Hurricane Fault - Coal Creek Trail

Have you ever felt an earthquake? Earthquakes typically caused by the sudden release of energy from motion along a fault. Faults are defined as fractures in the Earth’s crust that have displacement or offset. At this stop, you are standing at the approximate location of the largest active fault in Southern Utah. Can you find any evidence of a large fault?

Hurricane Fault illustration over a photograph — The approximate location of the Hurricane Fault Line in Cedar City is shown by the dashed yellow line. This fault separates the mountainous region to the East from the relatively flat Cedar Valley.

How do faults form?

Faults are caused by outside forces acting on the rock. Most faults on Earth are the result of tectonic plates moving slowly to pull or push on different parts of the crust. As this happens the crust will break into separate blocks of rock that then shift in opposite directions along a fault. Depending on the direction of forces (pulling or pushing) different types of faults can form.

There are 3 basic types of faults.

Normal Fault illustration — Normal faults are the result of pulling forces (aka tension). This causes one side of the fault to essentially slide downward.The Hurricane Fault is an example of a normal fault.

Reverse Fault illustration — Reverse faults (sometimes called thrust faults for lower angle faults) are the result of pushing forces (aka compression). This causes one side of the fault to be pushed up the fault slope. These faults are common in large mountain belts like the Himalayas in Asia or the Andes in South America.

Strike-Slip fault illustration — Strike-slip faults occur when each side moves laterally in opposite directions. Notice that there isn't any vertical offset like the previous fault types. These faults are further classified by the direction of motion of the opposite blocks (hence right lateral above). The San Andreas Fault in California is an example of a strike-slip fault.

The Basin and Range

For the past 20 million years a portion of western North America, including western Utah, have been slowly stretching apart. This has caused many normal faults to form. These faults cause one side to drop down to form basins and the other side to uplift to form mountain ranges. Our region is dominated by these features, giving us the geographical region known as the basin and range. Cedar City is located on the eastern edge of this region, which is marked by the large-scale offset of the Hurricane Fault (see image at the top).

The fault is easily recognized by the flat and relatively low Cedar Valley on the west and the elevated Markagunt Plateau on the east. The eastern edge of Cedar Valley is marked by a rapid rise in topography. The fault is at the base of this rise. The Hurricane Fault extends about 250 km (~155 miles) from northern Arizona to just north of Cedar City.

Crustal extension illustration — This image shows a simplified cross section view of the region known as the Basin and Range. As the crust gets stretched apart it breaks into separate blocks that shift along normal faults. The result of this are parallel mountain ranges separated by low valleys or basins. The stretching can also trigger volcanic eruptions, which is responsible for the many dark volcanic rocks we see around Cedar City.

Uplift and Erosion

Cedar Canyon is a beautiful feature that hosts the Coal Creek paved trail. This canyon exhibits wonderful views and a variety of interesting rock features. The canyon itself was carved by Coal Creek. Rapidly flowing water, especially during flood events has slowly cut down into solid rock to produce the canyon. However, the canyon itself is also directly connected to the Hurricane Fault. As the Markagunt Plateau rises and Cedar Valley drops (relatively), the slope of Coal Creek steepens. This gives the creek more power to remove rock material as it flows. Without the Hurricane Fault causing uplift the creek would not be steep or fast enough to produce such a magnificent canyon. In fact, the Hurricane Fault is responsible for many canyons such as Kannarra Canyon or even Zion Canyon for the same reason.

Earthquakes

The Hurricane Fault is an active fault. It produces frequent earthquakes. The vast majority of these are very small, but based on the length and overall offset along the fault it is capable of large, energetic earthquakes. Even as large as a magnitude 7. Earthquakes happen when there is a sudden shift on a fault. As this happens energy is released in the form of seismic waves which can move Earth’s surface up and down or side to side. Since Cedar City is in earthquake country, it is very important to be prepared for large earthquakes.

Learn more about earthquakes

Educator Resources

Educators can download resources for teaching on the Coal Creek Trail.

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