The Phantom Science: How Geology Created the Amazing Natural Resources of Central Texas

Don Beaumont

Texas Master NaturalistsLand of Good Water Chapter March 23, 2010

Geological Resources

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

Geological Resources

Rivers and River Flood PlainsFarming soils

Hills and ValleysGrazing & farming soils

Rivers, lakes, & ground waterWater

RocksIron, coal, oil & gas, and uranium

How does geology provide these resources?

How does geology create natural resources?

Four geological processes

Five geological events

1. Continental drift2. Plate tectonics3. Weathering 4. Erosion

1. Continental Drift positions the continents2. Plate Tectonics shapes the continents

3. Weathering makes soils

5. Glaciers determine human distribution4. Erosion creates topography & exposes ores

Four Geological Processes 1. Continental Drift

Continental Drift

The slow movement of the crustal plates over the face of the earth

http://schools.techno.ru/sch518/koridor/geograf/detrab/Tektonika/litosfera2.htm

Continental Drift: Last 250 million years

Present Day

250 million years ago

Four Geological Processes 2. Plate Tectonics

2. Plate Tectonics

The deforming of continents as they move & when they collide

Types of deformation:warping = major river systemscrushing & melting = mountain ranges

Down warp

Crus

hing

& m

eltin

g

2. Plate TectonicsPlate motion = warping = major rivers Plate collision = crushing & melting =

mountain ranges

Four Geological Processes 3. Weathering

The natural destruction of the surface of the earth’s rocky crust

Weathering produces rock debris:1. Clays combine with decaying organic

matter to make soils2. Clays, Ca solutions, & sand are carried

by rivers to the continental margins

Four Geological Processes 3. Weathering

Bed Rock (soils) of Texas

Bed Rock (soils) of Texas

Each rock (color) weathers into a unique soil

Grand PrairiesGrand Prairies

Edwards PlateauEdwards Plateau

BlacklandBlacklandPrairiesPrairies

Vegetational Areas of TexasVegetational Areas of Texas

Similar soils produce these vegetational areasSimilar soils produce these vegetational areas

WilliamsonCounty

Four Geological Processes 4. Erosion

4. Erosion

The transport of weathered debrisby water to the continental margins

Erosion:1. creates topography2. exposes ores and oil at or near

the earth’s surface3. creates river flood plains

Erosion Created Topography of Texas

Erosion Created Topography of Texas

Mountains

Plateaus

Coastal Plains& Flood Plains

Erosion Exposed Natural Resources that Shaped Human History

Iron , coal , and oil exposed by erosion in Texas

Erosion Exposed Natural Resources that Shaped Human History

Flood Plains Created by Rivers Carrying Clays & Sand to the Ocean

Major river floodplains

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

Five geological events that shaped the history of Texas

1. Continental drift2. Plate tectonics3. Weathering 4. Erosion

1. Continental Drift positions our continent2. Plate Tectonics shapes our continent

3. Weathering makes our soils

5. Glaciers determine human distribution4. Erosion creates our topography & exposes our ores

1. Continental Drift positions our continent

Five Geologic Events that Shaped Human History

Continental Drift positioned Central Texas:A. determining when humans would arrive

B. creates two limestones rocks: aquifers & springs

Determining the migration path of humans

WesternHemisphere

EasternHemisphere

How has continental drift shaped human history?

Created the Western and Eastern Hemispheres

Critical to the migration of humans out of Africa

Next: How Plate Tectonics shaped human history?

Five Geologic Events that Shaped Human History

1. Continental Drift shapes & positions the continentsMigration 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

2. Plate Tectonics shapes the continents: A. Determines location of early nations

Geological Event # 2: 6000 mile mountain range created by Africa & India colliding with Eurasia

Yellow

Yangtze

GangesTigrisEuphratesNile Indus

Ideal trend for the early development of large scale farming civilizations

Conclusions: Early civilization grew in: 1. the Northern Temperate Zone2. major river flood plains

Why no major nations in Texas?

Major river floodplains

Why no major nations in this Temperate Zone Flood Plain?

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-water2. hostile cold climate

Plate Tectonics creates two limestones with aquifers, caves, and springs in Central Texas

Five Geologic Events that Shaped Human History

Continental Drift positioned Central Texas:A. determining when humans would arriveB. Plate Tectonics creates two limestones with aquifers, caves, and springs in Central Texas

Mid-Cretaceous: 90 million years agoMid-Cretaceous: 90 million years ago Edwards Limestone TimeEdwards Limestone Time

Beach in southern OklahomaBeach in southern Oklahoma

So what is a limestone?So what is a limestone?

No nearby rivers with mud & silt = pure limestoneNo nearby rivers with mud & silt = pure limestone

Area ofEdwards Limestone

Shallow water Edwards limestones forming in TexasShallow water Edwards limestones forming in Texas

Tropical Climate Zone

Typical Limestones in Sun City, Texas

A dense limestone, no obvious shells, made of lime mud

Just what is a limestone?Just what is a limestone?

A limestone reef composed of rudists and many other shell fish.

Shells & Shell Debris (majority marine)

Limestones (CaCO3)Mineral: calcite

Limestones are Rocks Made of Sea Shells

Back to the Edwards Limestone formed in an ancient, tropical, island paradise

Paleogeographic Map: Gulf of Mexico

FloridaTexas

Sun City

Extent of the Edwards Limestone

A modern example: the Great Barrier Reef of Australia

The Great Barrier Reef of Australia

A modern equivalent of the Edwards

Great Barrier ReefShallow Ocean Environments = Limestone Facies

Shallow Ocean Environments = Limestone Facies

Reef & Reef Mound

Shells

Shell Debris

Shell mud

Composite

A Typical Limestone Formation

Cartoon of a Typical Limestone Formation

Scale: beds from inches thick to 10’s of feet thick

Each bed contains one or more environments

Remember the Rudist Reef Rocks?

Remember the Rudist Reef Rocks?

What is a rudist and how do they form reefs?

Rudist forming Reefs: Typical of Cretaceous Limestones

Edwards Limestone has thick (up to 50 feet thick) layers (beds) composed of RUDIST REEFS and REEF DEBRIS MOUNDS

Rudists are Horn-shaped Sea ShellsRudists grow in colonies (reefs)

Rudist shells are very fragile so they are often destroyed by weathering leaving a cone shaped hole

A Rudist Reef Rock Outcrop

Each hole was occupied by a rudist shell fish

The cavities in reef limestones often make:

1.good aquifers,2. springs,

3. caves.

Lower Cretaceous Edwards Limestone ReefBlue Hole City Park

Edwards Limestone Reefs and CavesI-35 Access Road Cut at Leander Road

Reef

water filled aquifer spring

A Cave in a Limestone LayerCave 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 continentsMigration path of humans created

2. Plate Tectonics shapes the continents:How are continents shaped?

1. mountain building2. broad down-warping3. broad up-warping

1. mountain building

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

Plate Collision

Mountain BuildingPlate Tectonic Theory

Three Types of Plate CollisionsContinent

ContinentMountains

OceanicPlate

Continent

OceanicPlateOceanic

Plate