Chapter 3 - Drifting Continents and Spreading Seas Flashcards
Continental Drift?
Wegener proposed, instead, that the continents once fit together like pieces of a giant jigsaw puzzle, to make one vast supercontinent. He suggested that this supercontinent, which he named Pangaea (pronounced pan-jee-ah; Greek for all land), later fragmented into separate continents that drifted apart, moving slowly to their present positions ( Fig. 3.1 ). This model came to be known as continental drift .
sea-floor spreading is?
The revolution began in 1960, when Harry Hess, of Princeton University, proposed that “as continents drift apart, new ocean floor forms between them” by a ‘process’ that his contemporary, Robert Dietz, also described and named sea-floor spreading .
World War II, it became clear that earthquakes do not occur randomly, but rather
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define distinct belts
World War II, it became clear that earthquakes do not occur randomly, but rather
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define distinct belts
where does movement of crust take place..
in bathymetric features
Research about the ocean floor in the mid-20th century provided clues that ultimately led to the proposal of
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sea-floor spreading
Studies of ocean floor bathymetry reveal the existence of
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abyssal plains, mid-ocean ridges, deep-sea trenches, and fracture zones.
Copyright | W. W. Norton & Company | Earth: Portrait of a Planet (Fourth Edition) | charmsofgold@gmail.com | Printed from www.chegg.com
Studies of ocean floor bathymetry reveal the existence of
Copyright | W. W. Norton & Company | Earth: Portrait of a Planet (Fourth Edition) | charmsofgold@gmail.com | Printed from www.chegg.com
abyssal plains, mid-ocean ridges, deep-sea trenches, and fracture zones.
Copyright | W. W. Norton & Company | Earth: Portrait of a Planet (Fourth Edition) | charmsofgold@gmail.com | Printed from www.chegg.com
Volcanoes occur in arcs bordering trenches and on islands at the end of
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seamount chains
Oceanic crust consists of
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basalt overlain by sediment
Oceanic crust consists of
Copyright | W. W. Norton & Company | Earth: Portrait of a Planet (Fourth Edition) | charmsofgold@gmail.com | Printed from www.chegg.com
basalt overlain by sediment
Heat flow increases toward the
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axis of mid-ocean ridge
Most earthquakes occur in
Copyright | W. W. Norton & Company | Earth: Portrait of a Planet (Fourth Edition) | charmsofgold@gmail.com | Printed from www.chegg.com
distinct belts
Hess proposed that ocean basins get wider with time by formation of new crust at mid-ocean ridges, a process called
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sea-floor spreading
Old ocean floor slides back into the mantle at
Copyright | W. W. Norton & Company | Earth: Portrait of a Planet (Fourth Edition) | charmsofgold@gmail.com | Printed from www.chegg.com
trenches
Two continents move apart when sea-floor spreading occurs between them.
T OR F?
T!
Magnetic Anomaly
the difference between the expected strength of the Earth’s main dipole field at a certain location and the actual measured strength of the magnetic field at that location.
Magnetic Anomaly
the difference between the expected strength of the Earth’s main dipole field at a certain location and the actual measured strength of the magnetic field at that location.
Magnetic Reversals
Times when the Earth’s field flips from normal to reversed polarity, or vice versa,
Magnetic Reversals
Times when the Earth’s field flips from normal to reversed polarity, or vice versa,
When geologists compiled data from many cruises on a map, these ______ defined distinctive, alternating bands.
marine magnetic anomalies
When geologists compiled data from many cruises on a map, these ______ defined distinctive, alternating bands.
marine magnetic anomalies
magnetic-reversal chronology
Geologists applied the technique to determine the ages of rock layers in which they obtained their paleomagnetic mea-surements, and thus determined when the magnetic field of the Earth reversed. With this information, they constructed a history of magnetic reversals for the past 4.5 million years.
magnetic-reversal chronology
Geologists applied the technique to determine the ages of rock layers in which they obtained their paleomagnetic mea-surements, and thus determined when the magnetic field of the Earth reversed. With this information, they constructed a history of magnetic reversals for the past 4.5 million years.
