Transcript File - GEOLOGY ROCKS!

Life Long Learning: Fall 2012
First, remember the amazing geological
discoveries of the last half of the 20th century
Vagabonds Tramp Eastern Africa
Session Three
Let’s recall from last week that the great
nations of human history were located in the
Northern Temperate Zone, that they had
“Vagabonds Tramp through Eastern Africa: where the
extensive
farmland, plus iron and coal
unique geology of the East African Rifts produced the
advent
of the
human what
species we’re
and the Nile
flood plain
Then
let’s
apply
learned
to
shaped the beginning of human history”
the country of Zimbabwe
Five Amazing Geological Discoveries
of the Second Half of the 20th Century
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
2. Continental Drift
3. Absolute Age Dating
4. Paleo-magnetics
5. Plate Tectonics
Mid Ocean “ridge”
Continental Crust
African Plate:
African Continental crust
plus surrounding oceanic crust
Oceanic Crust
Last week we also showed the location
of the world’s great nations
Conclusions on what is required for a land to become a world power
What
we’ll try todrift
getand
youplate
to believe
in the
nextin5the
weeks
1. Continental
tectonic put
Eurasia
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
Northern Temperate Zone
Where did the world-wide religions originate?
Tropics
Southern Temperate Zone
First Empires (farming major river flood plains)
Green hills lands with Fe and Coal (invade farming lands)
What
we’ll try
to get
you
to
believe
the next
3 weeks
Then
let’s
see
if this
can
be in
applied
to
the
Conclusions:
Geological
events
that
shape
human
history
are;
Continental drift
country of Zimbabwe
Plate tectonics
But first
let’s
where
concentrations
Absolute
age
dating the greatest
Where
did
thesee
world-wide
religions
originate?
Paleo-magnetics
of iron and coal are located
Natural resources of farm land, iron, coal, and oil
Northern Temperate Zone
Tropics
Southern Temperate Zone
Judaism
Hinduism
Confucianism
Buddhism
First Empires (farming major river flood plains)
Green hills lands with Fe and Coal (invade farming lands)
Christianity
Mohammedism
What we’ll
to get
believe
the next 3to
weeks
Now
let’strysee
if you
thistocan
beinapplied
the
country of Zimbabwe
Where are the greatest concentrations of Iron & Coal?
Northern Temperate Zone
Conclusions: GeologicalTropics
events that shape human history
are;
Judaism
Continental drift
Hinduism
Plate tectonics
Confucianism
Absolute age dating
Buddhism
Paleo-magnetics Southern Temperate Zone
Christianity
Natural resources of farm land, iron, coal, and oil
Mohammedism
First Empires (farming major river flood plains)
Green hills lands with Fe and Coal (invade farming lands)
Focus on Zimbabwe
Tropics
Course
definition
of eastern
Africa
What rocks are at the surface in Zimbabwe?
Geologic Map of Africa
Shows the age of rocks at the surface
Tropics
Zimbabwe
500 million year old rocks at the surface
Geologic Map of Southern Africa
Focus on Zimbabwe
Tropics
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
Zimbabwe
Zambezi River
Zimbabwe
Tropics
Limpopo River
But let’s look at the topographic map
River drainage divide
Conclusion: No major river flood plains
Zambezi River
Zimbabwe
Tropics
What are the rocks like at the
River
surface inLimpopo
Zimbabwe?
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 archeological historic ages &
the geological ages of geology?
Note that the Limpopo drainage has
Verythecomplex
geology
most very old
rocks
Geologic Ages of Historic Time
Iron, Coal,
Oil Age
Now
Iron, Coal, Petroleum, & Uranium Age 1950 to Present
the
geologic
ages of the 4.8 1900
billion
year
Iron,
Coal, & Oil Age
to 1950
AD
old Earth
Iron-Coal
Age
Iron & Coal: Industrial Age
Iron & Coal: Renaissance
1700 to 1830 AD
1450 to 1700 AD
Iron & Coal: Middle Ages
Iron Age
Copper, tin,
arsenic, & zinc
Flint & Obsidian
470 to 1450 AD
Iron Age 2 Rome
to 470 AD
750 BCE
Iron Age 1 Greece
1400 to 750 BCE
Bronze Age Large scale Farming 3300 to 1400 BCE
Copper Age
3300 to 3000 BCE
Stone Age (end of Ice Age) 70,000 to 3300 BCE
Geologic Time: 4.8 Billion Years
What are the natural resources of Zimbabwe,
is there farm-land, iron, and coal in Zimbabwe?
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
The natural resources of southern Africa
Coal
Iron
Focus on Zimbabwe
The natural resources of Zimbabwe
Farmland
Tropics
Grazing land
Conclusions:
Even thoughtshow
Zimbabwe
is in
What
does Google-earth
us about
thefarm
Tropics,
is high enough
be largely
the
anditgrazing
land oftoZimbabwe?
above jungle and it has significant farm land
plus iron and coal that could support the
development of a important nation.
Google-Earth: Southern Africa
Focus on possible farming areas in Zimbabwe
Zambezi River
Zimbabwe
Limpopo River
Carving Landscapes (topography)
Destruction of the Continental Crust
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
What geological processes created
this topography of Zimbabwe?
Carving Landscapes (topography)
Destruction of the Continental Crust
Geologic Processes
Weathering & 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 TIME
30
WEATHERING: How is it done?
Water!!!
Abrasion by:
Falling Rain
Flowing Streams and Rivers
31
WEATHERING: How is it done?
Water!!!
Sun Light (radiation)
32
WEATHERING: How is it done?
Water!!!
Sun Light
Heating and Cooling
daily expansion and contraction
33
WEATHERING: How is it done?
Water
Sun Light
Heating and Cooling
Natural Acids
Acid Rain (natural)
Humic Acid (plant decay)
34
WEATHERING: How is it done?
Water!!!
Sun Light
Erosion:
Heating and Cooling
An Creating
example
from Central
Texas
Topography
& Soils
Acids
Exposing different rocks & resources
Disposing
of the weathered
GEOLOGIC
TIME debris at
the margins of continents
35
Erosion in Williamson County Today
More rock eroded
than remains!
Land surface today
Sun City &
Lake Georgetown
Summary: The fate of all rocks at the
earth’s surface
36
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
The Fate of All Rocks at the Earth’s
Surface:
Destruction by Weathering & Erosion
Erosion:
Moving weathered debris to the
oceans at continental margins:
Clays, Sand and Calcium Solutions
38
Thick erosional debris deposited
in the ocean at the continental
margin is called a geosyncline
Erosional debris brought
How thick is the sedimentary debris
to the Indian Ocean by the
in a geosyncline?
Limpopo and Zambezi rivers
Geosyncline Debris Thicknesses
Debris thickness = 3 miles (15,000 feet) if we just fill the ocean
Ocean 3 miles deep
Sea Level
Continental Crust
Oceanic Crust; 5 miles thick
How thick is the river debris?
Let’s look at the Niger River Debris
Niger River Delta: Geological Cross Section
Ocean
3 miles deep
12, 000 meters
= 40,000 feet
= 8 miles thick
Niger Geosynclinal debris
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
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
2. Accumulation of thick layers of debris
Sandstone
Reservoir
Rocks
Gulf of Mexico
Geosyncline
65,000 feet thick
Subsurface Cross Sections
Gulf of Mexico Geosyncline
Shale
Source
Rocks
Gulf of
Mexico
Mature
Source
Rocks
3. Accumulation of thick layers of debris
Subsurface Cross Sections
Gulf of Mexico Geosyncline
Source
Rocks
Finally, Trapping of Migrating Oil & Gas
Gulf of Mexico
Geosyncline
Mature
Source
Rocks
4. Expulsion & Up-dip Migration of
gas first, then oil, & finally gas
Subsurface Cross Sections
Gulf of Mexico Geosyncline
of Mexico
NowGulf
aThe
cross
section
of
these
sediments
Initial, Soft Sediments
Geosyncline
converted into Rocks
5. Trapping of Migrating Oil & Gas
Subsurface Cross Sections
Gulf of Mexico Geosyncline
Star=TrapGulf of Mexico
Geosyncline
Now a map of these sediments
4. Trapping of Migrating Oil & Gas
converted into Rocks
5. Trapping of Migrating Oil & Gas
Conclusion: Geosynclines are primary
sites for the accumulation of oil & gas
What is the “fate” of all geosynclines?
Mountain Building: Crushing
& melting of the geosyncline
Appalachian Example
Illinois
Flat Limestones
Ohio
Pennsylvania
Folded
Sands &
Shales
Future Mountains
welded onto
continent
Virginia
Crushed &
Melted
Geosynclinal
Rocks form a
Mountains range
Now let’s apply what we’ve learned to Africa
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
Today’s African geosynclines
Tropical Climate Zone
The Big Rivers create thick deposits of
sand and mud called a geosynclines in
the oceans at their deltas
What is
Remember: No world nation or
sustained religion has ever
thedeveloped
fate ofinall
thegeosynclines?
Tropics
The Fate of Every Geosyncline:
Mountain Building
Crushing and Melting a
Geosyncline
Building a new
Mountain Range by
melting & crushing
of the sediments in
the geosyncline
Collision of an Oceanic Plate
with a Continental Plate
Building a new
Mountain Range by
melting & crushing
Mountain
Building
Melting of a geosyncline
Original Geosyncline
When the Geosyncline exceeds a
critical thickness, here’s what happens!
Ocean
Oceanic
Crust
Hot molten
magma from
the mantel rocks
Thick
Sediments
Continental
Crust
Note the dislocation of the
contact between the Oceanic &
and Continental Crust
Thick debris accumulation at the margin
of the continent
Mountain Building
Early Stage: Geosyncline being crushing &
partially melting forming
Basalt, Granite, & Rhyolite
And then!!!!
Oceanic
Crust
Continental
Crust
Basalt
Granite
Heat from colliding crustal plates
melts the base of the Oceanic crust
and the “face” of the Continental crust
Mountain Building
Basaltic Island Arc and Granite Strato
Volcanoes
Basaltic
Island
Arc
Geosynclinal deposits
being melting and
welded back into
the continent
Rhyolite
Strato Volcano
And finally
A chain of volcanoes erupts: transferring
material up through the sediments
of the Geosyncline
Mountain Building
Geosyncline Melted and Crushed
New mountain
Range
Welded onto
What would happen if continent
the continents
were not renewed periodically?
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
A Worldwide
Ocean!
down to
slightly below
sea level!
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 Building
Geosyncline Melted and Crushed
Coal formed here
New mountain
Range
Welded onto
continent
Metallic Ores
Deposited Here
Metals
Distilled here
Modern Geosynclines of the
Eurasia
Modern Geosynclines of the
Eurasia
Yellow
Yangtze
Tigris
Euphrates
Indus
Ganges
Now Nile
back to Africa and the country of Tanzania
Nile
From: Hammond Atlas, 1972
Potential Oil Sources and
Future Mountains
Regional View of Southern Africa
Tanzania
Ruvuma
River
Zimbabwe
Tanzania
Ruvuma River