Transcript File - Vagabond Geology

Earth’s crammed with heaven,
And every common bush afire with God;
But only he who sees takes off his shoes,
The rest sit round it and pluck blackberries.
Elizabeth Barrett Browning
The Phantom Science: How Geology Created
Geological
Resources
the Amazing
Natural Resources
of Central Texas
Don Beaumont
Texas Master Naturalists
Land of Good Water Chapter
March 23, 2010
Geological Resources
Rivers and River Flood Plains
Farming soils
Hills and Valleys
Grazing & farming soils
How does geology provide these resources?
Rivers, lakes, & ground water
Water
Rocks
Iron, coal, oil & gas, and uranium
How does geology create natural resources?
Four geological processes
1. Continental drift
2. Plate tectonics
3. Weathering
4. Erosion
Five
geological
events
Four
Geological Processes
1. Continental Drift positions the continents
2. Plate
Tectonics
shapes the continents
1.
Continental
Drift
3. Weathering makes soils
4. Erosion creates topography & exposes ores
5. Glaciers determine human distribution
Continental Drift
The slow movement of the crustal plates
over the face of the earth
Continental Drift:
Last 250 million years
Present Day
Four Geological Processes
2. Plate Tectonics
250 million years ago
http://schools.techno.ru/sch518/koridor/geograf
/detrab/Tektonika/litosfera2.htm
2. Plate Tectonics
The deforming of continents
as they move & when they collide
Types of deformation:
warping = major river systems
crushing & melting = mountain ranges
2. Plate Tectonics
Plate motion = warping = major rivers
Plate collision = crushing & melting =
mountain ranges
Four Geological Processes
3. Weathering
Down warp
Four Geological Processes
3. Weathering
The natural destruction of the
surface of the earth’s rocky crust
Weathering
produces
rock debris:
Bed Rock
(soils)
of Texas
1. Clays combine with decaying organic
matter to make soils
2. Clays, Ca solutions, & sand are carried
by rivers to the continental margins
Bed Rock (soils) of Texas
Each rock (color) weathers into a unique soil
Vegetational Areas of Texas
Grand Prairies
Blackland
Prairies
Four Geological Processes
4. Erosion
Williamson
County
Edwards Plateau
Similar soils produce these vegetational areas
4. Erosion
The transport of weathered debris
by water to the continental margins
Erosion:
1. creates topography
2. exposes Topography
ores and oil at or
Erosion Created
ofnear
Texas
the earth’s surface
3. creates river flood plains
Erosion Created Topography of Texas
Plateaus
Erosion Exposed Natural Resources thatCoastal
Shaped
Plains
& Flood Plains
Human History
Erosion Exposed Natural Resources that Shaped
Human History
Flood Plains Created by Rivers
Carrying Clays & Sand to the Ocean
Iron , coal , and
oil exposed by
erosion in Texas
Flood Plains Created by Rivers
Carrying Clays & Sand to the Ocean
Five Geologic Events that Shaped
Human History
How does geology create natural resources?
Four geological processes
1. Continental drift
2. Plate tectonics
3. Weathering
4. Erosion
Five geological events that shaped
the history of Texas
1. Continental Drift positions our continent
2. Plate Tectonics shapes our continent
3. Weathering makes our soils
4. Erosion creates our topography & exposes our ores
5. Glaciers determine human distribution
Five Geologic Events that Shaped
Human History
Continental Drift positioned Central Texas:
Determining
the migration
patharrive
of humans
A.
determining when
humans would
B. creates two limestones rocks: aquifers & springs
How has continental drift shaped
human history?
Next:
How
Plate
Tectonics
shaped
Eastern
Western
human
history?
Hemisphere
Hemisphere
Created the Western and Eastern Hemispheres
Critical to the migration of humans out of Africa
Five Geologic Events that Shaped
Human History
1.
Continental Drift shapes & positions the continents
Migration path of humans created
2. Plate Tectonics shapes the continents:
A. Determines location of early nations
B. Creates new rivers in Texas & muddy
limestones = good farming soils
C. Creates sandstone/shale rocks
in Texas with coal
Geological Event # 2: 6000 mile mountain
range created by Africa & India colliding
with Eurasia
Yellow
Yangtze
Nile
Tigris
Euphrates
Indus
Ganges
Conclusions: Early civilization grew in:
Ideal trend
the early
development
1. thefor
Northern
Temperate
Zone
majorfarming
river floodcivilizations
plains
of large2.scale
Why no major nations in Texas?
Flood Plains Created by Rivers
Carrying Clays & Sand to the Ocean
Area adversely affected by the melting of
the most recent continental glacier:
1. flooded with debris choked melt-water
2. hostile cold climate
Plate Tectonics creates two limestones with
aquifers, caves, and springs in Central Texas
Why no major nations in this
Temperate Zone Flood Plain?
Five Geologic Events that Shaped
Human History
Continental Drift positioned Central Texas:
A. determining when humans would arrive
B. Plate Tectonics creates two limestones with
aquifers, caves, and springs in Central Texas
Mid-Cretaceous: 90 million years ago
Edwards Limestone Time
So what is a limestone?
Shallow water Edwards limestones forming in Texas
Beach in southern Oklahoma
No nearby rivers with mud & silt = pure limestone
Area of
Edwards
Limestone
Tropical Climate Zone
Typical Limestones in Sun City, Texas
A dense limestone,
no obvious shells,
made of lime mud
A limestone reef composed
of rudists and many other
shell fish.
Just what is a limestone?
Limestones are Rocks
Made of Sea Shells
Back to the
Edwards Limestone
Limestones
(CaCO3)formed
in an ancient,
tropical,
island paradise
Mineral:
calcite
Shells & Shell Debris
(majority marine)
Paleogeographic Map: Gulf of Mexico
Sun City
Texas
Florida
Extent of the Edwards Limestone
A modern example:
the Great Barrier Reef of Australia
The Great Barrier Reef of Australia
Shallow Ocean Environments = Limestone Facies
A modern equivalent
of the Edwards
Shallow Ocean Environments = Limestone Facies
Reef & Reef Mound
Shells
A Typical Limestone Formation
Shell Debris
Shell mud
Composite
Cartoon of a Typical Limestone Formation
Remember the Rudist Reef Rocks?
Each bed contains one or more environments
Scale: beds from inches thick to 10’s of feet thick
Remember the Rudist Reef Rocks?
What is a rudist and
how do they form reefs?
Rudists are Horn-shaped Sea Shells
Rudists grow in colonies (reefs)
Rudist forming Reefs: Typical of Cretaceous Limestones
Rudist shells are very fragile so they
are often destroyed by weathering
leaving a cone shaped hole
Edwards Limestone has thick (up to 50 feet thick) layers (beds)
composed of RUDIST REEFS and REEF DEBRIS MOUNDS
A Rudist Reef Rock Outcrop
The cavities in reef limestones often
make:
1.good aquifers,
2. springs,
3. caves.
Each hole was occupied by
a rudist shell fish
Lower Cretaceous Edwards Limestone Reef
Blue Hole City Park
Edwards Limestone Reefs and Caves
I-35 Access Road Cut at Leander Road
Reef
water filled aquifer
A Cave in a Limestone Layer
Cave formed by ground water solution
of the Limestone
Let’s look at a cartoon of a limestone cave
Block Diagram of Mammoth Cave
Back to the Five Geologic Events that Shaped
Human History (esp. in Texas)
Five Geologic Events that Shaped
Human History
1.
Continental Drift shapes & positions the continents
Migration path of humans created
2. Plate Tectonics shapes the continents:
How are continents shaped?
1. mountain building
2. broad down-warping
3. broad up-warping
Creating a Geologic Model
for Mountain Building
Mountain Building:
When two crustal plates collide
Crustal Plates: Both Oceanic & Continental
Continents are carried on their crustal plate
Mountain Building
Plate Tectonic Theory
Three Types of Plate Collisions
Mountains
Continent
Oceanic
Plate
Oceanic
Plate
Continent
Continent
Oceanic
Plate