Plates of the Lithosphere. Pangaea – Giant supercontinent of the Paleozoic and Mesozoic eras Continental Drift – The breakup of Pangaea where plates moved.
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Plates of the Lithosphere
• Pangaea– Giant supercontinent of
the Paleozoic and Mesozoic eras
• Continental Drift– The breakup of Pangaea
where plates moved away from each other
Wegener’s Hypothesis
[Insert Fig. 30.1 - Pangaea]
• Fossils– Animal and plant
fossils appeared to have evolved in the same geographic region but now scattered on separate continents
Evidence of Continental Drift
Certain fossils appear in continuous bands across continents that are now separated across oceans. © Earth Observatory NASA
• Wegener could not produce a plausible mechanism as to how the continents drifted
Dismissal of Continental Drift
South America and Africa continents separated by the Atlantic Ocean appear to fit together like pieces of a puzzle. © Earth Observatory NASA
• Seafloor Spreading– New basaltic
rock forms along mid-ocean ridges and old seafloor is destroyed at deep ocean trenches
Emergence Plate Tectonics Theory
• Mid-ocean ridge– Linear mountains present in all ocean basics
• Age of ocean floor rocks– Young rocks near ridges and become progressively older
with increasing distance from the ridges
Evidence of Seafloor Spreading
• As a rift develops in a continental landmass, an ocean begins to open up
• As new seafloor is created along mid-ocean ridges, ocean floor diverges moving older seafloor away
Continental Drift Re-examined
• Lithospheric Plates– Large segments of lithosphere
• Plate Tectonics– The formation, movement and destruction of lithospheric plates
Plate Tectonics Theory
• Earthquakes, volcanoes and mountain ridges mark the location of plate boundaries
Location of Plate Boundaries
Cross section illustration of the three main types of plate boundaries: Divergent, convergent and transform plate boundaries © USGS
Movement of Plates
• Tensional forces result in plates moving apart
Divergent Plate Boundaries
• Compressional forces result in plates colliding with each other
• Depending on the types of crust that are colliding, convergent boundaries produce different land features
Convergent Plate Boundaries
Convergent Plate Boundaries
Convergent Plate Boundaries
• Shear forces result in two plates sliding past each other
Transform Boundaries
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