Plate Tectonics

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Plate Tectonics

• Relatively new theory - introduced about 30 years
  ago
• Unifies several branches of the Earth Sciences
• http//pubs.usgs.gov/publications/text/dynamic.htm
  l

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In 1858, geographer Antonio Snider-Pellegrini
made these two maps showing his version of how
the American and African continents may once
have fit together, then later separated.
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Alfred Lothar Wegener

• Developed the Theory of Continental Drift
• Published Die Entstehung der Kontinente und
  Ozeane in 1915

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BUT -

• NO MECHANISM !!!

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Mid-Ocean Ridges
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Seafloor Spreading
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Paleomagnetism
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Magnetic Striping
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Continental Drift Seafloor Spreading A
few refinements PLATE TECTONICS
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All Plates are surrounded bya combination of
three differenttypes of boundaries

• Divergent
• Convergent
• Transform

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Divergent Boundary
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Mid-Ocean Ridges
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Continental Rift Systems
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Convergent Boundary

• Three Types
• Ocean-Ocean Collision
• Continent-Ocean Collision
• Continent-Continent Collision

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Ocean-Ocean Collision
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Ocean-Continent Collision
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Continent-Continent Collision
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Transform Boundry
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Satellite measurements of plate movement
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Formation and Differentiation of the Earth
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Hadean and Archean Eons
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Archean (until 2.5 BYA)

• Atmosphere composed of methane, ammonia, hydrogen
  and very little oxygen
• Very primitive life bacteria and stromatolites
  (3.4 3.5 billion years ago)
• - prokaryotes
• Cratons of significant
• size begin to form
• approximately
• 3 billion years ago

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Prokaryotes

• individuals (not colonial)
• single celled
• no nucleus
• no partitions
• Originally
• heterotrophic
• (ate others)

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• Autotrophs (organisms capable of creating their
  own food i.e. photosynthesis) appeared about 2
  bya.
• Originally referred to
• as blue-green algae they
• are actually closer to
• bacteria and are
• photosynthetic
• prokaryotes

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stromatolites
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• Proterozoic
• EON
• Moderate levels of
• oxygen in the atmosphere
• were reached about
• 2 billion years ago
• Oldest multicellular life
• 1.3 bya
• Stable continents form

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Eukaryotic Organisms

• evolved 1.7 bya
• have nucleus and internal chambers called
  organelles w/ specific functions
• unicellular, colonial or multicellular
• Introduction of Sexual Reproduction !
• Multicellular animal life evolved 670 Mya

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Pangaea I ??
Rodinia was a supercontinent formed about 1100
million years ago (that's 1,100,000,000 years)
situated about the South Pole. 750 million years
ago, Rodinia broke into three pieces that drifted
apart as a new ocean formed between the pieces.
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The landmasses would collide again 650 Ma to form
Pannotia which would remain a supercontinent
until the very end of the Precambrian when it
started to break apart.
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Carbonate Bank
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• Most famous examples of early animal life are the
  Ediacara Hills Fossils - actually impressions in
  sandstone with no hardparts
• 670 Mya
• All softbodied organisms
• segmented worms
• pre-arthropods
• jellyfish
• shell-less mollusks

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Ediacara Fossils
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Phanerozoic Eon - Palozoic Era

• Cambrian Period - 570 million years ago
• Explosion of life in the sea
• No life on land or in the deep sea
• Exoskeletons develop

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550 million years ago
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ArchaeocyathidsStromatolites
Reef Builders
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Tommotion Fauna - oldest diverse skeletonized
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Burgess Shale 530 Mya
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Wiwaxia
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Anomalocaris canadensis
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Pikaia gracilens first chordate ?
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Chordates

• Notochord - a stiff rod or chord
• Dorsal hollow nerve cord
• bilateral symmetry
• encephalization - complex central nervous and
  neural material structure brain

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Vertebrates

• characterized chiefly by a vertebral column
• Earliest known was the conodont
• Fish also evolved during the Cambrian

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Life
Trilobites
Conodonts
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Virtually all of the major landmasses lie on or
near the equator, warm temperatures, lots of
evaporation
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550 million years ago
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520 million years ago
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505 million years ago
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Cambrian Ended with a Mass Extinction505
million years agoOrdovician started
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Laurentia (still missing Europe) located on the
equator in tropical to sub-tropical zone -
widespread flooding of cratons
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Ordovician Life
Crinoids
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Brachiopods
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Predators
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Ordovician ends withanother mass
extinctionclimate gets much colder438 million
years agoSilurian Starts
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Silurian Life
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Rugose Corals and Bryozoansnew reef builders
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Eurypterids
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Gnathostomata

• true jaws

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Plants start to colonize the land
Plants use SPORES to reproduce Are confined to
very moist areas near sources of water
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Silurian Period

• Oceans high - most land flooded - partial glacial
  melting in Gondwanaland

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Silurian ends without a big mass extinctionand
408 million years agoDevonian Starts
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Devonian Life
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Armored fish appear
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Seed Plants Develop !
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Fish

• Chondrichthyes - cartilage fish (sharks)
• Osteichthyes - bone fish
• Actinopterygii - ray finned fish (look in a fish
  tank)
• Sarcopterygii - lobe-finned fish (lungfish,
  coelocanths and eventually tetrapods !

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• The oldest known skeletal remains of terrestrial
  vertebrates were found in the Upper/Late Devonian

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Devonian Ends with Laurentia attached to
Baltica360 million years agoCarboniferous
Starts
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• Tetrapods originated no later than the
  Mississippian (about 350 million years ago), the
  period from which the oldest known relatives of
  living amphibians are known.
• The oldest Amniotes currently known date from
  the Middle Pennsylvanian

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Tetrapods

• four feet
• modified vertebrae (processes etc)
• limbs all have single upper bone and lower paired
  bones
• the general body plan that we discussed last
  week

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Amniota

• The amniotic egg possesses a unique set of
  membranes amnion, chorion, and allantois. The
  amnion surrounds the embryo and creates a
  fluid-filled cavity in which the embryo develops.
  The chorion forms a protective membrane around
  the egg. The allantois is closely applied against
  the chorion, where it performs gas exchange and
  stores metabolic wastes (and becomes the urinary
  bladder in the adult). As in other vertebrates,
  nutrients for the developing embryo are stored in
  the yolk sac, which is much larger in amniotes
  than in vertebrates generally.

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Amniotic egg
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Carboniferous Life
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The move onto land !
Amphibians
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360 - 320 million years ago
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Land plants
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Coal Swamp
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320 Ma to 288 Ma
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Great Split

• Between 310 and 320 million years ago the
  Amniotes split into two groups characterized by
  skull morphology
• Synapsida
• Reptillia

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Anapsida
primitive condition - solid cheek bones
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Synapsida

• skull roof has developed a low opening (fenestra)
  behind the eye - the lower temporal fenestra

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Dimetrodon
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Permian 286 - 245 mya

• Pangaea fully formed - southeast Asia attached
  too
• World wide sea-level drop continues
• Global cooling
• Synapsids radiating over terrestrial plane
• (ancestors to mammals)

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288 Ma
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250 Ma
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Triassic 220 million years ago
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Triassic

• Synapsida dominant terrestrial vertebrate
• The other branch of the Amniotes is Reptilia
• Anapsid
• Diapsida
• Lepidosauromorpha (lizards and snakes)
• Archosauria (crocodiles, dinosaurs, pterosaurs,
  birds)

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Late Triassic

• All Continents still together in Pangaea
• No Polar Ice Caps
• Warm and generally stable climate
• Might have been highly monsoonal
• Dinosaurs first appear as do mammals, turtles,
  and pterosaurs
• Shallow warm seas
• Land plants seed ferns, conifers, ginkgoes
• Gymnosperms

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Late Triassic - Beginning of the Age of Dinosaurs
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Early/Middle Jurassic

• 208 - 157 Ma
• Dinosaurs became the largest, most successful
  terrestrial group
• Pangaea was breaking apart
• Huge deserts in parts of Pangaea
• still gymnosperms - seed ferns gone
• Large amphibians gone

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Early Jurassic
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Middle Jurassic
190 million years ago
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Late Jurassic

• Golden Age of Dinosaurs
• largest dinosaurs
• Laurasia and Gondwana totally separated by Tethys
  Sea
• warmer and wetter climate

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Early Cretaceous

• 145 - 100 Ma
• profound change
• world wide sea level rise
• flowering plants appear - angiosperms
• Gondwana breaks up
• temperate - low gradient

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136 million years ago
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Middle to Late Cretaceous

• 100 - 65 Ma
• Gondwana is split and Laurasia is breaking up
• sea-level at a high
• temperate - wall to wall Jamaica
• hot and wet greenhouse
• flowering plants dominate land
• very different dinosaurs

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65 million years ago
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Present