's final undoing. That he gave the false equivalency of equating Nazis and Klan with anti-racists and said "there were good people" in the white supremacist march may be the final straw that broke the camel's back.

    The business council members all quit. Just read a Tennessee Congressperson Steve Cohen is presenting Articles of Impeachment based on Trump's remarks post-Charlottesville.

    From hearing young people who were there tell it, the situation was harrowing and dangerous. They were facing people with helmets, shields, tear gas, mace, clubs, and some had huge guns -- which were pointed at the "counter-protesters."

    I'm so sorry about hero Heather Heyer and the serious injures of many people, but am glad worse didn't happen, given the intense hatred of the far-right, who have weapons.

    Counter-protesters had signs and banners and their voices. They also had unity.

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  6. I meant "big guys" with guns outside the synagogue.

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  7. It's the one area in Africa that I would really like to see before I can't.

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  8. I love the spirit, your love of the place, and time lapse links. For musical accompaniment, here's a different sort of "Rocking the Cradle," https://www.youtube.com/watch?v=k7SYpFL5dFk

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