life long learning: fall 2012 vagabonds tramp eastern africa session five “vagabonds tramp through...
TRANSCRIPT
Life Long Learning: Fall 2012
Vagabonds Tramp Eastern AfricaSession Five
“Vagabonds Tramp through Eastern Africa: where the unique geology of the East African Rifts produced the advent of the human species and the Nile flood plain
shaped the beginning of human history”
Let’s recall that I’m postulating that the great nations of human history were and are
located, because of continental drift, in the Northern Temperate Zone, and that they had
geologic resources of farmland, plus iron, coal and in the 20th century, oil
Last week Sandi took us to Tanzania and the East African Rift lakes where fossils indicated humans first appeared.
You and I looked at rock types, the welding of geosynclinesas mountains that renewed the continental crust periodically,
and the farm land of Zimbabwe
Now let’s focus on Tanzania
Central Africa: Natural ResourcesFocus on Tanzania
Tanzania: one of four former German colonies in Africa
Natural Resources: largely in Igneous & Metamorphic Rocks
CopperTinIron
Africa todayNatural Resources
Focus on formerGerman AfricanColonies Note: No Iron or Coal
Now the natural resources of Tanzania
Almost no farming, no iron, & no coal
Gold
These very old, Pre-Cambrian rocks weathered into thin soils suitable for grazing, not rich farm soils
Now, remember what Sandi said caused the long, narrow lakes?
Why little or no farmland?
Conclusions: Rock type determines the soilsproduced by weathering, not rock age.
But before we go to the lakes, let’s remember the farmland in Zimbabwe’s very old, Pre-Cambrian.
Why did weathering there produce farmland and not here?
The Natural Resources of Tanzania
Focus on possible farming areas in Zimbabwe
Note: no farming in river flood plain but all the surrounding hills are cultivated
Back to the regional view and another possible area of farming
Again the river flood plain is not cultivated but the surrounding hills are completely farmed
Conclusion: Zimbabwe, Southern Rhodesia, though in the Tropics has great potential for becoming a prosperous nation
based on its natural resources
Does the farmland stop when we leave the light gray areas on the NASA maps?
Eastern limit of the northern farmland
Rock that weathers into thick, rich soilsRock that weathers into thin soils
Now to the southern area
Rock weathering into thick, rick farmland
Rock weathering into thin soil
Conclusion: Rock composition makes all the difference!
Was Zimbabwe a great African nation before it was Southern Rhodesia?
Long Narrow Rift Valley Lakes
They are the southern extension of the East African Rift System
Let’s look at the “big picture”
Complex Shape of Mantle Convection Cells
Can you find Africa in the top panel?
East African Triple Junction
Rift Valleys formed & Volcanoes
Plate Tectonics: Uplift and rift faulting over a sub-crustal (mantel) convection cell
Why was this event important?This unique geological event coincides with the advent of
the human race here!
East Africa:Triple junction
More detail on the East African triple junction
Tanzania
East Africa Rift East Africa Rift ValleyValley
Eastern Eastern Rift ValleyRift ValleyWestern Western
Rift ValleyRift Valley
East Africa:Triple junction
East African Triple Junction
The triple junction up close
The triple junction up close:rift valleys and volcanoes
Another view focused on the East African Rifts
Kenya oil discovery
Tanzania
Current oil and gas exploration in the East African Rifts
Comments: The economic viability of this discovery will depend on what deeper drilling encounters. Its remote location will require a very expensive pipe line. Commercial production, if any, is years in the future.
http://bulletin.geoscienceworld.org/content/98/4/439.abstract
Rift Valley Exploration History
In the early 1980’s Duke University designed a “portable” seismic survey vessel, conducted extensive seismic subsurface imaging of the African rifts, which was financed by several major oil companies. Results indicated possible oil & gas accumulations but the remote location of the rifts, the excessive water depths of the rift lakes, and the complex nature of the prospects caused all major companies to decline investing the additional funds needed to define drill sites.
Note: Currently oil & gas exploration is being done in the rift valleys of Kenya because
they contain the world’s richest source rocks (25 % organic C)
Back to Africa and Early Human History & Geology
Africa: Early Human History & Geology
East AfricanRift Valleys & the Advent of Humans
Rift extensions & crustal warping produces rivers that provideprovides routes for humans out of theTropics of Africa
Nile River flood plain:Bronze Age empire builton large scale agriculture in the Nile River flood plain
Now let’s look more closely at the geology Tanzania
The Tropics
Note: The upper Nile River is inthe Northern Temperate Zone
Proposition: The geology of Africa shaped the advent & early history of Humans
Age of the rocks are at the surface in Tanzania
Mostly purple, Pre-Cambrian metamorphic and Igneous rocks >500 million years old, very similar to Zimbabwe (in age)
And how have these rocks been affected by erosion; the topographic map
Tanzania
Ruvuma River
Tanzania; Topographic Map
Note:Ruvuma River deltaLong, narrow lakesUp-land topography like
Zimbabwe
Questions:Is the Ruvuma building a
geosyncline prospectivefor oil & gas?
Are the lakes part of the East African rift system?Will the up-land have farming
like Zimbabwe?
The Ruvuma delta up close: flood plains & farm land?
No farm land, only jungleMaybe small geosyncline prospective for oil & gas
Let’s look at current oil exploration in the Ruvuma geosyncline, here
Tanzania
Mozambique
Tanzania
Mozambique
Current Oil & Gas Exploration in theRuvuma river geosyncline
Numerous small prospects
Lagosta Oligocene & Eocene Deepwater Fans
Back to the topographic map of Tanzania. Any other rivers that might have farm land?
Conclusions:Small geosynclines can be prospective
for oil & gas but here they are very complex.They might also be prototypes for understanding
the oldest part of large geosynclines
No farming (little cotton) no iron, & no coal
Gold
Can we find the cotton south of Lake Victoria?
Focus on Natural Resources in Tanzania