Home | Session 3 | Franciscan Formation Pg 1, 2, 3, 4

The Franciscan Formation: Where the Rock and Plate Tectonic Cycles Converge

Presented by Lisa White
San Francisco State University

Features of Plate Tectonic Margins

Click at left to zoom in on plate tectonic margins. What kinds of rocks form at:

Divergent boundaries (mid-ocean ridges and the ocean floor)?
Basalt and chert are common.

Convergent boundaries (trenches and subduction zones)? Graywacke and other turbidite sandstones and ultramafic rocks such as serpentinites are common.

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updated February 6, 2002

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