Plate Tectonics

Drift theory made sense of:

Text pg. 74

1) seafloor features (trenches, mid-ocean 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)

Drift theory explained other odd sea-floor features

1) The Emperor Seamount chain and Hawaiian Island chain arose because the Pacific Plate is moving over a “hotspot” currently centered under Hawaii.

Text pg. 97

2) Flat-topped, subsurface seamounts (tablemounts or guyots) are old, eroded, sunken volcanoes.

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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.

Drift theory explained non-random distribution of earthquakesT

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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)

assuming continents were fixed.

Predicted polar wandering curves based on geomagnetic data from European rocks(blue) and North American rocks (red)

assuming continents moved.

Text pg. 71

Continental Drift over last 200 MY & Ocean OriginsT

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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?