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How ocean crust is made.

How ocean crust is made.
How ocean crust is made.
How ocean crust is made.
How ocean crust is made.
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596786
Doucette, Jayne H.
How ocean crust is made.
Illustration
01/01/2003
Kelemen_scenarios.jpg
Date is approximate.
Caption from Oceanus magazine, Vol. 42, No. 2, Pg. 43:
The crust beneath oceans and continents is fundamentally different. Continental crust is made of light-colored rocks called andesite and granite. Ocean crust is composed of dark-colored rocks called basalt and gabbro. Ocean crust originates as a “melt” that forms in submicroscopic pores in rocks in Earth’s hot mantle and rises to the surface. Scientists have pieced together clues to discover: 1) how melt that forms over hundreds of kilometers in the mantle is focused into a five-kilometer volcanic zone beneath mid-ocean ridges, and 2) how oceanic crust is formed with a relatively uniform, three-tiered structure consisting of gabbro, sheeted dikes, and lava flows.
Illustration by Jayne Doucette
© Woods Hole Oceanographic Institution
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