Extrusive Rocks


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 It might be outdated or ideologically biased.

Extrusive Rocks

 

(or effusive rocks), igneous rocks which, like modern lavas, poured out onto the surface of the earth through volcanic vents or cracks in the earth’s crust and solidified in the form of flows, sheets, and domes.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
In addition, it is found that extrusive rocks (e.g., basalt and dacite) have much higher [kappa] compared to plutonic rocks; hypabyssal and pyroclastic rocks have relatively lower [kappa] (Table 2).
The extrusive rocks of the Sambava-Vohemar area are products of volcanic activity related to the Marion Hotspot, which, it is believed, was very active in the Upper Cretaceous (Meert and Tamrat, 2006; Torsvik et al., 1998).
Gamma ray spectrometry has been useful in determining the anomalous potassium, uranium and thorium concentration interpreted as alteration halos and linear discontinuities, associated with intermediate intrusive / extrusive rocks (Dickson and Scott, 1997).
Resting unconformably on these units are volcanic rocks of the Elenita (Triassic-Jurassic) and Henrietta (Jurassic) Formations, both intruded by plutons of Jurassic age--the extrusive rocks are the remnants of a volcanic arc which once extended from California into the Mexican state of Durango.