Principle of original horizontality

From these observations is derived the conclusion that the Earth has not been static and that great forces have been at work over long periods of time, further leading to the conclusions of the science of plate tectonics; that movement and collisions of large plates of the Earth's crust is the cause of folded strata.

[2] As one of Steno's Laws, the principle of original horizontality served well in the nascent days of geological science.

For instance, coarser grained sediments such as sand may be deposited at angles of up to 15 degrees, held up by the internal friction between grains which prevents them slumping to a lower angle without additional reworking or effort.

Also, sedimentary beds may pinch out along strike, implying that slight angles existed during their deposition.

Thus the principle of original horizontality is widely, but not universally, applicable in the study of sedimentology, stratigraphy, and structural geology.

The Permian through Jurassic stratigraphy of the Colorado Plateau area of southeastern Utah is a great example of Original Horizontality. These strata make up much of the famous prominent rock formations in widely spaced protected areas such as Capitol Reef National Park and Canyonlands National Park . From top to bottom: Rounded tan domes of the Navajo Sandstone , layered red Kayenta Formation , cliff-forming, vertically jointed, red Wingate Sandstone , slope-forming, purplish Chinle Formation , layered, lighter-red Moenkopi Formation , and white, layered Cutler Formation sandstone. Picture from Glen Canyon National Recreation Area , Utah.
A stratigraphic section of Ordovician rock exposed in central Tennessee , US. The sediments composing these rocks were formed in an ocean and deposited in horizontal layers.