Field Trip to Grand Mesa

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This trip will take you to the summit of Grand Mesa. Here you will be in typical montane and subalpine ecosystems. Our trip begins at Land-of-Lakes where we will learn about the geology of the Grand Mesa. From there we will travel to Ward Creek where we will learn about aquatic biology. Be ready to get a little wet and learn a lot about invertebrates, fish, mountain geology and vegetation. We are taking ourhike in the middle of June. Off we go!

The Grand Mesa is located fifty-five miles east of Grand Junction, Colorado, and is the world's largest flat-top mountain. Our trip begins atMesa StateCollege. Heading north on 12th street, turn right on Horizon Drive to gain access to Interstate 70 heading east. The on ramp is located just behind Taco Bell on the right-hand side. Follow I-70 for approximately five miles to the Palisade exit. On the left, notice Mt. Garfield looming as the highest point in the Grand Valley.

Mt. Garfield has an elevation of 6,765 feet and a hike to the top provides a spectacular view of all the Grand Valley including the San Juans and Colorado National Monument in the south, the Manti La Sals to the west and the Grand Mesa to the east. Pull off the interstate at the Palisade exit for a brief discussion about the geology of the Bookcliffs. Make sure to notice hoodoos in the background. When stopped at the Palisade exit, look south of the interstate and notice the flat-topped hills scattered over the Valley. These hills are known as pediments and were deposited by the Colorado River as it meandered through the Valley before reaching its present day position. A closer look at these terraces would reveal that they are composed mainly of smoothed river pebbles, cobbles, and boulders. To the north of the interstate you will see a geologic group called the Bookcliffs.

The Bookcliffs extend from Rangely, Colorado, to central Utah near a town called Price. They were formed by a resistant sandstone layer from the Cretaceous Mesa Verde Formation that caps the softer Cretaceous Mancos Shale. The Mesa Verde Formation is composed of remnants from an ancient shoreline beach deposit. It's hard to believe that approximately 80 million years ago your home in Grand Junction would have been beachfront property and that about 100 million years ago it would have been underwater during the deposition of the Mancos Shale. The Mancos was deposited in a large shallow seaway that separated the eastern half of the United States from the western half. Grand Junction just happened to lie in the middle of this large sea. Evidence of this is found in the marine fossils that are in the Mancos Shale. After returning to the interstate, cross over the Colorado River and continue travelling east. We are now in De Beque Canyon. On both sides of the interstate you can see the old Cameo coal power plant and mine. Take exit 49 off the right-hand side of the road leading to Colorado Scenic Byway Highway 65. As you climb toward the summit of the Grand Mesa, watch as vegetation changes from one type to another. The first environment on the way is the juniper-piñon forest found at elevations of 5,000-6,500 feet.

Juniper is often referred to as cedar and along with piñon, cactus, andsage, it forms the high desert ecosystem you see on the left-hand side of the road on the rocky slopes of the canyon. Along the streambed you can find a riparian zone with tamarisk, cottonwood and willows growing along the water's edge. On the left-hand side petroglyphs from Fremont Indians can be seen from the road on flatrock surfaces between the turn offs to De Beque and Collbran. 

The geology of the canyon is relatively simple. The large cliffs you find are composed of the Hunter Canyon member of the Mesa Verde group, a late Cretaceous river system. Cross-stratification can be seen in the Hunter Canyon. We are now beginning to see a change of environment. Above the little town of Mesa begins the beautiful, montane ecosystem of quaking aspen.

Aspen are abundant on the Mesa between elevations of 8,000-10,000 ft. Their green foliage is renowned for the beautiful shades of orange, yellow and red in late autumn. After passing Powderhorn Ski Resort you begin to see fantastic views of the Valley below. You can now see large talus slopes of basalt lining the roadsides.

Basalt is an igneous rock formed when hot magma cools. The Mesa used to be an active site for volcanoes. The volcanoes here were not the violent cones of Mt. St. Helen's but more like the flowing lavas of Mauna Loa, Hawaii. This is a great stop for geology. From here you can see the effects of the slumping on the sides of the Grand Mesa.

The basalt forms a resistant cap rock on top of the softer Uinta and Green River Formations of lake and river system origin. As water moves down through the basalt and flows over the sides of the shales, the Uinta and Green River Formations are eroded away and can no longer hold up the basalt cap. The basalt then breaks away and falls down the side in a rotational style leaving a depression next to the sides of the Mesa. This is where most of the lakes are formed. Near roadsides, piles of boulders can be seen being used in a process called toe loading. These rock piles protect roads by slowing the erosional slumping processes mentioned earlier, creating a barrier of pressure against saturated soils that tend to slump off.

If you take a closer look at the basalt of the Grand Mesa you will be able to see small green to red crystals that look almost like quartz. This is a mineral known as olivine. This mineral is important to geologists because it indicates that the basalts originated deep within the Earth at depths below the crust and into the mantle. So this rock went through a long journey before reaching the surface of the Earth and carried with it good evidence of the composition of the Earth at depths we can not physically see. As you come to the top of the Grand Mesa you can notice how the vegetation has changed from the aspen groves to conifers. Predominant evergreens are the fir and the spruce. You can distinguish firs and spruce by differences in their cones and bark. Spruce have orange bark with cones that hold a more solid shape. Firs have gray bark and their cones break up into smaller pieces.

Land-of-Lakes is located at around 10,000 feet above sea level. Turn into the parking lot and walk the short path to the overlook. Here we find a subalpine ecosystem. The spectacular view shows the West Elk, San Juan, and Manti La Sal mountain ranges as well as the Black Canyon of the Gunnison and severallakes of the Grand Mesa. The Grand Mesa has nearly 300 natural lakes; how many can you see from here?

If you look to the east, you can see a basaltic ridge. This is called Crag Crest Trail and is a common afternoon adventure for many Colorado natives and tourists. Be ready for a hike if you want to explore it; the full loop of the hike is eleven miles long!

The dominant trees on the mountaintop are the fir and spruce. Here between the basalt flows you can find typical subalpine vegetation like wild strawberries and raspberries. These scrumptious berries can withstand extreme temperatures and provide a food source for animals like black bears, squirrels, and chipmunks. There are many flowering plants you can see here including: Colorado Columbine (our state flower), pasque flowers, sulfur flowers, tansy asters, mountain candytuft, violets, and dandelions. On the rocks, red and green lichens can also be found.

Plants in the subalpine must be able to withstand wind. They are often not very tall and are found hiding between rock crevices for protection. Annual precipitation is speculated torange from thirty to forty inches. The rocks that outcrop at the Land-of-Lakes area are smooth and rounded and, unlike many of the rocks we have previously seen, they exhibit glacial polish. This is a result of ice scraping away the top of therock until it is smooth.Basalt isa very hard rock and it would take something with a lot of power a long time to erode these rocks. A closer look reveals linear features in the rocks like grooves and scratches. Some are quite large while others are just barely visible.

 These grooves are glacial striations formed by rocks and debris that were frozen into the bottom of the glacier while it moved across the land. These striations give clues to the direction the glacier was moving. If a compass is set down directly next to and parallel with the striations, a bearing can be taken and when compared statistically with many other measurements from the area we can get a general idea of the direction the glacier was moving.

The Grand Mesa was occupied with glaciers most recently 10,000 years ago during the Pinedale Glacial Period and 15,000 years ago during the Bull Lake Glacial Period. Both of these glacial periods left behind evidence of the presence of glaciers not only in the form of striations but also in the form of moraines. Moraines are linear ridges found throughout the Grand Mesa that are composed of glacial till. Glacial till is a mixture of clay, sand, pebbles, boulders, and even larger pieces of rock that are very angular and not very well sorted.

A few examples of glacial till can be found along the road in the form of road cuts. Be looking for them on your way down. From here, we continue travelling across the Grand Mesa to our second stop, Ward Creek. Ward Reservoir is located at the top of the Grand Mesa at an elevation of 10,110 feet and has 84.0 surface acres making it the sixth largest lake on the Grand Mesa. The stream flowing into the lake from the north (left) is Ward Creek. Along the water's edge look for montane vegetation: false hellebore, bistort, pussy willow, buttercup, cinquefoil, clover, dandelion, marsh marigold, and lupine.

You may be thirsty but don't let the crystal clear water fool you; it is not safe to drink. Hiding under the water you can find invertebrates clinging to rocks and algae: stoneflies, mayflies, caddis flies, simulids, water beetles, crane fly larva, and mosquito larva. The use of an insect net can help you get a better look at the tiny creatures.

On the water's surface look for water striders and backswimmers. In shallow pools watch for fish including several trout species (brook, Colorado cutthroat, lake, rainbow, and brown trout), flannel mouth suckers, white suckers, Colorado bluehead suckers, and mountain white fish. Test your speed against these fast swimmers by trying to catch them in a seine or fish net. Don't be afraid to get a little wet!

  After all your energy is gone, pick a soft spot on the grassy water's edge to enjoy your lunch and learn a little history of the Grand Mesa. Once called "Thunder Mountain" by the Ute Indians, the Grand Mesa has always been abundant with plant and animal life. Common large animals include elk, deer, mountain lion, bobcat, beaver, porcupine, andblack bear. Small mammals like mice, squirrels, martens, marmots, chipmunks, mountain cottontails, andwoodrats are also common. Some birds that can be found include mountain bluebirds, chickadees, jays, finches, grouse, hawks, and owls. The abundance of these animals and the availability of shelter and water made the Grand Mesa a comfortable living environment for ancient peoples who lived here as many as 10,000 years ago. We hope you liked our trip up the Grand Mesa. It is a great place to learn about aquatic biology, mountain ecosystems and geology.

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