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Plate Tectonics
Drift theory made sense of:
1) seafloor features
(trenches, midocean ridges)
2) peculiar ages of
seafloor rocks
(young compared to
continents; young
near ridges, oldest
near trenches)
3) odd heat flow
patterns (high near
ridges, low near
trenches)
Text pg. 74
Drift theory explained other odd sea-floor features
Text pg. 97
1) The Emperor Seamount chain and
Hawaiian Island chain arose because the
Pacific Plate is moving over a “hotspot”
currently centered under Hawaii.
2) Flat-topped, subsurface seamounts (tablemounts
or guyots) are old, eroded, sunken volcanoes.
Text pg. 76
Drift theory explained odd patterns in sea-floor ages
1) Ocean crust is much younger than continental crust
2) Youngest ocean crust is near mid-ocean ridges and the oldest near deep-ocean trenches.
Text pg. 78
Drift theory explained non-random distribution of earthquakes
1) earthquakes are concentrated along mid-ocean ridges and deep-ocean trenches
2) the deepest earthquake foci lie near deep-ocean trenches
Drift theory resolved odd polar wandering curves
Predicted polar wandering curves based on
geomagnetic data from European rocks
(blue) and North American rocks (red)
Predicted polar wandering curves based on
geomagnetic data from European rocks(blue)
and North American rocks (red)
assuming continents were fixed.
assuming continents moved.
Text pg. 71
Text pg. 104-106
Continental Drift over last 200 MY & Ocean Origins
Ocean basins are defined by the placement of continents, so the oceans are
different ages: Pacific >400 MYA, Atlantic ~180 MYA, Indian ~100 MYA. The
once extensive Tethyan sea (~350 MYA) is now nearly extinct!
Crustal plates continue to move today: Relevance to Canada
The NEPTUNE project
(joint Canada-US) plans to
deploy an undersea network
of monitors connected by
fiber-optic cable to the shore
for real-time (web-based)
monitoring seismic activity,
crustal motion, and deep-sea
biology.
What effects did continent motion have on earth’s biota?