MOUNTAINS 313 
The accompanying diagrams (Figs. 187 and. 188), 
showing the actual cross-sections of mountain ranges, 
will illustrate better than words some of the complex 
foldings of moun- 
tains. 
Besides these types 
of mountains, there are 
some in which the centre 
of a fold is made of a 
hard mass of rock, which, 
even after consider- 
able denudation, stands Fic. 186, 
rp ke Hake ecpane Two ridges produced by denudation of anticlinal 
in the axis of the fold. ridge. 
Again, the central mass 
of a mountain may be a lava intrusion (p. 349); and sometimes 
this has raised the layers into a dome, so that the strata dip away 
Section through a part of the Appalachian Mountains, showing overthrust 
fault and unsymmetrical folds. 
Fic. 188. 
Section through a part of the Appalachians, showing faults and overturned folds. 
in all directions from the centre! Then the mountain fold may 
not produce a ridge, but rather, a more or less dome-shaped mass. 
These are numerous in some parts of Colorado and Utah, notably 
in the Henry Mountains of the latter state. 
1 Such a dip in all directions from the centre is known as the qua-qua- 
versal dip. 
