Online Encyclopedia

Search over 40,000 articles from the original, classic Encyclopedia Britannica, 11th Edition.

LACCOLITE (Gr. XhKKOS, cistern, XLOos...

Online Encyclopedia

Originally appearing in Volume V16, Page 37 of the 1911 Encyclopedia Britannica.

» Make a correction to this article.
» Add information or comments to this article.

Encyclopedia Home :: KRO-LAP

Spread the word:

del.icio.us it!

See also:

LACCOLITE (Gr. XhKKOS, cistern, XLOos, stone)

LACCOLITE (Gr. XhKKOS, cistern, XLOos, See also:
STONE
STONE (0. Eng. shin; the word is common to Teutonic languages, cf. Ger. Stein, Du. steen, Dan. and Swed. sten; the root is also seen in Gr. aria, pebble)
STONE, CHARLES POMEROY (1824-1887)
STONE, EDWARD JAMES (1831-1897)
STONE, FRANK (1800-1859)
STONE, GEORGE (1708—1764)
STONE, LUCY [BLACKWELL] (1818-1893)
STONE, MARCUS (184o— )
STONE, NICHOLAS (1586-1647)
stone) , !in See also:

GEOLOGY (from Gr. yp7, the earth, and Abyor, science)

geology, the name given by See also:

Grove K. See also:

Gilbert to intrusive masses of igneous See also:

rock possessing a cake-like See also:

FORM (Lat. forma)

form, which he first described from the See also:

Henry Mountains of See also:

SOUTHERN

southern See also:

UTAH

Utah. Their characteristic is that they have spread out along the bedding planes of the strata, but are not so broad and thin as the sheets or intrusive sills which, consisting usually of basic rocks, have spread over immense distances without attaining any See also:

GREAT

great thickness. Laccolites See also:

COVER (from the Fr. convert, from couvrir, to cover, Lat. cooperire)

cover a comparatively small See also:

AREA

area and have greater thickness. Typically they have a domed upper See also:

SURFACE

surface while their See also:

BASE

base is See also:

FLAT (a modification of O. Eng. flet, an obsolete word of Teutonic origin, meaning the ground beneath the feet)

flat. In the Henry Mountains they are from I to 5 M. in See also:

DIAMETER (from the Cr. &a, through, µErpov, measure)

diameter and range in thickness up to about 5000 ft. The cause of their See also:

PECULIAR

peculiar shape appears to be the viscosity of the rock injected, which is usually of inter-mediate See also:

CHARACTER (Gr. xapareri7p, from xap&crew, to scratch)

character and comparatively See also:

rich in alkalis, belonging to the trachytes and similar lithological types. These are much less fluid than the basalts, and the latter in consequence spread out much more readily along the bedding planes, forming thin flat-topped sills. At each See also:

side the laccolites thin out rapidly so that their upper surface slopes steeply to the margins. The strata above them which have been uplifted and See also:

bent are often cracked by See also:

EXTENSION (Lat. ex, out ; tendere, to stretch)

extension, and as the igneous materials well into the fissures a large number of dikes is produced. At the base of the laccolite, on the other See also:

hand, the strata are flat and dikes are rare, though there may be a conduit up which the magma See also:

Las flowed into the laccolite.

The rocks around are often much affected by contact alteration, and great masses of them have sometimes sunk into the laccolite, where they may be partly melted and absorbed. Gilbert obtained See also:

EVIDENCE (Lat. evidentia, evideri, to appear clearly)

evidence that these laccolites were filled at depths of 7000 to Io,000 ft. and did not reach the surface, giving rise to volcanoes. From the effects on the drainage of the See also:

COUNTRY (from the Mid. Eng. contre or contrie, and O. Fr. cuntree; Late Lat. contrata, showing the derivation from contra, opposite, over against, thus the tract of land which fronts the sight, cf. Ger. Gegend, neighbourhood)

country it seemed probable that above the laccolites the strata swelled up in flattish eminences. Often they occur side by side in See also:

groups belonging to a single See also:

period, though all the members of each See also:

GROUP

group are not strictly of the same See also:

AGE (Fr. age, through late Lat. aetaticum, from aetas)

age. One laccolite may be formed on the side of an earlier one, and See also:

compound laccolites also occur. When exposed by erosion they give rise to hills, and their See also:

APPEARANCE (from Lat. apparere, to appear)

appearance varies somewhat with the See also:

STAGE (Fr. 6/age; from Lat. stare, to stand)

stage of development. In the western See also:

PART

part of See also:

South See also:

AMERICA

America laccolites agreeing in all essential points with those described by Gilbert occur inconsiderable See also:

numbers and See also:

PRESENT

present some diversity of types. Occasionally they areasymmetrical, or have one steep or See also:

VERTICAL (from Lat. vertex, highest point)

vertical side while the other is gently inclined. In other cases they split into a number of sheets spreading outwards through the rocks around. But the See also:

TERM

term laccolite has also been adopted by geologists in See also:

BRITAIN (Gr. Hperavuml vi7vot, Bperravia; Lat. Britannia, rarely Britannia)

Britain and elsewhere to describe a variety of intrusive masses not strictly identical in character with those of the Henry Mountains. Some of these See also:

REST (O. Eng. rest, reste, bed, cognate with other Teutonic forms, e.g. Ger. Rast, Riiste, rest, and probably Gothic Rasta, league, i.e. resting or stopping place)

rest on a curved See also:

FLOOR (from O. Eng. flor, a word common to many Teutonic languages, cf. Dutch vloer, and Ger. Flur, a field, in the feminine, and a floor, masculine)

floor, like the See also:

GABBRO

gabbro masses of the Cuillin Hills in See also:

SKYE

Skye; others are injected along a flattish See also:

PLANE

plane of unconformability where one See also:

SYSTEM

system of rocks rests on the upturned and eroded edges of an older See also:

SERIES (a Latin word from serere, to join)

series. An example of the latter class is furnished by the See also:

FELSITE

felsite See also:

mass of the See also:

Black See also:

Hill in the Pentlands, near See also:

EDINBURGH

Edinburgh, which has followed the See also:

LINE

line between the See also:

SILURIAN

Silurian and the Old Red See also:

SANDSTONE

Sandstone, forcing the rocks upwards without spreading out laterally to any great extent.

The term laccolite has also been applied to many See also:

GRANITE (adapted from the Ital. granite, grained; Lat. granum, grain)

granite intrusions, such as those of See also:

CORNWALL

Cornwall. We know from the evidence of See also:

MINING

mining shafts which have been sunk in the country near the edge of these granites that they slope downwards underground with an See also:

ANGLE (from the Lat. angulus, a corner, a diminutive, of which the primitive form, angus, does not occur in Latin; cognate are the Lat. angere, to compress into a bend or to strangle, and the Gr. ayKOS, a bend; both connected with the Aryan root ank-, to

angle of twenty to See also:

THIRTY

thirty degrees. They have been proved also to have been injected along certain See also:

wall-marked horizons; so that although the rocks of the country have been folded in a very complicated manner the granite can often be shown to adhere closely to certain members of the stratigraphical sequence for a considerable distance. Hence it is clear that their upper surfaces are See also:

CONVEX

convex and gently arched, and it is conjectured that the strata must extend belo,v them, though at a great See also:

DEPTH

depth, forming a floor. The definite See also:

PROOF (in M. Eng. preove, proeve, preve, &°c., from O. Fr . prueve, proeve, &c., mod. preuve, Late. Lat. proba, probate, to prove, to test the goodness of anything, probus, good)

proof of this has not been attained for no borings have penetrated the granites and reached sedimentary rocks beneath them. But often in I mountainous countries where there are deep valleys the bases of great granite laccolites are exposed to view in the hill sides. These granite sills have a considerable thickness in proportion to their length, raise the rocks above them and fill them with dikes, and behave generally like typical laccolites. In contradistinction to intrusions of this type with a well-defined floor we may See also:

PLACE (through Fr. from Lat. platea, street; Gr. IrAar6s, wide)

place the batholiths, bysmaliths, plutonic plugs and See also:

STOCKS

stocks, which have vertical margins and apparently descend to unknown depths. It has been conjectured that masses of this type eat their way upwards by dissolving the rock above them and absorbing it, or excavate a passage by breaking up the roof of the space they occupy while the fragments detached sink downwards and are lost in the ascending magma. (J. S.

End of Article: LACCOLITE (Gr. XhKKOS, cistern, XLOos, stone)

Additional information and Comments

There are no comments yet for this article.

» Add information or comments to this article.

Please link directly to this article:
Highlight the code below, right click, and select "copy." Then paste it into your website, email, or other HTML.

Site content, images, and layout Copyright © 2006 - Net Industries, worldwide.
Do not copy, download, transfer, or otherwise replicate the site content in whole or in part.

Links to articles and home page are always encouraged.

[back]
LACCADIVE ISLANDS

[next]
LACE (corresponding to Ital. merletto, trina; Genoe...