Sipapu—The graceful arch of this bridge suggested to its namers the sipapu (place of emergence), a hole through which the Hopi believe their ancestors emerged from a lower, dark world into the present, sunlit one. This was also known as the Augusta Bridge.
The dimensions of the bridges are:
| Bridge | Height (feet) | Span (feet) | Width (feet) | Thickness (feet) |
| Owachomo | 106 | 180 | 27 | 9 |
| Kachina | 210 | 206 | 44 | 93 |
| Sipapu | 220 | 268 | 31 | 53 |
How Natural Bridges Are Made
To make a natural bridge Mother Nature must have several ingredients: a proper stone that will shape well (a cross-bedded sandstone is best), a slowly rising landscape, and a desert-type stream that occasionally will scour its bed with a tremendous head of water and sand. All these were present in southern Utah.
The stone of the Natural Bridges area is a cross-bedded grey sandstone, known as the Cedar Mesa sandstone. It is of Permian age and similar in appearance and structure to the more recent Navajo sandstone in which so many caves and arches have been formed.
When the land began to rise slowly from its ancient sea bed, two small streams formed on the western slopes of the Elk Ridge. The streams are known today as White River and Armstrong Creek, its tributary. They made meandering channels across the flat land and gradually entrenched themselves into tortuous canyons. As the land continued to rise, the streams cut ever deeper canyons.
The main purpose, or the driving force, of a stream is to make the shortest distance between two points, that is, a straight line. Every creek and river attempts to make a straight channel with an even grade from its source to its mouth. Hills, ridges, blocks of rock, or any other obstacles which a stream must bypass are gradually worn away as the stream makes a channel more to its choice.
The tortuous streams in their deep rock channels were constantly trying to straighten their courses. During floods the silt-laden waters were thrown with great force against the walls of the meanders. In several places the fins of rock around which the windings of the streams passed were so thin that during the course of many centuries of buffeting the rock gradually wore away and a hole was bored through the fin. The waters poured through the gap and the bridge was born. After the initial breach was made, the stream continued to enlarge the opening and to cut its channel still deeper. Eventually, the old meander was left high and dry as a “fossil” stream bed.