Rocks, Dinosaur Bones and Sea Fossils: Exploring Our Local Geology by Anne Janik

Searching for fossils in the sedimentary rock layers at the Dominquez-Escalante National Conservation Area located between Grand Junction and Delta. (Photo Credit: Anita Evans).

What kid hasn’t had some sort of rock collection? Discovering hidden gems is always a treat. Western Colorado is perfect for exploring geology with your kids. Look around − there is evidence of eons of geological happenings everywhere! 

Geology is an Earth science that investigates how the Earth formed and changes over time.  Through studying rock layers, geologists learn about the past and reconstruct the puzzle of Earth’s history. The Earth is a mind boggling 4.5 billion years old!  This ruler helps to grasp the age of the Earth. Each inch on the ruler stands for 375 million years (375,000,000 years). Because the numbers are so large, scientists use abbreviations for a billion years (BY) and a million years (MY). Major events in the Earth’s history are shown above the ruler and geologic ages (eons and eras) are marked below the ruler.
 

It might appear that the Earth’s surface never changes, but it is changing slowly all the time. Sediments, such as sand grains and clay, are deposited horizontally and then squeezed down by more sediment deposited on top. Over time, these layers turn into sedimentary rock with the oldest layers at the bottom and younger layers on top.  These rock layers constantly change over time, and with heat and pressure form metamorphic and igneous (volcanic) rock.  Melting or molten rock below the Earth’s surface builds up and breaks through older rock layers to form volcanoes. Metamorphic rock is formed when volcanic or sedimentary rock layers are buried and their structure changes under pressure - this is how diamonds are formed! Earthquakes occur when the Earth’s crust moves on the molten mantle like meringue on the surface of a lemon meringue pie. Cracks in the crust, called faults, can cause the Earth’s crust to move, fold, and tilt through a process called plate tectonics. Colliding plates can create mountain ranges and reshape the Earth’s continents. As the plates slowly shift across the globe, volcanoes and earthquakes represent the immense power at play. External events such as landslides and water or wind erosion wear down mountains, depositing the sediments downstream. 
 
Check out the last 1.6 inches of the 12-inch ruler (the Phanerozoic Eon). We know more about this time than any other in Earth’s history and we know that life was abundant! Many strange creatures swam, crawled, and flew across this corner of Colorado.  The story of these ancient creatures and where they lived are told by their fossils or impressions, bones, footprints, shells, petrified wood, and even fossilized feces, called coprolites, left behind in the rock layers. 
 
The present is the key to the past – this is the first lesson in geology, which means geologic events we observe today took place in the past. Volcanoes, earthquakes, floods, ocean tides, winds, gravity, as well as sedimentation and erosion  likely behaved similarly throughout time in shaping our landscapes. Glacial ice advances then melts; wind and water erode mountains until they are flat; valleys fill with rock and debris washed down from highlands. The Earth is and was a very dynamic place! 
 
Let’s look a little closer at Colorado’s geologic history. Most of Western Colorado lies within the Colorado Plateau. This high-desert formed millions of years ago when tectonic plates slowly pushed together, uplifting stacked layers of sand, silt, and mud to form the Plateau. Ancient volcanic mountains, plateaus, buttes, deeply carved canyons, and stunning color ranges are the defining characteristics of this region. The plateau is dominated by high mountains gashed by river canyons, dry washes, and intermittent stream beds. Near the southern end of the Plateau, the Grand Canyon has exposed rocks with ages that span almost 2 billion years.

Colorado National Monument was established because of its unique geology. Situated on the Uncompahgre Plateau (part of the larger Colorado Plateau), the monument was shaped over millions of years into colorful, wind-eroded sandstone formations, towering monoliths, and steep-walled canyons. The deeper rock layers span billions of years, with sedimentary layers covering the bottom-most metamorphic layer. Erosion continues to change this landscape with each storm creating wind- and water-sculpted rock formations with shape-inspired names like Window Rock, Pipe Organ, and Sentinel Spire. 
 
The geologic story of the Black Canyon of the Gunnison is one of uplift, volcanism, and the erosive force of water. Large volcanoes erupted on either side of the uplift about 30 million years ago, burying it in volcanic rock. As early as 2 million years ago, the Gunnison River began flowing in force through the soft volcanic rock. Over time, river flows eroded a deep canyon in the metamorphic rock. The canyon, at 2700 feet deep, is one of the deeper canyons in North America.

Another local geologic hot spot is located just outside of Delta Colorado. In the early 1970’s, 150-million year old fossils from the Jurassic period were found in the Dry Mesa Dinosaur Quarry on the Uncompahgre Plateau.  One of the most prolific sites of its time, the quarry revealed a unique chain of Upper Jurassic sedimentary rock (Morrison Formation) known for its high yield of dinosaur fossils.  What a yield! Over 4,000 bones from 30 different species were unearthed in the Quarry including two new species of dinosaur! Check out this informative activity booklet about the quarry finds developed by the Forest Service: The Jurassic World and Other Exciting Times in the Geological Past of Colorado, Grand Mesa, Uncompahgre, and Gunnison National Forests.

The geologic past of Colorado is a dynamic story and you don’t have to travel far to observe it.  Start with a visit to the Dinosaur Journey Museum in Fruita for interactive displays such as an earthquake simulator, a sandbox for making your own dinosaur tracks, and a “quarry site” where kids can uncover actual Jurassic dinosaur bones. There are over 15,000 fossil specimens in its collections. Design your own scavenger hunt to see if your child can find fossils reflecting our region's warm, moist environment (ferns) or when our town was at the bottom of a vast sea (shark teeth and fish fossils). Colorado has been at the bottom of an ocean several times, has been covered by ice, and has seen the rise and erosion of vast mountain ranges long before the Rocky Mountains of today were formed. The rock layers and fossil collections are there to demonstrate it, you just have to get out there and take a closer look!

Here are a few links for fun geology activities for kids:

• The Jurassic World and Other Exciting Times in the Geological Past of Colorado, Grand Mesa, Uncompahgre, and Gunnison National Forests.

• Geologic Activity- Colorado National Monument (https://www.nps.gov/colm/learn/nature/geologicactivity.htm)
• 40 playful ways to teach young kids about rocks (https://www.fantasticfunandlearning.com/30-playful-ways-to-teach-young-kids-about-rocks.html)
• 15 ways kids can study geology at home ( https://earthsciencejr.com/15-at-home-geology-projects-for-kids/)
• Fascinating Geology Activities for Kids  (littlebinsforlittlehands.com/geology-for-kids/)

• Geology STEM activities for kids (https://www.sciencebuddies.org/stem-activities/subjects/geology)
• Geologic Time Scale (https://earthsciencejr.com/15-at-home-geology-projects-for-kids/)
• Adapt this geology scavenger hunt for a local field trip area