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🚙 Located 9.3 miles up the canyon from the intersection of Colorado Bvd. and US 14A at Spearfish GPS Coordinates N 44.23.577 W 103.54.715 4,796 ft.
Gravitational Greetings Update 3.pdfIn–Depth Geology Lesson pdf
A great document to print for those who want to dig deeper into the geologic story.
Tumbling down from crags above
With seismic-level force.
The giant boulders came to rest
Within the Spearfish course.
Field Exploration
Field Exploration
Was that thunder I just heard or the sound of two giant boulders crashing into a riverbed? In this Spearfish Canyon exploration we take a look at the remnants of a rockfall event that took place in 1994. The sheer size of the boulders will amaze and the cause of the event will be investigated. Stay alert as you "Watch for Fallen Rock."
This pdf Lesson Guide contains the specific directions for reaching our featured site as well as a detailed explanation of its geologic story for those desiring more depth. Mileage and coordinates are provided in each document and roadmaps and other learning aids can be found at the Geologic Resources link in the sidebar menu. The document is most useful if you have it in hand at the geologic site. Exercise extreme caution at the lesson site and along roadways.
Are you ready. . . . Let's Go! S. V. Fogarty & W. R. Stevens
Site Access
When traveling from the north look for two large boulders lying directly in Spearfish Creek to the left of the highway. They will be clearly visible and will be lying very close to the road itself along the inside of a curve. About 500 feet past the boulders, and also on your left, you’ll find a small paved turnout where you can park. For safety reasons we would advise you to perform a “drive-by” to identify the turnout and then return to park. As you walk back to the boulders from the turnout please stay well clear of the roadway. There is a narrow and somewhat gnarly trail that leads from the parking area and through some trees that you can follow but watch out for poison ivy. If you choose to walk along the roadway, stay well to the side and then carefully descend to the level of Spearfish Creek as soon as safely possible so as to stay clear of the traffic.
The Kissing Rocks
The Kissing Rocks
Limestone boulders from the 1994 rockfall event came to rest alongside the highway in the Spearfish Creek channel.
Limestone boulders from the 1994 rockfall event came to rest alongside the highway in the Spearfish Creek channel.
The Kissing Rocks Viewed From Above
The Kissing Rocks Viewed From Above
Drone photo taken at an altitude of ~175 ft. AGL. Compare boulders to highway for scale.
The Kissing Rocks Underpass
The Kissing Rocks Underpass
Spearfish Creek flows between the two large boulders creating a natural eyelet.
Note the lighter colored rock exposure in the upper cliff of Pahasapa Limestone. This marks the original location of the boulders before becoming detached and falling to the valley floor. Examination of the landslide chute shorty after the event revealed that an unfortunate deer had been caught directly in the path of the tumbling boulders. Note the position of the Pahasapa Formation in the Stratigraphic Column to the right.
Note the lighter colored rock exposure in the upper cliff of Pahasapa Limestone. This marks the original location of the boulders before becoming detached and falling to the valley floor. Examination of the landslide chute shorty after the event revealed that an unfortunate deer had been caught directly in the path of the tumbling boulders. Note the position of the Pahasapa Formation in the Stratigraphic Column to the right.
Note the position of the Pahasapa Limestone in the diagram above. Due to its high permeability and porosity, considerable amounts of water enter the Pahasapa Limestone and make it susceptible to weathering. Landslides such as this are common in the canyon but this one's proximity to the highway makes for an exceptional observational opportunity. Age and thickness are approximates.
Cliff Face Scar
Cliff Face Scar
Photo taken ~250ft. above the valley floor. Note the fresher-looking rock exposure near the lower center of the photo. This marks the attachment point of the boulders before falling. We personally don't know if one large mass fell and then fragmented upon impact or if each boulder broke off and fell independently. Fun to think about, though!
There's more to this story than meets the eye. Download our In-Depth Lesson pdf above if you desire a more thorough coverage.
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