News/Features 11/07/99

Think of Logan Canyon as an ancient aquarium turned to stone

By Emily Parkinson

Jim Balls of Hyde Park, left, and Troy Jensen of North Logan pause in front of a limestone outcropping on the Crimson Trail in Logan Canyon in early October. Sudden changes in climate and eons of geologic action have formed the face of Logan Canyon. / Photo by Cameron Bailey.

Editor's note: This story was produced for the USU mass communication class "Beyond the Inverted Pyramid," COMM 3110.

Our journey begins at the mouth of Logan Canyon. Picture yourself walking along the riverside, looking up toward the sky to see the masses of earth and stone that project upward.

The mountains are covered with Christmas tree pines standing tall, in blue and green, guardians of the mountain, looking over the canyon with a watchful eye. Joining the pines stand the quaking aspens with their slender trunks of white with black splotches. The striking colors of the tree trunk are topped with a cluster of green that glows in the sunlight as the leaves dance in the wind.

These trees are accompanied by thousands of elements that have been shifted and transported by the forces of nature in order to present the canyon as it is today. Nature is constantly in motion. Some changes cannot be seen with the naked eye, while others can. The mountains create the valleys, and the rivers create the canyons. How does this occur?

Nature's artwork has been created over centuries of geological and climatic changes. Cache Valley was once at the bottom of Lake Bonneville, a freshwater inland lake that formed about 70,000 years ago. The features of Lake Bonneville are fairly obvious to the casual observer. Looking south across the Logan River and east to the mouth of Logan Canyon, there are several distinct benches, which are shoreline features formed by the ancient lake.

According to Susan Morgan, author of Geologic Tours of Northern Utah, Lake Bonneville was roughly 10 times the size of the Great Salt Lake. Fifteen thousand years ago, it had a surface area of about 20,000 square miles, approximately one fourth the size of Utah. Its depth was about 1,000 feet. Lake Bonneville had an abundance of aquatic life including cutthroat trout, Utah chub fish, snails, clams and algae.

Lake Bonneville eventually rose high enough to overflow its basin and flood into the Snake River drainage. The site of this overflow is Red Rock pass, 14 miles northwest of Preston, Idaho. The flood carved out a huge gorge through the Snake River's course in Idaho and out to the Pacific Ocean in just a few weeks. The flood lowered the lake 350 feet, leaving the shore approximately at the bench by Utah State University. The lake remained at this level from 14,000 to 13,000 years ago.

About 11,000 years ago, evaporation increased from Lake Bonneville, causing it to become hotter and to recede, leaving the dry shoreline. As this took place, the waters retreated out of Cache Bay. Huge amounts of sand were left behind, and the Bear River cut through the delta in the northern part of Cache Valley, moving large amounts of sand out onto the lake-bottom clay and silts in the valley.

"Driving through the mouth of Logan Canyon, you can see layered sedimentary rocks, which are rocks from the early Paleozoic era (500 million to 300 million years ago)," said Morgan. "Logan Canyon is much younger than the rocks seen in it."

The mountains that we see today began forming millions of years ago. Logan Canyon may be considered to be an ancient aquarium turned to stone. During ancient times, the Logan area was almost continually under a giant, shallow, inland ocean. Today, layers that have accumulated over 300 million years represent 30,000 feet of soft deposits before they accumulated into solid rock.

As you travel up Logan Canyon, there are several signs of rock formation that can be easily spotted. As you stand on the bridge at the entrance to Spring Hollow Campground, facing north across U.S. 89, you can see sedimentary rocks formed from the weathered debris of other rocks laid down in layers. The transition from one type of rock to the next one laid down on top of it, occurred as the level of the Devonian Sea, which covered this area about 375 million years ago, rose and fell. As you look at the rock from Spring Hollow, the layers are flat; however, looking toward the mouth of the canyon, the rock layers dip to the east, and looking toward the top of the canyon, the layers begin to dip to the west. At Spring Hollow you are standing at the lowest point of a giant fold in the earth, which forms a bowl shape that inclines on both sides of Spring Hollow. This is the axis of the Logan syncline.

One of Logan Canyon's oldest treasures is at the end of a five-mile hike that gives you a bird's eye view of the entrenched meanders of the Logan River. The trailhead starts at the end of Wood Camp road, which is about 15 miles up Logan Canyon. The trail takes you on a five-mile journey through a variety of dense trees as well as wide-open spaces. The Jardine Juniper tree has been found to be about 3,200 years old. Although many of its limbs are dead, the tree still lives and seems to be literally growing out of solid rock. It is the oldest known Rocky Mountain juniper in Cache Valley. The juniper is admired for its strength and perseverance as it continues to stand tall, several hundred feet above U.S. 89 on the canyon floor.

Maurice Linford discovered Jardine Juniper on July 23, 1923. Linford was a botany student at Utah State Agricultural College. The tree was named in honor of William J. Jardine, an alumnus of USAC, who was secretary of agriculture in President Hoover's Cabinet.

Avalanches have helped to form the canyon as we see it today. Vegetation can tell you if you are in an area that has been hit by an avalanche. There maybe patches of open slope between vegetated areas, missing branches on the uphill side of trees, or marked differences in the height of trees.

Conglomerate looks like

pudding with raisins

and grapes mixed in.

Temple Fork is one of several side canyons that branch off from Logan Canyon. The Wasatch formation found in Temple Fork is made of red conglomerate and sandstone dated to the Tertiary age, which was between 58 million and 5 million years ago. Most of the rock that you find there is smooth and round, caused by the constant agitation from surrounding water. The Wasatch formation contains a lot of red color, caused by the iron in the rock that has gotten wet, and turned red from reaction with the oxygen in the water to form iron oxide. Another common feature of this formation is the Knight Conglomerate. The conglomerate stone looks like pudding with raisins and grapes mixed in, thus acquiring the nickname "pudding stone." You can also find this stone at the base of the red cliffs south of Tony Grove Lake and at the Red Banks campground.

Earth slides and flows, rockfalls and avalanches all contribute to mass wasting, which is the downslope movement of rock and unconsolidated material under the influence of gravity. On a geologic scale, mass wasting has to do with decay and abandonment. Many of the hills, broken slopes and piles of broken rock in the Temple Fork area result in slides, flows, falls and avalanches. The loose materials of the Wasatch are prone to the influence of water and gravity, which is especially evident in Temple Fork.

The canyon is constantly changing. Perhaps several millions of years from now, our rugged mountains will be weathered down to rolling hills, much like the Appalachians.

"The mountains here are very young still, only about 10 million years old," Morgan said. "In another 10 million years, there is the potential that our mountains will start to flatten, but the river will continue to cut the canyon deeper." It is hard to predict how the canyon will shift and change through time.

"A basic premise of geology is the concept that what happens today also happened in the past," Morgan said. "Present events provide a key to the past. The geologic phenomena occurring today may be sudden, such as a volcanic eruption or a debris flow. Most processes are very slow, however, such as erosion of a river valley, requiring thousands and millions of years to produce change on the earth's surface."

One of Logan Canyon's oldest treasures is at the end of a five-mile hike that gives you a bird's eye view of the entrenched meanders of the Logan River. The trail starts at the end of Wood Camp road and takes you through a variety of dense trees and wide-open spaces. At the top, the Jardine Juniper seems to be literally growing out of solid rock. / Photo by Mike Sweeney




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