Transcript File - Vagabond Geology

Life Long Learning: Fall 2012
Vagabonds Tramp Eastern Africa
Session Five
Let’s
recalllet’s
that focus
I’m postulating
that the great
Now
on Tanzania
nations of human history were and are
located, because of continental drift, in the
Last week Sandi took us to Tanzania and the East African Rift
“Vagabonds
Tramp through
Eastern
wherehad
the
Northern
Temperate
Zone,
andAfrica:
thatappeared.
they
lakes where
fossils indicated
humans
first
unique geology of the East African Rifts produced the
You
and I looked
at rock types,
welding ofplus
geosynclines
geologic
resources
of the
farmland,
iron,
advent of the human species and the Nile flood plain
as mountains
that
renewed
the20
continental
crustoil
periodically,
th century,
coal
and
the
shaped
thein
beginning
of human history”
and the farm land of Zimbabwe
Central Africa: Natural Resources
Focus on Tanzania
Tanzania: one of four former German colonies in Africa
German Colonies in Africa
African Geologic Map
German Colonies in Africa
Natural Resources: largely in Igneous & Metamorphic Rocks
Africa today
Natural Resources
Now the natural resources of Tanzania
Copper
Tin
Iron
Focus on former
German African
Colonies
Note: No Iron or Coal
The Natural Resources of Tanzania
Now, remember what Sandi said
caused the long, narrow lakes?
But before we go to the lakes, let’s remember
the farmland in Zimbabwe’s
very old, Pre-Cambrian.
Gold
Why did weathering there produce farmland and not here?
Almost no farming,
no iron, & no coal
Why little or no farmland?
These very old, Pre-Cambrian rocks weathered into
thin soils suitable for grazing, not rich farm soils
Conclusions: Rock type determines the soils
produced by weathering, not rock age.
Focus on possible farming areas in Zimbabwe
Focus on this province
Focus on possible farming areas in Zimbabwe
Back to the regional view and another possible area
of farming
Note: no farming in river flood plain but
all the surrounding hills are cultivated
The regional view and another possible area
of farming
Focus on this province
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 soils
Rock that weathers
into thin soils
Now to the southern area
Was Zimbabwe a great African nation
before Rock
it was
Southern
Rhodesia?
weathering into
thick, rick farmland
Rock weathering
into thin soil
Conclusion:
Rock composition makes all the difference!
Pre-colonial nations of Africa
Now to the long narrow Rift Valley Lakes
in Tanzania
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
Plate Tectonics: Uplift and rift faulting
over a sub-crustal (mantel) convection cell
Tanzania
East Africa:
Triple junction
Rift Valleys formed
& Volcanoes
Why was this event important?
More
detail
on the event
East African
This
unique
geological
coincides with
thejunction
advent of
triple
the human race here!
East African Triple Junction
East Africa Rift
Valley
Western
Rift Valley
Eastern
East Africa:
junction
RiftTriple
Valley
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?
Current oil and gas exploration in
the East African Rifts
Kenya oil
discovery
Tanzania
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.
Rift Valley Exploration History
In the early 1980’s Duke University designed
a “portable” seismic survey vessel, conducted
extensive seismic
subsurface
imaging
Back
to Africa
and of the
African rifts, which was financed by several major oil
Early
Human
History
&
Geology
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
the prospects
Note:
Currently
oil &ofgas
exploration is being
caused
all major
decline
investing
the
done
in thecompanies
rift valleystoof
Kenya
because
additional funds needed to define drill sites.
they contain the world’s richest
source rocks (25 % organic C)
http://bulletin.geoscienceworld.org/content/98/4/439.abstract
Africa: Early Human History & Geology
Note: The upper Nile River is in
the Northern Temperate Zone
Rift extensions & crustal
warping produces
rivers that provide
provides routes for
humans out of the
Tropics of Africa
The Tropics
Nile River flood plain:
Bronze Age empire built
on large scale agriculture
in the Nile River flood plain
East African
Rift Valleys &
the Advent
of Humans
Proposition:
The geology of Africa shaped the advent & early history of Humans
Now let’s look more closely at the
geology Tanzania
Tropics
Zimbabwe
Tropics
Zimbabwe
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; Topographic Map
Note:
Ruvuma River delta
Long, narrow lakes
Up-land topography like
Zimbabwe
Tanzania
Questions:
Is the Ruvuma building a
geosyncline prospective
for oil & gas?
Are the lakes part of the East
African rift system?
Will the up-land have farming
like Zimbabwe?
Ruvuma River
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 jungle
Maybe small geosyncline
prospective for oil & gas
Let’s look at current oil exploration
in the Ruvuma geosyncline, here
Current Oil & Gas Exploration in the
Ruvuma river geosyncline
Numerous small prospects
Prospects in cross section
Numerous small, complex prospects
Prospects in cross section
Now more detail
Detached Folds
Look at the blue layer
it is a “detached” fold
What is a detached fold?
Detached Folds
Detached folds, a massive slump
A modern example affecting the surface
Detached Folds
Windjammer Palma FB Thrust Play
Lagosta Oligocene & Eocene Deepwater Fans
Conclusions:
Small geosynclines can be prospective
Back to the topographic map of Tanzania.
for oil & gas but here they are very complex.
Any
might have
farm land?
Theyother
might rivers
also bethat
prototypes
for understanding
the oldest part of large geosynclines
Tanzania; Topographic Map
Tanzania
Here?
Ruvuma River
Here?
No farming,
only jungle
Here?
Looks like grazing land.
What does the natural resources map show?
East Central Africa:
Natural Resources
Focus on Tanzania
Focus on Natural Resources in Tanzania
Gold
Can we find the cotton south of Lake Victoria?
No farming (little cotton)
no iron, & no coal
Cotton fields?
Next week:
Advents of humans, Kenya, & Egypt