Conversations with the Earth Tom Burbine [e-mail]

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Conversations with the EarthTom
Burbinetburbine_at_framingham.edu
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Quiz

• Monday for M,W, Th class
• Tuesday for T, Th class
• Covers material after last quiz
• Chemistry
• Global warming
• Dinosaur extinction

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Geologic time scale

• System of measurement relating stratigraphy to
  time that is used to describe the timing and
  relationships between events that have occurred
  during the history of the Earth.

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Stratigraphy

• Stratigraphy study of rock layers and layering

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Original Horizontality

• Layers of sediment are originally deposited as an
  even, horizontal layer
• Layers inclined at angles were moved by
  disturbances after deposition

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Superposition

• Each layer was deposited on top of older
  preexisting layers below

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Principle of Superposition

http//earthsci.org/fossils/geotime/time/Super.gif
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Exercise 3

• Question 1
• What is used to differentiate between different
  time periods?

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• Question 2
• How long ago did the dinosaurs become extinct?

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• Question 3
• How long were there dinosaurs living on the Earth?

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• Index fossils are fossils used to define and
  identify geologic periods
• The shorter the lifespan of a species, the more
  precisely different sediments can be correlated

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K-T layer

• K-T layer is the boundary between the Cretaceous
  (K) and Tertiary (T) time periods
• Clay layer that is found all
  over the globe

Colorado
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Wyoming
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Italy
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K-T Boundary

• 65 million years ago
• Boundary in the rock record separating the
  Cretaceous and Tertiary Periods
• Corresponds to one of the greatest mass
  extinctions in history
• 1 cm global layer of clay separating the two
  periods
• A reason for the extinction was proposed by
  Walter Alvarez and Luis Alvarez in 1980

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• Question 4
• Why is a high concentration of iridium evidence
  that an asteroid hit the Earth?

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Iridium

• Iridium (Ir) is a chemical element with atomic
  number 77
• Iridium is one of the least abundant elements
  (0.001 ppm) in the Earth's crust
• Iridium is much more abundant in meteorites (0.5
  ppm or higher)

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What happened?

• An asteroid roughly 10 km (6 miles) across hit
  Earth about 65 million years ago.
• This impact made a huge explosion and a crater
  about 180 km (roughly 110 miles) across.
• Debris from the explosion was thrown into the
  atmosphere, severely altering the climate, and
  leading to the extinction of roughly 60 of
  species that existed at that time, including the
  dinosaurs.

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Environmental Damage

• http//www4.tpgi.com.au/users/horsts/climate.htm

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• The worst hit organisms were those in the oceans.
• On land, the Dinosauria of course went extinct,
  along with the Pterosauria.
• Mammals and most non- dinosaurian reptiles seemed
  to be relatively unaffected.
• The terrestrial plants suffered to a large
  extent, except for the ferns, which show an
  apparently dramatic increase in diversity at the
  K-T boundary, a phenomenon known as the fern
  spike.

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• Pterosaurs were flying reptiles

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• Dinosaurs lived during the Mesozoic Era, from
  late in the Triassic period (about 225 million
  years ago) until the end of the Cretaceous (about
  65 million years ago).

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• Question 5
• What species today are direct descendants of the
  dinosaurs?

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Archaeopteryx

• Modern birds are considered
  to be the direct descendants
  of dinosaurs
• Idea first formulated in 1860s-1870s

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Rahonavis
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• http//www.hulu.com/watch/63729/nova-the-four-wing
  ed-dinosaur

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Any Questions?