monday november 1, 2010
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Monday November 1, 2010. (Continental Drift and Plate Tectonics). The Launch Pad Monday, 11/1/10. Why do modern birds show more of a similarity to modern reptiles than modern mammals show to modern reptiles?. - PowerPoint PPT PresentationTRANSCRIPT
MondayNovember 1, 2010
(Continental Drift and Plate Tectonics)
The Launch PadMonday, 11/1/10
Why do modern birds show more of a similarity to
modern reptiles than
modern mammals show to modern reptiles?Birds branched off from reptiles much later
than mammals did, thus retaining more of a similarity.
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Continental DriftAn Idea Before Its Time
German scientist Alfred Wegener first proposed the continental drift
hypothesis in 1915. His work was published as “The
Origin of Continents and Oceans.” The continental drift hypothesis
states that a supercontinent called Pangaea began breaking apart about
200 million years ago. The continents “drifted” to their
present positions. Continents “broke” through the
ocean crust.
Antonio Snider-Pellegrini (1858)
Alfred Wegener’s Pangaea
Pangaea approximately 200 million years ago
Figure 7.2
Continental Drift
Evidence Cited by Wegener
• Fit of South America and Africa
Continental Drift
Evidence Cited by Wegener • Fossils match across the
seas
Continental Drift
Evidence Cited by Wegener • Fossils match across the seas
Continental Drift
Evidence Cited by Wegener • Fossils match across the seas
Continental Drift
Evidence Cited by Wegener • Rock types and structures
Similar mountain ranges on different continents
Figure 7.7
Continental Drift
Evidence Cited by Wegener • Ancient climates –
climates evidence matches on present-day continents.
Figure 7.A The Breakup
of Pangaea
Continental DriftAn Idea Before Its Time
The main objection to Wegener’s proposal was the inability to
find a mechanism for continental drift.
The Continental Drift Mechanism Discovered: Plate TectonicsThe concept of plate tectonics is
more encompassing than the idea of continental drift.
Plate tectonics is associated with Earth’s rigid outer shell, called the
lithosphere. Earth’s lithosphere consists of
several “plates”, which are moving very slowly across the mobile
asthenosphere below.The largest of these plates is the
Pacific plate. The plates are mostly beneath the
ocean.
The Earth’s asthenosphere lies just beneath the
lithosphere. The asthenosphere is
hotter and weaker than the lithosphere.
This allows for the motion of the lithosphere over
the asthenosphere
Plate Tectonics
All major interactions among plates occur along their boundaries.
Plate Tectonics
Figure 12.6
GEODe Earth Science
Plate TectonicsSlides 698-725