Tilted Layers - Coal Creek Trail

There is a scientific principle in geology called the principle of original horizontality. This principle explains that sedimentary rock layers are initially formed or deposited in a horizontal or flat position. If sedimentary layers are found in a position that is not horizontal then we can guess or infer that something must have moved the layers into a different position. Are the rock layers in a flat position? What could have caused the layers to move into an inclined or tilted position?

Tilted Layers - Moenave Formation — The image above shows one of the sedimentary layers called the Moenave Formation tilted at an angle of about 55° from horizontal. This tilting occurred slowly millions of years ago as tectonic activity caused large mountains to form in this area.

Ancient Mountain Building

If you guessed that plate tectonics caused the layers to tilt then you are correct! Earth's outermost layer is composed of rigid and brittle material called the lithosphere. This layer has broken into distinct puzzles like pieces that can move and interact with each other. These are the tectonic plates. Over 100 million years ago there was an oceanic plate near the western coastline of paleo-North America that was slowly moving eastward. This plate pushed and compressed the continent causing the layers of rock to buckle and fold. This led to the formation of a tall and extensive mountain range. This mountain range formed slowly over the course of tens of millions of years and caused the sedimentary rocks in Cedar city to deform and tilt as part of an ancient anticline fold called the Kanarra Anticline. At this stop you are viewing the eastern half or limb of this anticline.

Schematic image of an anticline. An anticline forms when rock layers slope away from a hinge or crest. The layers in the Red Hill are tilted as part of the east limb of an anticline.

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