life long learning: fall 2012 vagabonds tramp eastern africa session three “vagabonds tramp...

Life Long Learning: Fall 2012

Vagabonds Tramp Eastern AfricaSession Three

“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 from last week that the great nations of human history were located in the Northern Temperate Zone, that they had extensive farmland, plus iron and coal

Then let’s apply what we’re learned to the country of Zimbabwe

First, remember the amazing geological discoveries of the last half of the 20th century

Five Amazing Geological Discoveries of the Second Half of the 20th Century

2. Continental Drift3. Absolute Age Dating4. Paleo-magnetics5. Plate Tectonics

Last week we mentioned the discovery of Oceanic Crust which is one of five amazing geological discoveries in the last half of the

20th century

1. Oceanic Crust

Continental Crust

Co

ntin

ental C

rust

Continental Crust

Oceanic Crust

Mid Ocean “ridge”

African Plate: African Continental crust

plus surrounding oceanic crust

Last week we also showed the location of the world’s great nations

Tropics

Northern Temperate Zone

Southern Temperate Zone

What we’ll try to get you to believe in the next 5 weeks

First Empires (farming major river flood plains)

Green hills lands with Fe and Coal (invade farming lands)

Conclusions on what is required for a land to become a world power1. Continental drift and plate tectonic put Eurasia in the ideal

location for early farming empires2. Plate tectonics (mountain building) exposed Fe and Coal in

hill lands initiating conflict with farming empires (except in China)3. No world powers or sustainable religions have or will be

developed in the tropics or the southern in the southern temperate zone

Where did the world-wide religions originate?

Tropics






Where did the world-wide religions originate?

Judaism

HinduismConfucianismBuddhism

ChristianityMohammedism

Conclusions: Geological events that shape human history are;Continental driftPlate tectonicsAbsolute age datingPaleo-magneticsNatural resources of farm land, iron, coal, and oil

Then let’s see if this can be applied to the country of Zimbabwe

But first let’s see where the greatest concentrations of iron and coal are located

Tropics






Where are the greatest concentrations of Iron & Coal?

Judaism

HinduismConfucianismBuddhism

ChristianityMohammedism

Conclusions: Geological events that shape human history are;Continental driftPlate tectonicsAbsolute age datingPaleo-magneticsNatural resources of farm land, iron, coal, and oil

Now let’s see if this can be applied to the country of Zimbabwe

Course definition of eastern Africa

Focus on Zimbabwe

Tropics

What rocks are at the surface in Zimbabwe?

Geologic Map of Africa Shows the age of rocks at the surface

Zimbabwe

500 million year old rocks at the surface

Tropics

Geologic Map of Southern Africa Focus on Zimbabwe

Zimbabwe

500 million year old rocks at the surface

Remember that rivers historically are important for farming. Are there rivers in Zimbabwe that support large scale farming?

Tropics

Zimbabwe

Tropics

Zambezi River

Limpopo River

Tropics

Zimbabwe

River drainage divide

Conclusion: No major river flood plains

But let’s look at the topographic map

Limpopo River

Zambezi River

Zimbabwe

Tropics

What are the rocks like at the surface in Zimbabwe?

Very complex geology

What are the archeological historic ages &the geological ages of geology?

Geological Map of ZimbabweGeologic Maps show age and rock type at the surface if all soil

& vegetation were removed

Note that the Limpopo drainage has the most very old rocks

Major river drainage divide line

Geologic Ages of Historic TimeGeologic Ages of Historic Time

Iron, Coal, Petroleum, & Uranium Age 1950 to PresentIron, Coal, Petroleum, & Uranium Age 1950 to PresentIron, Coal, & Oil AgeIron, Coal, & Oil Age 1900 to 1950 AD 1900 to 1950 AD

Iron & Coal: Industrial Age 1700 to 1830 ADIron & Coal: Industrial Age 1700 to 1830 ADIron & Coal: RenaissanceIron & Coal: Renaissance

1450 to 1700 AD1450 to 1700 ADIron & Coal: Middle AgesIron & Coal: Middle Ages

470 to 1450 AD 470 to 1450 ADIron Age 2 Rome to 470 ADIron Age 2 Rome to 470 AD

750 BCE750 BCEIron Age 1 GreeceIron Age 1 Greece 1400 to 750 BCE 1400 to 750 BCEBronze AgeBronze Age 3300 to 1400 BCE 3300 to 1400 BCE

Copper AgeCopper Age 3300 to 3000 BCE 3300 to 3000 BCEStone Age (end of Ice Age) 70,000 to 3300 BCEStone Age (end of Ice Age) 70,000 to 3300 BCE

Copper, tin, arsenic, & zinc

Flint & Obsidian

Iron Age

Iron-Coal Age

Iron, Coal, Oil AgeNow the geologic ages of the 4.8 billion year

old Earth

Large scale Farming

Geologic Time: 4.8 Billion Years

Pre-Cambrian

570 million to 4.9 billion years

ago

Age of most rocks at the surface in ZimbabweVery old, may have metal ores

What are the natural resources of Zimbabwe, is there farm-land, iron, and coal in Zimbabwe?

The natural resources of southern Africa

Focus on Zimbabwe

Coal

Iron

The natural resources of Zimbabwe

Farmland

Grazing land

Tropics

Conclusions: Even thought Zimbabwe is in the Tropics, it is high enough to be largely

above jungle and it has significant farm land plus iron and coal that could support the

development of a important nation.

What does Google-earth show us about the farm and grazing land of Zimbabwe?

Google-Earth: Southern Africa

Zimbabwe

Limpopo River

Zambezi River

Carving Landscapes (topography)Destruction of the Continental Crust

Focus on possible farming areas in Zimbabwe


Focus on this province


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

What geological processes created this topography of Zimbabwe?

Carving Landscapes (topography)Destruction of the Continental Crust

Geologic ProcessesWeathering & Erosion

Destruction of rocks which creates soil, rock debris, & topography 28

WEATHERING;What are the products of weathering

Rock Debris:Size classification;

Boulders, cobbles, gravel, pebbles, sands, and mud

Rock “Solutions”Composition; Debris:

Quartz Sand (silica) Muds (clays: hydrous Al Silicates) Solutions (mostly Ca, C, O) 29

WEATHERING: How is it done?

Water!!!

Sun Light

Heating and Cooling

Natural Acids

TIME TIME TIME30


Water!!!

Abrasion by: Falling RainFlowing Streams and Rivers

31


Water!!!

Sun Light (radiation)

32


Water!!!

Sun Light

Heating and Cooling daily expansion and contraction

33


Water

Sun Light

Heating and Cooling

Natural AcidsAcid Rain (natural)

Humic Acid (plant decay)34


Water!!!

Sun Light

Heating and Cooling

Acids

GEOLOGIC TIME

Erosion: Erosion: Creating Topography & SoilsCreating Topography & Soils

Disposing of the weathered debris atDisposing of the weathered debris at the margins of continentsthe margins of continents

Exposing different rocks & resourcesExposing different rocks & resources

35

An example from Central Texas

Sun City &Lake Georgetown

Erosion in Williamson County TodayErosion in Williamson County Today

More rock erodedMore rock eroded than remains!than remains!

36

Land surface today

Summary: The fate of all rocks at the earth’s surface

The Fate of All Rocks at the Earth’sThe Fate of All Rocks at the Earth’s Surface: Surface:

Destruction by Weathering & ErosionDestruction by Weathering & Erosion

Weathering of: Weathering of: Igneous Rocks=Clays & SandIgneous Rocks=Clays & Sand

Metamorphic Rocks=Clays & SandMetamorphic Rocks=Clays & Sand

Sedimentary Rocks=Clays, Sand, &Sedimentary Rocks=Clays, Sand, &Calcium SolutionsCalcium Solutions

37

The Fate of All Rocks at the Earth’sThe Fate of All Rocks at the Earth’s Surface: Surface:

Destruction by Weathering & ErosionDestruction by Weathering & Erosion

Erosion: Erosion: Moving weathered debris to theMoving weathered debris to the oceans at continental margins:oceans at continental margins: Clays, Sand and Calcium SolutionsClays, Sand and Calcium Solutions38

Erosional debris broughtto the Indian Ocean by theLimpopo and Zambezi rivers

Thick erosional debris deposited in the ocean at the continental margin is called a geosyncline

How thick is the sedimentary debris in a geosyncline?

Geosyncline Debris Thicknesses

Sea Level

Continental Crust

Oceanic Crust; 5 miles thick

Ocean 3 miles deep

Debris thickness = 3 miles (15,000 feet) if we just fill the ocean

How thick is the river debris?

Let’s look at the Niger River Debris

Niger River Delta: Geological Cross Section

The top of the oceanic crust has been depressed from 3 miles deep to 8 miles deep! This huge debris mass is called a geosyncline

Ocean3 miles deep

Niger Geosynclinal debris12, 000 meters = 40,000 feet= 8 miles thick

Let’s look at the Gulf of Mexico geosyncline as a well known example of a geosyncline

Example of a Geosyncline:Gulf of Mexico

1. Integration of the debris of several rivers

Modern Sediment

Accumulations

Swamp Muds

Shallow water Sands

Deep water Muds

2. Accumulation of thick layers of debris

New Orleans

Subsurface Cross Sections Gulf of Mexico Geosyncline

Austin

Sun City

Gulf of Mexico Geosyncline

MatureSourceRocks

SandstoneReservoirRocks

3. Accumulation of thick layers of debris

65,

00

0 fe

et t

hic

k Shale SourceRocks

Gulf ofMexico

New Orleans


Sun City


SourceRocks

MatureSourceRocks

4. Expulsion & Up-dip Migration of gas first, then oil, & finally gas

Gas

Gas

OilFinally, Trapping of Migrating Oil & Gas

New Orleans


Sun City


Muds in bays &

swamps

Sands at b

each & shelf

Sands & Muds m

ixed

Deep water Muds

5. Trapping of Migrating Oil & Gas

The Initial, Soft SedimentsNow a cross section of these sediments converted into Rocks



Shales

Sandstone re

servoirs

Sandstone & Shales

4. Trapping of Migrating Oil & GasNow a map of these sediments converted into Rocks

Star=Trap

Source shales

Lignite and Coal

Reservoir Rocks

Mixed Source &

Reservoir Rocks

Source Rocks

Limestones

5. Trapping of Migrating Oil & Gas

Conclusion: Geosynclines are primary sites for the accumulation of oil & gas

What is the “fate” of all geosynclines?

IllinoisIllinois OhioOhio PennsylvaniaPennsylvania VirginiaVirginia

Mountain Building: Crushing& melting of the geosyncline

Appalachian Example

Flat LimestonesFlat Limestones Gently dippingGently dippingSands & ShalesSands & Shales

FoldedFoldedSands &Sands &ShalesShales

Crushed &Crushed &MeltedMeltedGeosynclinalGeosynclinalRocks form aRocks form aMountains rangeMountains rangeFuture MountainsFuture Mountains

welded ontowelded onto continentcontinent

Now let’s apply what we’ve learned to Africa

Weathering is destroying the continent and erosion is moving the debris to the oceans atthe continental margins

The major and minor rivers of Africa that move debris to the continental margins

Today’s African geosynclines

Tropical Climate Zone

Remember: No world nation or sustained religion has ever developed in the TropicsWhat is the fate of all geosynclines?

The Big Rivers create thick deposits ofsand and mud called a geosynclines in the oceans at their deltas

Building a newMountain Range by melting & crushing of the sediments in the geosyncline

The Fate of Every Geosyncline: Mountain Building

Crushing and Melting a Geosyncline

Building a newMountain Range by melting & crushing

Collision of an Oceanic Plate with a Continental Plate

Mountain BuildingOriginal Geosyncline

ContinentalCrust

OceanicCrust

Ocean

ThickSediments

Thick debris accumulation at the margin of the continent

Note the dislocation of the contact between the Oceanic & and Continental Crust

When the Geosyncline exceeds a critical thickness, here’s what happens!

Melting of a geosyncline

Hot molten magma from the mantel rocks

Mountain BuildingEarly Stage: Geosyncline being crushing &

partially melting formingBasalt, Granite, & Rhyolite

BasaltGranite

OceanicCrust

ContinentalCrust

Heat from colliding crustal plates melts the base of the Oceanic crust and the “face” of the Continental crust

And then!!!!

Mountain BuildingBasaltic Island Arc and Granite Strato

VolcanoesBasalticIslandArc

RhyoliteStrato Volcano

A chain of volcanoes erupts: transferring material up through the sediments of the Geosyncline

And finallyGeosynclinal deposits being melting and welded back into the continent

Mountain BuildingGeosyncline Melted and Crushed

Welded ontocontinent

New mountain Range

The Geosyncline is welded onto the continent forming a new mountain range, and thus RENEWING the eroded continental land mass

What would happen if the continents were not renewed periodically?

The continents would be eroded down to slightly below sea level!

What would happen if the continents were not renewed periodically?

A Worldwide Ocean! No land: no plants, no animals, no us

In addition to renewing the continents, mountain building brings metallic ores, coal, and oil deposits to or near the surface

Mountain BuildingGeosyncline Melted and Crushed

Welded ontocontinent

New mountain Range

MetalsDistilled here

Metallic OresDeposited Here

Coal formed here

Modern Geosynclines of the Eurasia

NileNile

IndusIndus

From: Hammond Atlas, 1972From: Hammond Atlas, 1972

GangesGanges

YellowYellowYangtze Yangtze

Tigris Tigris Euphrates Euphrates

Nile Nile

Modern Geosynclines of the Eurasia

Potential Oil Sources and Future Mountains

Now back to Africa and the country of Tanzania

Regional View of Southern Africa

Zimbabwe

Tanzania

Ruvuma River

Tanzania

Ruvuma River

life long learning: fall 2012 vagabonds tramp eastern africa session three “vagabonds tramp...

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