that might be oriented horizontally, vertically, or in between. Faults are of various
sizes and observed displacements can range from a few centimeters to hundreds of
kilometers. The landscape rearrangement might be minor and noticeable only by
close examination of a road cut or so major that a range of mountains is formed.
In some faults the motion is imperceptible, and in others, displacement of tens of
meters can happen virtually instantaneously, inearthquakes. Displacements sel-
dom occur at even rates over any amounts of time and, in many places, can be
thought of moving in “fits and starts.”
There are many varieties of faults, but they are generally classified into four
main types. The first is the strike-slip fault. This is the situation in which the fault
plane is nearly vertical and the main forces are those of horizontal shear so that the
sides of the fault slide past each other and there is little vertical displacement. The
largest of this type are the transform faults separating crustal plates. The San
Andreas Fault of California is a prime example and its lateral displacement has
shown to be over 300 km. A second fault type is a normal fault. Tensional forces
stretch and break the rock along a mainly vertical fault plane and one side of the
fault is upthrown compared to the other. Vertical movement along some very old
faults has been shown to be over 15 km but, of course, the topographic expression
of this displacement is much softened by erosional forces. The reverse fault is the
third type and results from compressional forces displacing the one side of the
fault up and somewhat over the other side. The fourth fault type is the overthrust
characterized by compressional forces along a low angle fault plane over long dis-
tances described above as resulting from folding.
Landscapes of faulting can be quite dramatic. In the European Alps and the
American West are complex mountain ranges caused by faulting. When tensional
forces pull apart the crust, large blocks of many square kilometers and surrounded
by normal faults can be thrust upward or downward considerable elevations. The
former situation makes horsts (fault mountains) and the latter grabens (fault val-
leys). The altitude difference between the bottom of Death Valley, California,
United States (graben), and the abutting Panamint Range (horst) is somewhat over
3 km. In larger form this also appears as the Rift Valley system in eastern Africa.Folk Culture
A folk culture is composed of a traditional, nonurbanized group, who adhere
strongly to an established pattern of life with few cultural intrusions or innovations
from outside. Frequently, rules and rituals are in place in folk cultures that prohibit
adoption of many aspects of modernization. Members of folk cultures are often124 Folk Culture