Ch. 1 Dynamic and Evolving Earth ESCI 102 Spring 2005

Ch. 1 Dynamic and Evolving Earth

ESCI 102Spring 2005

Lec. 1 Review/Summary Questions

1)What are the five subsystems of Earth?

2)Are there any more details known about early Earth?

3)If everything in the universe is moving away from us, why is it that we are not the center of the universe?

4)How has Earth’s core stayed hot for so long?

Earth’s Interior Layers• Crust - 5-90 km

thick– continental

and oceanic• Mantle

– composed largely of peridotite

– dark, dense igneous rock

– rich in iron and magnesium

• Core– iron and a

small amount of nickel

Earth’s Interior Layers• Crust - 5-90 km

thick– continental

and oceanic• Mantle

– composed largely of peridotite

– dark, dense igneous rock

– rich in iron and magnesium

• Core– iron and a

small amount of nickel

• Lithosphere– solid upper

mantle and crust

• Asthenosphere– part of upper

mantle– behaves

plastically and slowly flows

Earth’s Interior Layers• Lithosphere

– solid upper mantle and crust

• Asthenosphere– part of upper

mantle– behaves plastically

and slowly flows

– broken into plates that move over the asthenosphere

Earth’s Crust

• continental (20-90 km thick)– density 2.7

g/cm3 – contains Si, Al

• oceanic (5-10 km thick)– density 3.0 g/cm3 – composed of basalt

Plate Tectonic Theory

• Lithosphere is broken into individual pieces called plates

• Plates move over the asthenosphere – as a result of underlying convection cells

Modern Plate Map


• at plate boundaries– volcanic activity occurs– earthquakes occur

• movement at plate boundaries – plates diverge– plates converge– plates slide sideways past each other


• types of plate boundaries

Transform

DivergentCont.-Cont.ConvergentCont.-Ocean

ConvergentOcean-oceanConvergent


influence on geological sciences:• revolutionary concept

– comparable to evolution

• provides a framework for – interpreting many aspects of Earth on a

global scale– relating many seemingly unrelated

phenomena– interpreting Earth history

Plate Tectonics and Earth Systems

• plate tectonics is driven by convection in the mantle

– and in turn drives mountain building – and associated igneous and

metamorphic activitySolid

Eart

hA

tmosp

here • arrangement of continents affects:

– solar heating and cooling, – and thus winds and weather systems

• rapid plate spreading and hot-spot activity may release volcanic carbon dioxide and affect global climate

Plate Tectonics and Earth Systems

• continental arrangement affects ocean currents

• rate of spreading affects volume of mid-oceanic ridges and hence sea level

• placement of continents contributes to the onset of ice agesH

ydro

sphere

Bio

sphere • movement of continents creates

corridors or barriers to migration, the creation of ecological niches, and transport of habitats into more or less favorable climates

Theory of Organic Evolution

• provides a framework for understanding the history of life

• Darwin’s On the Origin of Species by Means of Natural Selection, published in 1859

• revolutionized biology

Central Thesis of Evolution

• all present-day organisms – are related – descended from organisms that lived

during the past• Natural Selection is the mechanism

that accounts for evolution – results in the survival to reproductive

age of those organisms best adapted to their environment

History of Life

• Fossils are the remains or traces of once-living organisms– demonstrate that Earth has a history of

life– most compelling evidence in favor of

evolution

Geologic Time

• human perspective– seconds, hours, days, years

• ancient human history– hundreds or even thousands of years

• geologic history– millions, hundreds of millions, billions of

years

Geologic Time Scale• resulted from the work of many 19th

century geologists who – pieced together information from

numerous rock exposures– constructed a sequential chronology

based on changes in Earth’s biota through time

• the time scale was subsequently dated in years – using radiometric dating techniques

Geologic Time Scale

Uniformitarianism• Uniformitarianism is a cornerstone of

geology

– present-day processes have operated throughout time

– physical and chemical laws of nature have remained the same through time

• to interpret geologic events – we must first understand present-day

processes and their results

How Does the Study of Historical Geology Benefit Us?

• survival of the human species depends on understanding how Earth’s various subsystems work and interact– how we consume natural resources and interact with

the environment determines our ability to pass on this standard of living to the next generation

– our standard of living depends directly on our consumption of natural resources that formed millions and billions of years ago

• study what has happened in the past, on a global scale, to try and determine how our actions might affect the balance of subsystems in the future

Present

Note: Best data set available.

http://vishnu.glg.nau.edu/rcb/globaltext.html

Latest Precambrian / Early Paleozoic

Supercontinent Rodinia, centered about the south pole, breaks apart. North America (Laurentia), Baltica, and Siberia moved North.

Marine Invertebrates.

North America: arc on the south. Baltica and Siberia moved in from the SE.

Texas (505-570 Ma): Flat plain; remnants of eroded collisional belt (Llano). Shallow marine seas across much of Texas. Sandy sediment onshore, limestone offshore. Trilobites, brachiopods.http://vishnu.glg.nau.edu/rcb/globaltext.html

Latest Precambrian / Early Paleozoic

Supercontinent Rodinia continues to break apart. Pieces move north.

-Fish.-Glaciation.

North America: Numerous plates and continental blocks move in from the south and east. The Taconic arc collides, forming the Taconic orogeny.

Texas 438-505 Ma: Shallow marine seas across much of inland Texas. Warm-water limestone. Corals, brachiopods.http://vishnu.glg.nau.edu/rcb/globaltext.html

Middle / Late Paleozoic

Remains of Rodinia (Gondwana) move northward to collide with Laurasia -- creating the super continent Pangaea and the Tethys Ocean.

First land-plants.

Baltica collides with North America in the Caledonian-Acadian orogeny.

Texas 403-438 Ma: Shallow marine seas across much of west Texas - limestone. Corals, brachiopods.



Most drifting Rodinia blocks assembled into the super continent of Laurussia.

Amphibians. Fish really get going. Ferns.

Glaciation.

North America: Caledonian-Acadian orogeny marks assemblage of Laurussia. Gondwana closed in from the south. An arc formed along western North America.

Texas 360-408 Ma: shallow marine sandstones and limestones in west Texas. http://vishnu.glg.nau.edu/rcb/globaltext.html


Gondwana, with a large, developing glacier, nears southern Laurussia.

Fern-forests.

North America: The Antler arc collides with western North America creating the Antler orogeny.

Texas 320-360 Ma: shallow marine seas inland. Shales and limestones.




Rodinia blocks of Laurussia and Siberia collide to form Laurasia.

Reptiles.

North America: Gondwana collides from the south. The resulting Appalachian, Ouachita, Marathon, Ural, Variscan, and Hercynian orogenies formed some of the largest mountains of all time. The Ancestral Rockies form.

Texas 286-320 Ma: Ouachita Mountains. Collision formed inland basins filled by seas. Limestone, sandstone, shale.

Latest Paleozoic / Early Mesozoic

The supercontinent Pangaea dominates the Permian Earth, lying across the equator.

Extinctions! Trilobites go away.

North America: A new arc approaches western North America. A new spreading center forms as Cimmeria rifts from Gondwana and opens the Tethyian Ocean.

The western fringe of Pangaea lay along the eastern margin of the Pacific "ring of fire” subduction zone.

Texas 245-286 Ma: Shallow marine inland of mountains. Reefs. Evaporites. Red shales.http://vishnu.glg.nau.edu/rcb/globaltext.html

Latest Paleozoic / Early Mesozoic

Mammals.

North America: Arc collision along western edge forms the Sonoman orogeny.

As the Tethys Ocean expands, Cimmeria (Turkey, Iran, and Afghanistan) movenorthward towards Laurasia.

Texas 208-245 Ma: shales and sandstones in NW. Start opening the GOM - red sandstone, shale, evaporites.


Middle Mesozoic

Pangaea rotates; different components at different rates / in different directions -- rifts form.

Birds.

North America: Southern North Atlantic Ocean opens, continuing west into the Gulf of Mexico.

The Cordilleran arc develops along Pacific margin.

Arc forms on western side. Nevadan orogeny begins. Cimmeria begins collision with Laurasia - Cimmerian orogeny.

Texas 144-208 Ma: Change in sediment direction. Shallow water deposition / evaporites in GOM.http://vishnu.glg.nau.edu/rcb/globaltext.html

Middle Mesozoic

The Atlantic continues to expand as Pangaea breaks up.

The Cimmerian orogeny continues.

North America: Arcs and micro continents slam into western region. Laramide orogeny in Rockies.

Texas 66-144 Ma: Influx of sediment from Rockies. Shallow Cretaceous sea way across Texas. Shallow limestones, shales.


Late Cretaceous / Present

Rifts separate Africa and South America and then India, Australia, Antarctica. North America rifts from Europe.

Old Gondwana lands (Africa, India, Australia) move north toward Eurasia, closing the Tethys Ocean and forming the Alpine-Himalayan mountains.

The Atlantic lengthens / widens, the Sevier orogeny continues, and the Caribbean arc forms.

Texas 65-144 Ma: continuing shallow limestone and shale deposition to the southeast (from Rockies).


Paleocene / Eocene

Himalayan Orogeny. Alps and Pyrenees form.

The modern patterns of Planet Earth appear.

Atlantic continues to open. Rocky Mountains grow.

Texas 65 - 35 Ma: shale and sandstone in southeast region prograde shoreline (from the Rockies). Volcanic activity in Panhandle.


Oligocene and Miocene

Orogeny continues inthe Mediterranean region and India nears its junction with southern Asia.

Antarctica isolated.

Southwestern North America intercepts the East Pacific Rise and a great extensional event, the Basin and Range orogeny begins.

Texas 35-5 Ma: continued sandstone/shale deposition and progradation of shoreline (erosion of Rockies)


Present

Note: Best data set available.


Documents

Ch. 1 Dynamic and Evolving Earth ESCI 102 Spring 2005