I’m going to change pace and do a short travel series: an in-depth look at Zion National Park. I’ve not done one of these for a long time. As usual I’ll start with Zion’s natural history, including geology in this post. Then I’ll go on to human history and life on display at Zion. I’ll finish with travel logistics and recommendations for various visit lengths, focusing of course on photography.
If you haven’t yet visited Zion, this series will be an in-depth introduction with tips, but without presuming to tell you exactly where and how to photograph the park. If you’ve been to Zion before, you will learn some interesting stuff about the park and probably find out about one or two out-of-the-way photo spots.
But mostly this is about background knowledge. I strongly believe the more you know about a place the better your experience and photos will be. Though my posts are always heavily illustrated, I hope you’ll try to forget the pictures when you go out yourself. Do your own thing and get pictures that represent your own unique take on the park.
Zion National Park lies in southwestern Utah, in an area called Dixie. That term is normally associated with the southern states (Alabama, Georgia, etc.). Utah’s Dixie is certainly where the climate is warmest in the Beehive State. But it’s much drier than the humid South. Zion is at the southwestern edge of the Colorado Plateau, that huge regional uplift of sedimentary rocks that covers parts of four states and defines much of the dramatic scenery of America’s desert southwest.
THE GRAND STAIRCASE
Zion is also on the western edge of a geologic feature called Grand Staircase. This is a large series of cliff-forming sedimentary layers that steps downward from north to south. Some of the area’s highest and youngest rocks are to the north near Bryce Canyon while some of the lowest and oldest rocks are exposed to the south in Grand Canyon.
But the rim of that last southern step (it’s a doozie!) tops out at 8800 feet in elevation on the north rim of the Grand Canyon. That’s very similar to the top of Bryce (the northern step) at 9100 feet. So the Grand Staircase not so much steps downward in elevation but in geology.
BREAKS & CANYONS
Zion Canyon, centerpiece of the park, plus Cedar Breaks to the north, are located where the land “breaks” downward off the high eastern plateaus of south-central Utah to meet the lower deserts of SW Utah and southern Nevada. These breaks are also known as the Hurricane Cliffs, which continue south into NW Arizona.
The towns in this part of Utah, largest of which is St. George, are situated near the foot of this dramatic sandstone escarpment, at a relatively low elevation compared with much smaller burgs up in the plateau country to the east. The Virgin River and its tributaries have cut generally SW-facing canyons down through the escarpment. The most dramatic of these is Zion Canyon.
THE GREAT JURASSIC DESERT
The most prominent formation at Zion is Navajo Sandstone. It forms most of the named dome-like features at Zion, such as the Patriarchs, the Sentinel, and White Throne. The Navajo, which is generally a whitish sandstone, preserves record of an ancient desert. This desert, which existed in the Jurassic age (dinosaur times), was dominated by enormous sand dune fields (ergs) similar to today’s Sahara Desert.
You can tell the rocks are ancient sand dunes because of cross-bedding. Take a good look at the sandstone walls at Zion and notice the lines angled at about 35 degrees to the main rock layers, which are nearly horizontal. A great place to see cross-bedding is at Checkerboard Mesa near the park’s east entrance, but you’ll see it everywhere in East Zion east of the tunnels. The rocks behind the sheep below show cross-bedding.
The desert sands of the Navajo formed when plate tectonics, beginning a couple hundred million years ago, dragged this area north from equatorial to much drier latitudes in the vicinity of the Tropic of Cancer (30 degrees north). This is the latitude, both north and south of the equator (Tropic of Capricorn), where the world’s major deserts are still found.
Also contributing to desertification in the Jurassic were the mountains building to the west of Zion in Nevada and California. These ranges, which were the result of tectonic collision at the western edge of North America, are now gone, eroded away. But in the Jurassic they formed an effective rain-shadow, blocking rains coming off the Pacific and helping to dry things even further.
There is more than Navajo Sandstone at Zion, however. The Virgin River has cut so deeply into the rocks that, despite the great thickness of the Navajo, other formations are visible beneath it. These record shallow seas, meandering streams and floodplain environments. For example, the Kayenta and Moenave Formations below the Navajo are reddish stream deposits formed in climates that changed from subtropical (for the older Moenave) to semi-arid (for the overlying Kayenta).
These older formations form the rubbly slopes and red cliff bands low on Zion’s canyon walls. They’re also prominent above the town of Springdale, and up on Kolob Terrace Road. Solid red cliffs of Kayenta, formed at the edge of that great encroaching desert, lie directly beneath the hard white sandstones of the Navajo.
If you gain a high vantage point you may notice the red “hats” or caps on top of the Navajo Formation’s highest white domes. These belong to the Temple Cap and Carmel Formations, at 160 million years the youngest rocks at Zion. Their reddish color is clue to wetter conditions returning in the late Jurassic. A warm sea even invaded again, this signaled by limestones of the Carmel Formation.
UPLIFT & EROSION
Time didn’t stop after deposition of the Navajo and other Jurassic rocks at Zion. Sedimentation continued into the Cretaceous and beyond; yet, save for an important exception (see below), younger rocks of the Zion region have been stripped away by erosion and transported down the Colorado River into the Pacific Ocean.
Erosion is a big deal at Zion. The Colorado Plateau continues to be shoved upward by tectonic pressures (a 5.8 magnitude earthquake shook Zion in 1995). Over time, this uplift has increased river gradients dramatically, resulting in very active erosion by streams and rivers as well as landslides. Wind has helped sculpt the landscape.
YOUNG LAVA FLOWS
If you drive up to Lava Point on the Kolob Terrace Road, you will notice dark lava flows, which flowed out of vents that opened up as this area began to stretch (rift), starting about 2 million years ago. This young age places the lava flows (which being basalt were quite fluid) in the Ice Ages, which were fairly wet times at Zion. Think about the terrain at that time, which was dramatic canyon country as it is today.
This combination of climate, active basaltic volcanism and topography tells you something must have happened (and it did!): lava-dammed lakes. If you hike the Subway, a lake formed in that canyon when lava dammed the Left Fork; it extended all the way up to the Subway itself. If you’re observant you’ll notice fine lake muds and silts laid down by this lake. You pass right by them when you’re hiking back out of the canyon.
By the way, let’s put some numbers on this story. Most of what you see at Zion is between about 200 and 160 million years old, placing it squarely in the Mesozoic Era, age of dinosaurs. Less noticeable rocks beneath these are as old as 250 million years, while the young lavas are between 1.5 and 200,000 years old.
TROPICAL SEAS AT ZION?
The older pre-dinosaur strata is worth mentioning because it is prominent at nearby attractions, such as Grand Canyon to the south of Zion. Most prominent of the area’s oldest rock formations is the Kaibab. It dates back to Permian times about 260 million years ago. In these ancient times, an embayment of the ocean we call Panthalassa lapped at the edge of the world’s only landmass, the supercontinent Pangaea. At that time this region, later to become Utah and Arizona, was near the equator.
The Kaibab is mostly limestone, formed in warm, shallow seas. It’s visible in places low along the Virgin River within the park and also dramatically in the Hurricane Cliffs near the town of Hurricane and north along the east side of I-15. It’s interesting to realize that the Kaibab, which hides low in Zion’s deep canyons, forms the high rim of Grand Canyon to the south. This tells you something about the layout of the Grand Staircase.
THE SENTINEL SLIDE
More recently during the Ice Ages, the climate at Zion was wetter than today’s. The Virgin and other rivers carried more water, thus flash-flooding was more frequent and violent. Four thousand years ago a huge landslide blocked the Virgin River and formed a 350 foot-deep lake in Zion Canyon. This enormous slump block came off The Sentinel, so it’s called the Sentinel Slide.
The lake extended from Canyon Junction all the way to Angel’s Landing. Sediments settled out on the canyon floor, partly filling its natural V-shape. The river could not be stopped for long of course, and the natural dam was eventually breached. The resulting flood drained the lake and formed the V-shaped inner canyon between Court of the Patriarchs and Canyon Junction.
So now you know why Zion Canyon is flat-bottomed; it’s the old lake-bed. You can see the remains of the Sentinel Slide above you on the left as you drive up-canyon. For a closer view hike or go on a horse-back ride on the Sand Bench Trail, which climbs up on top of the slump block itself. By the way, the Sentinel Slide still acts up from time to time. In 1995, part of the old slide slipped, briefly blocking the river. The road was flooded for a time until the Virgin, never to be denied for long, re-established its channel.
Stay tuned for more from Zion National Park!