Twelve Plate Evidence
Name: Loretta G.
Date: August 2, 2004
What evidence is there proving Earth is broken into
plates and are there 12 plates?
According to the US Geological Survey, there are seven major continental
There are also several smaller plates and sub-plates, including:
-Juan de Fuca
So, there are seven to fourteen plates depending on whether the smaller
plates are defined as independent or as sub-plates of the major ones.
Although plate tectonic theory is supported by a variety of observations,
the concept of plate tectonics was not widely accepted until the 1960's.
The item that persuaded many geologists was the discovery of residual
magnetism in the sea floor along with the understanding of periodic
pole reversals through geologic time. An Internet search on the term
Tectonics" will yield a variety of excellent sites that have detailed
explanations of the plates and the observations that support the plate
The University of California, Berkeley's Museum of Palentology has an
explanation of the history of plate tectonic theory at:
There are 7 major and 13 minor plates. These plates are lithospheric
plates which consist of the crust and part of the upper mantle.
Many earthquakes, volcanoes and mountain ranges are the result of
lithospheric plate motion.
The Oceanic Ridge System, essentially an underwater mountain range,
provides evidence of the sea floor spreading or moving. As a result of
this motion, lithospheric plates move away from these spreading centers
and are either subducted (forced to sink) elsewhere or collide with other
plates causing mountains to form like the Himalayas.
Much more information can be found on this subject by searching for "plate
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Update: June 2012