LACCOLITHIC MOUNTAINS 
25 
BUSTER HYPOTHESIS OF LACCOLITHIC 
MOUNTAINS 
By Charle:s K^yes 
Introductory 
Touching casually upon the question of orgin of those anomal¬ 
ous intrusive bodies which we are pleased to designate laccoliths 
the late James D. Dana once remarked that there were “Various 
opinions but no positive knowledge.” In the generation which 
has passed since this trite statement was made there is much that 
is new which has been deciphered concerning the conditions under¬ 
lying this special form of magmatic activity. Between the two ex¬ 
treme views that have been presented, between the idea of an 
easily floated prism of strata which develops into a symmetrical, 
dome-shaped mountain, and the notion that a laccolith is a 
mechanical impossibility, there is a middle ground which although 
rendering improbable the one and perfectly invalidating the other 
is amply supported by wide observation and withal has the further 
advantage of being mathematically sound. The genetic control 
thus turns out to be dominantly erogenic rather than simply 
hydrostatic in nature. The most conspicuous feature involved 
thus becomes quite secondary instead of distinctly primary in 
character.^ 
Until G. K. Gilbert formally christened (1877) this distinctive 
type of mountain laccolithic structure had attracted small practi¬ 
cal attention. Nevertheless long before the Henry Mountains of 
Utah were graphically portrayed laccolithic forms were clearly 
figured out. Under other titles the identic tectonic forms were 
early known. Although not particularly distinguished from 
ordinary bosses certain special phases of the latter were 
differentiated. Fifty years prior to the appearance of the mem- 
1 Characteristics of Volcanoes, p. 24, New York, 1890. 
