1. Life Long Learning: Fall 2012 Vagabonds Tramp Eastern Africa Session 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 20 th century

2. Five Amazing Geological Discoveries of the Second Half of the 20 th Century 2. Continental Drift 3. Absolute Age Dating 4. Paleo-magnetics 5. 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 20 th century 1. Oceanic Crust

3. 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

4. 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 power 1. Continental drift and plate tectonic put Eurasia in the ideal location for early farming empires 2. 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?

5. Tropics Northern Temperate Zone Southern Temperate Zone What we’ll try to get you to believe in the next 3 weeks First Empires (farming major river flood plains) Green hills lands with Fe and Coal (invade farming lands) Where did the world-wide religions originate? Judaism Hinduism Confucianism Buddhism Christianity Mohammedism Conclusions: Geological events that shape human history are; Continental drift Plate tectonics Absolute age dating Paleo-magnetics Natural 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

6. Tropics Northern Temperate Zone Southern Temperate Zone What we’ll try to get you to believe in the next 3 weeks First Empires (farming major river flood plains) Green hills lands with Fe and Coal (invade farming lands) Where are the greatest concentrations of Iron & Coal? Judaism Hinduism Confucianism Buddhism Christianity Mohammedism Conclusions: Geological events that shape human history are; Continental drift Plate tectonics Absolute age dating Paleo-magnetics Natural resources of farm land, iron, coal, and oil Now let’s see if this can be applied to the country of Zimbabwe

7. Course definition of eastern Africa Focus on Zimbabwe Tropics What rocks are at the surface in Zimbabwe?

9. Geologic Map of Africa Shows the age of rocks at the surface Zimbabwe 500 million year old rocks at the surface Tropics

10. 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

11. Zimbabwe Tropics

12. Zimbabwe Tropics

13. Zambezi River Limpopo River Tropics Zimbabwe

14. River drainage divide Conclusion: No major river flood plains But let’s look at the topographic map

15. Limpopo River Zambezi River Zimbabwe Tropics What are the rocks like at the surface in Zimbabwe?

16. Very complex geology What are the archeological historic ages & the geological ages of geology? Geological Map of Zimbabwe Geologic 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

17. Conclusion: very complex geology Geological Map of Zimbabwe Geologic Maps show age and rock type at the surface if all soil & vegetation were removed Major river drainage divide line What are the geological ages of the rocks here?

18. Geologic Ages of Historic Time Iron, Coal, Petroleum, & Uranium Age 1950 to Present Iron, Coal, & Oil Age 1900 to 1950 AD Iron & Coal: Industrial Age 1700 to 1830 AD Iron & Coal: Renaissance 1450 to 1700 AD Iron & Coal: Middle Ages 470 to 1450 AD Iron Age 2 Rome to 470 AD 750 BCE 750 BCE Iron Age 1 Greece 1400 to 750 BCE Bronze Age 3300 to 1400 BCE Copper Age 3300 to 3000 BCE Stone Age (end of Ice Age) 70,000 to 3300 BCE Copper, tin, arsenic, & zinc Flint & Obsidian Iron Age Iron-Coal Age Iron, Coal, Oil Age Now the geologic ages of the 4.8 billion year old Earth Large scale Farming

19. Geologic Time: 4.8 Billion Years Pre-Cambrian 570 million to 4.9 billion years ago Age of most rocks at the surface in Zimbabwe Very old, may have metal ores What are the natural resources of Zimbabwe, is there farm-land, iron, and coal in Zimbabwe?

20. The natural resources of southern Africa Focus on Zimbabwe Coal Iron

21. 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?

22. Google-Earth: Southern Africa Zimbabwe Limpopo River Zambezi River Carving Landscapes (topography) Destruction of the Continental Crust Focus on possible farming areas in Zimbabwe

23. Focus on possible farming areas in Zimbabwe Focus on this province

24. 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

25. Focus on this province The regional view and another possible area of farming

26. 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?

27. What geologic processes impact today Zimbabwe?

28. Carving Landscapes (topography) Destruction of the Continental Crust Geologic Processes Weathering & Erosion Destruction of rocks which creates soil, rock debris, & topography 28

29. 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

30. WEATHERING: How is it done? Water!!! Sun Light Heating and Cooling Natural Acids TIME TIME TIME 30

31. WEATHERING: How is it done? Water!!! Abrasion by: Falling Rain Flowing Streams and Rivers 31

32. WEATHERING: How is it done? Water!!! Sun Light (radiation) 32

33. WEATHERING: How is it done? Water!!! Sun Light Heating and Cooling daily expansion and contraction 33

34. WEATHERING: How is it done? Water Sun Light Heating and Cooling Natural Acids Acid Rain (natural) Humic Acid (plant decay) 34

35. WEATHERING: How is it done? Water!!! Sun Light Heating and Cooling Acids GEOLOGIC TIME Erosion: Creating Topography & Soils Disposing of the weathered debris at the margins of continents Exposing different rocks & resources 35 An example from Central Texas

36. Sun City & Lake Georgetown Erosion in Williamson County Today More rock eroded than remains! than remains! 36 Land surface today Summary: The fate of all rocks at the earth’s surface

37. The Fate of All Rocks at the Earth’s Surface: Destruction by Weathering & Erosion Weathering of: Igneous Rocks=Clays & Sand Metamorphic Rocks=Clays & Sand Sedimentary Rocks=Clays, Sand, & Calcium Solutions 37

38. The Fate of All Rocks at the Earth’s Surface: Surface: Destruction by Weathering & Erosion Erosion: Moving weathered debris to the oceans at continental margins: Clays, Sand and Calcium Solutions 38

39. Erosional debris brought to the Indian Ocean by the Limpopo 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?

40. 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

41. 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 Ocean 3 miles deep Niger Geosynclinal debris 12, 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

42. Example of a Geosyncline: Gulf of Mexico 1. Integration of the debris of several rivers M o d e r n S e d i m e n t A c c u m u l a t i o n s Swamp Muds Shallow water Sands Deep water Muds 2. Accumulation of thick layers of debris

43. New Orleans Subsurface Cross Sections Gulf of Mexico Geosyncline Austin Sun City Gulf of Mexico Geosyncline Mature Source Rocks Sandstone Reservoir Rocks 3. Accumulation of thick layers of debris 65,000 feet thick Shale Source Rocks Gulf of Mexico

44. New Orleans Subsurface Cross Sections Gulf of Mexico Geosyncline Sun City Gulf of Mexico Geosyncline Source Rocks Mature Source Rocks 4. Expulsion & Up-dip Migration of gas first, then oil, & finally gas Gas Oil Finally, Trapping of Migrating Oil & Gas

45. New Orleans Subsurface Cross Sections Gulf of Mexico Geosyncline Sun City Gulf of Mexico Geosyncline Muds in bays & swamps Sands at beach & shelf Sands & Muds mixed Deep water Muds 5. Trapping of Migrating Oil & Gas The Initial, Soft Sediments Now a cross section of these sediments converted into Rocks

46. Subsurface Cross Sections Gulf of Mexico Geosyncline Gulf of Mexico Geosyncline Shales Sandstone reservoirs Sandstone & Shales 4. Trapping of Migrating Oil & Gas Now a map of these sediments converted into Rocks Star=Trap Source shales

47. 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?

48. IllinoisOhio Pennsylvania Virginia M ountain Building: Crushing & melting of the geosyncline Appalachian Example Flat Limestones Gently dipping Sands & Shales Folded Sands & Shales Crushed & MeltedGeosynclinal Rocks form a Mountains range Future Mountains welded onto continent Now let’s apply what we’ve learned to Africa

49. Weathering is destroying the continent and erosion is moving the debris to the oceans at the continental margins The major and minor rivers of Africa that move debris to the continental margins

50. Today’s African geosynclines Tropical Climate Zone Remember: No world nation or sustained religion has ever developed in the Tropics What is the fate of all geosynclines? The Big Rivers create thick deposits of sand and mud called a geosynclines in the oceans at their deltas

51. Building a new Mountain Range by melting & crushing of the sediments in the geosyncline The Fate of Every Geosyncline: Mountain Building Crushing and Melting a Geosyncline

52. Building a new Mountain Range by melting & crushing Collision of an Oceanic Plate with a Continental Plate

53. Mountain Building Original Geosyncline Continental Crust Oceanic Crust Ocean Thick Sediments 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

54. Mountain Building Early Stage: Geosyncline being crushing & partially melting forming Basalt, Granite, & Rhyolite Basalt Granite Oceanic Crust Continental Crust Heat from colliding crustal plates melts the base of the Oceanic crust and the “face” of the Continental crust And then!!!!

55. Mountain Building Basaltic Island Arc and Granite Strato Volcanoes Basaltic Island Arc Rhyolite Strato Volcano A chain of volcanoes erupts: transferring material up through the sediments of the Geosyncline And finally Geosynclinal deposits being melting and welded back into the continent

56. Mountain Building Geosyncline Melted and Crushed Welded onto continent 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?

57. 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

58. Mountain Building Geosyncline Melted and Crushed Welded onto continent New mountain Range Metals Distilled here Metallic Ores Deposited Here Coal formed here Modern Geosynclines of the Eurasia

59. Nile Indus From: Hammond Atlas, 1972 Ganges YellowYangtze TigrisEuphrates Nile Modern Geosynclines of the Eurasia Potential Oil Sources and Future Mountains Now back to Africa and the country of Tanzania

60. Regional View of Southern Africa Zimbabwe Tanzania Ruvuma River

61. Tanzania Ruvuma River