Ch. 1 Dynamic and Evolving Earth

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Ch. 1 Dynamic and Evolving Earth
ESCI 518 Fall 2004
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Earth is a Dynamic and Evolving Planet

• changes in its surface

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Historical Geology

• in historical geology we study
• changes in our planet
• how and why past events happened
• implication for todays global ecosystems
• 3 main ideas of historical geology
• plate tectonics
• evolution
• uniformitarianism

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Plate Tectonic Theory

• Lithosphere is broken into individual pieces
  called plates

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

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Theory of Organic Evolution

• provides a framework for understanding the
  history of life
• Darwins On the Origin of Species by Means of
  Natural Selection, published in 1859
• revolutionized biology

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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

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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

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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

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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 Earths biota through time
• the time scale was subsequently dated in years
• using radiometric dating techniques

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Geologic Column and the Relative Geologic Time
Scale
Absolute ages (the numbers) were added much
later.
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Geologic Time Scale
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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

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How Does the Study of Historical Geology Benefit
Us?

• survival of the human species depends on
  understanding how Earths 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

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Latest Precambrian / Early PaleozoicSupercontine
nt Rodinia, centered about the south pole, breaks
apart. North America (Laurentia), Baltica, and
Siberia moved North. Marine Invertebrates.Nort
h 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
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Latest Precambrian / Early Paleozoic
Supercontinent Rodinia continues to break
apart. Pieces move north. -Fish. -Glaciation. No
rth 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
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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.
http//vishnu.glg.nau.edu/rcb/globaltext.html
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Middle / Late Paleozoic 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
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Middle / Late Paleozoic 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.
http//vishnu.glg.nau.edu/rcb/globaltext.html
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Middle / Late Paleozoic 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.
http//vishnu.glg.nau.edu/rcb/globaltext.html
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Latest Paleozoic / Early Mesozoic The
supercontinent Pangeae 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
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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) move northward towards
Laurasia. Texas 208-245 Ma shales and
sandstones in NW. Start opening the GOM - red
sandstone, shale, evaporites.
http//vishnu.glg.nau.edu/rcb/globaltext.html
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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
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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 liestones, shales.
http//vishnu.glg.nau.edu/rcb/globaltext.html
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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).
http//vishnu.glg.nau.edu/rcb/globaltext.html
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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.
http//vishnu.glg.nau.edu/rcb/globaltext.html
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Oligocene and Miocene Orogeny continues in the
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)
http//vishnu.glg.nau.edu/rcb/globaltext.html
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Present Note Best data set available.
http//vishnu.glg.nau.edu/rcb/globaltext.html
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Fossils

• Fossils are the remains or traces of prehistoric
  organisms
• Any evidence of past life
• Most common in sedimentary rocks
• and in some accumulations of pyroclastic
  materials, especially ash
• They are extremely useful for determining
  relative ages of strata
• geologists also use them to ascertain
  environments of deposition
• Fossils provide some of the evidence for organic
  evolution
• many fossils are of organisms now extinct

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How do Fossils Form?

• Remains of organisms are called body fossils
• mostly durable skeletal elements such as bones,
  teeth and shells

• rarely we might find entire animals preserved by
  freezing or mummification

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Trace Fossils

• Indications of organic activity including tracks,
  trails, burrows, and nests are called trace
  fossils
• A coprolite is a type of trace fossil consisting
  of fossilized feces that may provide information
  about the size and diet of the animal that
  produced it

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Trace Fossils

• A land-dwelling beaver, Paleocastor, made this
  spiral burrow in Nebraska

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Trace Fossils

• Fossilized feces (coprolite) of a carnivorous
  mammal
• specimen measures about 5 cm long and contains
  small fragments of bones

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Body Fossil Formation

• The most favorable conditions for preservation of
  body fossils occurs when the organism
• possesses a durable skeleton of some kind
• and lives in an area where burial is likely
• Body fossils may be preserved as
• unaltered remains, meaning they retain their
  original composition and structure,by freezing,
  mummification, in amber, in tar
• altered remains, with some change in composition
  or structure by being permineralized,
  recrystallized, replaced, carbonized

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Unaltered Remains

• Insects in amber

• Preservation in tar

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Unaltered Remains

• 40,000-year-old frozen baby mammoth found in
  Siberia in 1971
• hair around the feet is still visible

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Altered Remains

• Petrified tree stump in Florissant Fossil Beds
  National Monument, Colorado

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Altered Remains

• Carbon film of a palm frond

Carbon film of an insect
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Fossil Record

• The fossil record is the record of ancient life
  preserved as fossils in rocks
• The fossil record is very incomplete because of
• bacterial decay
• physical processes
• scavenging
• metamorphism
• In spite of this, fossils are quite common