Several phases of bridge-making may be seen at Natural Bridges National
Monument.
Kachina Bridge is a new bridge. It is huge and bulky, and has a
comparatively small opening. White River is still actively enlarging the
opening beneath the span.
Sipapu Bridge is mature. It is a graceful, symmetrical span, and its
abutments now lie far enough from the stream bed that the river has
little or no cutting action on the rock.
[Illustration: _Sipapu Bridge, looking up White Canyon._]
Owachomo Bridge is in its old age. It suffers no erosion from the
stream; only the slight erosion from rains, frost action, or wind-blown
sands now attack its surface. The life expectancy of Owachomo is short
compared with that of the other two; it may span the canyon for
centuries yet, or the crack which will ultimately cause its collapse may
already have started.
The fate of all the bridges may be seen a short distance up White Canyon
from Sipapu Bridge where faint scars and damaged abutments on the canyon
walls indicate the point where a fourth bridge once spanned the canyon.