Descriptive Astronomy 101
Earth - Plate Tectonics


Plate Tectonics

1967 - Donald McKenzie and Robert Palmer propose the model of Plate Tectonics
Plate Tectonics is a combination of Continental Drift, Seafloor Spreading, Paleomagnetism, plus additional ideas.
Unifying Theory in Geology
The Theory:
There are 16 major tectonic plates, plus a number of minor or micro- plates.
Plates are composed of both oceanic and continental crust - often both are present within a single plate.
Plates are currently moving at rates of 2 to 15 cm per year.

Plate Boundaries

It is the interaction, between plates along the boundaries, that results in many of the geologic features we see today.
Three major types of plate boundaries:
1)
2)
3)

Divergent Boundaries

Plates are moving apart
Two main types of divergent boundaries
1)
2)

Convergent Boundaries

Plates are moving together
Three main types of convergent boundaries
1)
2)
3)
Style of convergence is controlled by the type of crust involved in the convergence.

Transform Boundaries

Plates are sliding past one another.
First described by J. Tuzo Wilson and Lynn Sykes
Similar to strike-slip faults but with an opposite sense of motion.

Transform Boundaries

Plates are sliding past one another.
The sense of offset is opposite the relative motion when occurring along mid-ocean ridges


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