Camping and woodcraft - Scoutmastercg.com

CAVE EXPLORATION 341to explore a cavern until he has learned how theseunderground passages are formed. To go ignorantlyinto such places is to lose most of their interestingfeatures and to court disaster.It is a common error to imagine that our cavernshave been caused by earthquakes or by volcanicforces. An earthquake may crack great cre\ icesin the crust of the earth, as at New Madrid, in181 1, and at Charleston, in 1886, but these arevery narrow in proportion to their length anddepth. It never forms vaulted chambers or smoothlyrounded passages.More numerous are the rifts and chasms left by"faults" in the rock where strata have been foldedin the slow shrinkage of mountain-building and thenhave been pulled apart by a subsidence. These, too,are only narrow fissures, and not caves at all.A volcano may form a sort of cave with its lavawhen the fluid mass underneath flows away andleaves an arch of its hardened crust in place. Suchaction is never found save in volcanic countries.Hot springs or geysers bore channels of escapefrom their deep reservoirs to the surface. Wherethe rock is soluble they may eat out large chambers,but they do not excavate lateral galleries.There is a class of horizontal caves in the facesof cliffs, very common in the Appalachians and inthe Southwest, that are called "rock houses." Thesealways are shallow enough to admit daylightthroughout their interiors, and they are dry. Theirorigin is evident. Where an exposed stratum ofvery soft rock underlies one of hard and imperviousmaterial, on the face of a cliff, the soft stone absorbswater, and when this freezes it -is cracked offand disintegrated. The debris is whirled aroundby the winds and helps to grind out a "room" underthe hard ledge that projects likea porch roof over>.head. Such places often are used for shelter bjman and beast. They are the "robber caves" and"bear dens" of song and storj^ but true cavernsthey are not.