intrusion

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intrusion

1. Geology
a. the movement of magma from within the earth's crust into spaces in the overlying strata to form igneous rock
b. any igneous rock formed in this way
2. Property law an unlawful entry onto land by a stranger after determination of a particular estate of freehold and before the remainderman or reversioner has made entry
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Intrusion

 

a geological term used in two senses:

(1) The process of magma injection into the body of rock that forms the earth’s crust. The solidification of such injected magma leads to the formation of intrusive rock.

(2) An intrusion is a geological body composed of igneous rock and formed in the process of injection and solidification of mag-matic melt in the earth’s crust (intrusion, intrusive body, plutonic intrusion). In relation to the structure of the country rock, intrusions are classified as concordant and discordant. The first group includes sills, laccoliths, and lopoliths, and the second group includes batholiths, stocks, and dikes. Intrusions are classified according to the depths at which the magmatic intrusion occurred as deep-seated intrusions (abyssal) and shallow-depth intrusions (hypabyssal). In this context the conditions of cooling of the magma and its effect on surrounding rock differ sharply. At shallow depths the cooling is rapid and fine crystalline or porphyritic rock is formed, and contact metamorphosis affects a small area of the country rock. At great depths medium-grain and large-grain rock and major changes in the surrounding rock are characteristic.

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

intrusion

[in′trü·zhən]
(geology)
The process of emplacement of magma in preexisting rock. Also known as injection; invasion; irruption.
A large-scale sedimentary injection. Also known as sedimentary intrusion.
Any rock mass formed by an intrusive process.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

intrusion

Unauthorized access to a computer system or network. See intruder and IDS.
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