Plate Tectonics - the history of the theory

Other Plate Tectonics Info:

Plate Tectonics Intro
Plate Tectonics Basics
Plate Tectonics History

More links to web sites that contain information about Plate Tectonics can be accessed through the Links Page of this web site. The figures shown here were taken and/or modified from the USGS Plate Tectonics web pages.

Plate Tectonics, Other Implications and Discoveries:

For a cool website that shows what the surface of the earth has looked like in the geologic past, as well as a lot of other plate tectonic information, click here.

For exactly what plate tectonics is and how it's defined, click here.

How Fast do the plates move? Plate Velocities

Average 5 cm/yr
Range 2-20 cm/yr
How do we know?

inferred from knowing the ages of different sections of oceanic crust, measuring their distances from mid-ocean ridges, and dividing the distance by the age.
(more recently) measured (and confirmed) directly using the Global Positioning System (GPS).

Why do the plates move, and what controls their speed?

Possible Driving Mechanisms for Plate Tectonics (click here to see what the USGS says)

How is the Theory of Plate Tectonics useful?
(or)
How can we test plate tectonics? Parts of Geology explained by Plate Tectonics:

Earthquakes and their distribution (click on figure to see USGS's Earthquake map)

Oceanic Sediment thicknesses and ages - note that thickness of sediments in figure below increases with distance from ridge crest, and as age of crust increases. (click on figure below to see actual picture of the Glomar Challenger)

Since the time of the early DSDP, additional drilling and siesmic surveys have established the depth of sediments over much of the earth:

(click on the above image to go to the full size image)

Igneous Rock distributions
Metamorphic Rock Distributions
Formation of Continental Margins
Island Chains

a. Island arcs over subduction zones

b. Hotspot chains (click on figure to see what the USGS says about Hotspots)

Structure of Ophiolites and Oceanic Crust
Distribution of depths in the Ocean
Heatflow in the oceans.

Other Plate Tectonics Info:
Plate Tectonics Intro
Plate Tectonics Basics
Plate Tectonics History