Plate Tectonics

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Plate Tectonics
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Plate tectonics

• A theory that states that the earths crust is
  made up of a number of plates which move over a
  liquid crust that get created and destroyed over
  time.

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Moving Plates

• The force for these movements is derived from
  magmatic convection cells in the asthenosphere of
  the mantle.
• The upward portion of these cells are known as
  magmatic plumes.
• When they hit the crust, the plate above is
  melted and forced to spread creating a spreading
  ridge as they are adding new continental material
  (constructive margin) to the edges of these
  plates.

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Evidence supporting plate tectonics

• Ages of oceanic crusts get older as one moves
  away from a spreading ridge.
• Ages of oceanic sediments on top of the crust
  gets older as one moves away from a spreading
  ridge.
• Rock formations with the same mineral content and
  age existing on opposite continental shores. The
  eastern most tip of south America and the African
  Congo both have the same iron ore rock formation.
  Rock formations are also shared between
  Newfoundland, Canada and the west coast of
  Ireland and southern India and South Africa.

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Evidence supporting plate tectonics

• Stationary hot-spots "burn" trails into moving
  continents.
• Magnetic anomalies showing variations in the
  Earths magnetic field strength are arranged in
  bands parallel to each other on either side of
  the spreading ridges.

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Evidence supporting plate tectonics

• Magnetic polarity reversals patterns are
  preserved as the rock formed, show symmetry about
  spreading ridges.
• The margins or edges of some continents have
  shapes that indicate that they once fit together.
  (i.e. South America fitting into Africa.)

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Evolution and Biodiversity Influenced by Plate
Activity
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Pangea

• Two hundred million years ago (Ma), research
  suggests that all the continents where one large
  mass which was named Pangea.
• Terrestrial organisms were able to migrate across
  all the continents and were only limited by their
  biotic potential.

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Biodiversity

• As Pangea began to separate into separate
  continents 130 Ma, creating physical barriers
  such as seas, restricting migration to within the
  continents.
• Gene pools of species are separated and as they
  are exposed to different physical (i.e. climate)
  and biotic (i.e. change in predators) conditions,
  each portion of the species adapts differently
  and eventually forms new species on the separated
  continents.
• This process is known as speciation.

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Biodiversity

• Changes in physical and biotic conditions will
  also lead to the creation of new species
  increasing the diversity of habitats and niches.
• This also provides the space for new species to
  evolve into these habitats.
• The end result of the separation of Pangea into
  todays continental configuration is that plate
  tectonics has been one of the main driving forces
  promoting biodiversity or organisms.

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Biodiversity

• In addition to continents separating, some like
  India left south Africa and Antarctica and joined
  up with Asia.
• It took with it organisms that were typical to
  Antarctica and Australia.
• Over the next 100 Myrs these organisms evolved in
  isolation from any other continent until it
  formed a land bridge with Asia.
• Since 30 Myrs ago the species on India and Asia
  have been re-adapting themselves causing
  additional biodiversity.

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Biodiversity

• Australia has one of the most unique sets of
  organisms as it and Antarctica have been separate
  from all the other continents for the last 130
  Myrs.
• Australia separated from Antarctica about 50 Myrs
  ago.
• This extreme isolation over such a long period of
  time supports Darwins theory of evolution in
  that this part of the world has the most unique
  organisms.
• Australian species have had such limited contact
  with species from other continents that they have
  only needed to adapt to their particular set of
  species and climate.
• No re-adaptation to other species from other
  continents has occurred until the arrival of the
  Europeans.

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Biodiversity

• The splitting up of Pangea 200 million years ago
  had the following effects on species diversity
  and distribution. a) Species gene pools or
  populations where split as Pangea separated. b)
  New habitats were created due to a change in
  biotic and abiotic factors such as climate
  (temperature and moisture), changes in species
  relationships, and topography.

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Biodiversity

• c) New niches were made available and filled
  causing further adaptation of species to new
  conditions thus modifying the local ecosystem.
• d) Species relationships change with respect to
  mutualism, predation, and competition. Species
  need to modify food source, protection, and
  dependence patterns in the food web.
• e) Speciation is the creation of a new species
  when a gene pool of one species is split, exposed
  to new conditions to which each pool adjusts to.
  Different genetic traits are passed on to
  offspring. A new species evolves once the 2
  original populations cannot mate.

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Biodiversity

• Rejoining of plates such as India and Asia. 30 Ma
  ago caused the following. a) Migration of one
  species into the territory of another introduces
  new forms of competition and predation that
  existing species need to adapt. b) Further
  speciation is generated and modified as they come
  into contact with a variation of the original
  gene pool.

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Biodiversity

• Extreme isolation such as Australia and
  Antarctica. 130 Ma of isolation. a) As no new
  predators are introduced over a long period of
  time speciation is limited to changes in abiotic
  factors such as climate and topography. b)
  Evolution tends to slow down and become more
  specialized if there are fewer stresses and
  ecosystem changes. c) Species evolve separately
  from original gene pool and tend to be very
  different from other areas with more contact with
  the original gene pool.