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

German Colonies in Africa

African Geologic MapGerman 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

Focus on this province

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

Focus on this province

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?

Now to the long narrow Rift Valley Lakes in Tanzania

Pre-colonial nations of Africa

Long Narrow Rift Valley Lakes

They are the southern extension of the East African Rift System

Let’s look at the “big picture”

Earthquake Epicenters: 25 years Focus on Africa

East African Triple Junction

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

Another view focused on the East African Rifts

Might there be oil and gas in the 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

Zimbabwe

Tropics

Zimbabwe

Tropics

What age rocks are at the surface in Tanzania?

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?

Google Earth view of Tanzania & Vicinity

The Ruvuma delta up close: flood plains & farm land?

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

Numerous small, complex prospects

Prospects in cross section

Prospects in cross section

Now more detail

Detached FoldsLook at the blue layer it is a “detached” fold

What is a detached fold?

Detached Folds

Detached folds, a massive slumpA modern example affecting the surface

Detached Folds

Windjammer Palma FB Thrust Play

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

Tanzania

Ruvuma River

Tanzania; Topographic Map

Here?

No farming, only jungle

Here?

Here?

Looks like grazing land.What does the natural resources map show?

East Central Africa: Natural Resources

Focus on Tanzania

No farming (little cotton) no iron, & no coal

Gold

Can we find the cotton south of Lake Victoria?

Focus on Natural Resources in Tanzania

Cotton fields?

Next week: Advents of humans, Kenya, & Egypt