For career geologists and casual enthusiasts of nature alike, it’s tough to beat Zion National Park. As Utah’s first national park, Zion is a popular travel destination throughout the year, where people can engage in a number of outdoor activities such as backpacking, canyoneering, camping, and other exciting ways to explore the wilderness.
For geoscientists, Zion National Park is more than just a beautiful slice of untamed nature: it is a veritable treasure trove of geological wonders waiting to be explored. For this reason, those with a background in geology find Zion to be an excellent place to conduct borehole logging and other types of geological measurement in order to better understand the mysteries of the Earth’s formation. Let’s take a look at some of the geology of Zion National Park.
Zion is located along the edge of a region called the Colorado Plateau. A geological feature known as the Grand Staircase is one of the main attractions for tourists. It consists of a series of colorful cliffs stretching between Bryce Canyon and the Grand Canyon and was formed by the uplift, tilting, and erosion of rock layers. The bottom layer of rock at Bryce Canyon is the top layer at Zion, and the bottom layer at Zion is the top layer at the Grand Canyon, thus forming the natural “staircase” of rocks.
This unusual formation is especially awe-inspiring If you consider that Zion was a relatively flat basin near sea level 275 million years ago. After erosion from surrounding mountains and streams carried sand, gravel, and mud into the basin, these heavy layers eventually caused the basin to sink. Because of this, the top surface has always remained near sea level.
The geological landscape of what is now Zion National Park has run the gamut from shallow seas to coastal plains to a massive desert over the millennia, due to climate change-induced rises and dips in the land. Over 10,000 feet of sediment accumulated during this process.
Over the millions of years of its existence, Zion’s elevation has risen from near sea level to as high as 10,000 feet above sea level. This is due to a process called uplift, which occurs in an area from Zion to the Rocky Mountains. Here, underground forces began pushing the surface up in huge vertical blocks. This process, called uplift, is still occurring to this day- in 1992 a magnitude 5.8 earthquake due to uplift caused a landslide visible just outside the south entrance of the park.
Uplift is also the cause of erosion in Zion National Park since it gave the streams increased cutting force as they made their way to the sea. Zion’s location on the western edge of this uplif caused the streams to fall off the plateau and flow rapidly down a steep incline. As this occurred, the streams began eroding, cutting into the layers of rock to form deep, narrow gulches. Over time, one of these streams, the Virgin River, has carried away several thousand feet of rock, a process that continues to occur to this day.
The Virgin River has created a geological feature known as a slot canyon by cutting through Navajo sandstone upstream from the Temple of Sinawava. At the Temple, the river has eroded the shale and collapsed the sandstone of the softer Kayenta Formation below, causing a widening of the canyon over time.
Another natural geological process on display at Zion National Park is lithification, which occurrs when mineral-rich water slowly filters through compressed layers of sediment. Minerals such as iron oxide, calcium carbonate, and silica bound to the deposits, transforming into stone due to pressure from overlying layers over long periods of time. What was once mud and clay has been transformed into mudstone and shale. What was formerly ancient seabeds is now limestone. Sand dunes and river sand have become sandstone. Because each layer originated from a distinct source, the mineral content, color, thickness, and eroded appearance of each layer is unique.
As if this wasn’t enough to pique a geoscientist’s interest, the park has also been shaped over the millennia by volcanic activity. Volcanic vents were created as a result of the weakening of the Earth’s crust during uplift, which allowed lava flows and cinder cones to form. This cinder was piled several hundred feet high in cone shapes, and the lava flowed into valleys. Cinder cones and black basalt flows can be seen on Kolob Terrace and west of Rockville.
Perhaps one of the most interesting things about Zion National Park that keeps geologists coming back for further study is the fact that it continues to change even today. For example, a landslide that once held back the Virgin River, forming a lake, became active again in 1995. This activity damaged the scenic road south of the Zion Lodge near the Sentinel Slide.
Additionally, visitors to present-day Zion face the potential for flash flooding that suddenly and without warning can exponentially increase the volume of the Virgin River. Flash floods occur when sudden thunderstorms dump water on exposed rock. With little soil to absorb the rain, runoff occurs quickly. In 1998, the scenic drive at the Sentinel Slide was damaged once more by a flash flood that increased the volume of the Virgin River from 200 cubic feet per second to 4,500 cubic feet per second. The flash floods, earthquakes, rockslides, and more that continue to occur at Zion National Park are a reminder that geology is not something that just happened in the past to form the Earth, but is an active and constant force that continues to change the landscape of our planet to this day.
With thousands of visitors per day, Zion National Park remains a celebrated destination for nature lovers wishing to see our Earth in its most natural form. There’s so much to explore and discover, both for experienced geologists and those who just appreciate beautiful natural vistas. If you’re planning a geological study trip to Zion National Park in the near future, be sure to bring your tools for borehole logging, measurement, and more, since this is about as good as it gets!
