Contact, Geological

The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Contact, Geological

 

the contact surface of rocks that form contiguous sections of the earth’s crust. Geological contacts are classified as normal, or stratigraphic, when sedimentary or effusive rock is deposited on older rock; intrusive, if comparatively young intrusive rock has broken through older rock, causing various changes in it; and tectonic, when rocks of different content, origin, and age adjoin along the surface of a tectonic fault.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
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