RockTalk

Hazardous Soils in Colorado

This educational video, produced in 2011, explores the various problems that arise from hazardous soil conditions — expansive, collapsible/compressible,  hydrocompactive, dispersive, swelling/expansible — across the state. These geologic hazards combined cause more infrastructure damage in Colorado than any others. The video also covers the types of damage, methods for prevention or mitigation, along with outlining… Continue reading Hazardous Soils in Colorado

Case Study: Rockfall – St. Francis of Assisi, Castle Rock

A close-up showing the scale of one of the blocks of Castle Rock Conglomerate that is already displaced, Castle Rock, Colorado, January 1981. Photo credit: Colorado Geological Survey.

The CGS studied the site of St. Francis of Assisi Church in Castle Rock extensively after a block detached from the upper cliff face in January 1981. The block presented a risk to homes at the base of the slope south of the church, and was subsequently broken up using passive demolition methods. Other detached… Continue reading Case Study: Rockfall – St. Francis of Assisi, Castle Rock

The biggest, the best, the first, and the most diverse…

Free 8.5- x 11-inch map of Colorado geology (front) along with Geo-Whizology (back).

We have a free 8.5- x 11-inch (pdf) geologic map of Colorado containing Geo-Whizology of Colorado on the reverse side. Of course, we’re a bit biased, but we think Colorado has magnificent geology and it is beautifully displayed for all to see. The state holds many of the biggest, the best, the first, and the… Continue reading The biggest, the best, the first, and the most diverse…

Case Study: Rockfall – Glenwood Springs

Figure 3 -- This development in west Glenwood Springs constructed a rockfall impact wall above their townhomes to protect against both rockfall and mudslides (debris flows). Photo credit: Jon White for the CGS.

The town of Glenwood Springs in west-central Colorado lies at the confluence of the Roaring Fork and Colorado rivers. The town is tightly constrained by the steep river valleys so land-development pressure is causing residential growth to push into rockfall hazard areas. In West Glenwood, on the west side of the Roaring Fork River, the… Continue reading Case Study: Rockfall – Glenwood Springs

Case Study: Clear Creek Canyon rockslide

By August 2005, the entire rock slope had been laid back to 45 degrees along with the installation of stability-enhancing rock reinforcement anchors. Photo credit: Vince Matthews for the CGS.

Rockfalls and rock slides are common along transportation corridors in the Rocky Mountains. Clear Creek Canyon just west of Golden is one of the most active rockfall areas in Colorado. The canyon has been cut into Precambrian schists and gneisses by Clear Creek, one of the primary drainages in the Denver area. Rockfalls occur every… Continue reading Case Study: Clear Creek Canyon rockslide

Case Study: mine subsidence, CSM

Retaining wall settlement at the center of the image with the sorority houses in the background and the IM field in the foreground. Photo credit: T. C. Wait for the CGS.

For decades, the west side of the Colorado School of Mines (CSM) main campus had subsidence issues related to historical mining activities. At one point, in the 1990s, one of the married student housing units in that area was so badly damaged that it was condemned.  In the early 2000s, after the school converted the… Continue reading Case Study: mine subsidence, CSM

Dr. Cílek on the Bohemian karst

Bohemian karst (Český kras) landscape formed in a limestone of Silurian and mainly Devonian age. The area hosts several international stratotype and parastratotype sections, including the main Silurian/Devonian Global Boundary Stratotype Section at Suchomasty. Photo credit: Milos Sejn.

Dr. Cílek, the Director of the Czech Republic’s Academy of Sciences Institute of Geology delivers a fascinating talk about the Bohemian Karst region of the Czech Republic, around Beroun, that weaves the human historical, mystical, and mythological elements with the underlying geology and speleology. Most people don’t know that Colorado has a small but significant… Continue reading Dr. Cílek on the Bohemian karst

Case Study: Roaring Fork sinkhole

A large sinkhole opened in January 2005 at the Ironbridge Development and Golf Course, in the Roaring Fork River Valley, approx. 6 mi. (9.7 km) southeast of Glenwood Springs. Two golf carts inside the structure were lost down the throat of the sinkhole. View is to the northwest, towards the confluence of the Roaring Fork and Colorado rivers at Glenwood Springs. The red cliffs in the background are the Maroon Formation. For scale, note person in white hardhat standing in the snow. Photo credit: Jon White for the CGS.

[ED: This report from January 17, 2005 was written by Jon White, (Senior Engineering Geologist, Emeritus). Lightly edited for dated references it highlights a hazardous geological regime in the central Colorado Rockies around the Roaring Fork River Corridor.] Last week, while on the Western Slope, I was informed by a number of people that a… Continue reading Case Study: Roaring Fork sinkhole

Case Study: Avalanche – Silver Plume

Avalanche debris in the runout zone taken from a helicopter on the morning after the avalanche occurred, 24 March, 2003. Photo credit: Xcel Energy.

On March 23, 2003, a large avalanche occurred about one mile west of the Town of Silver Plume. The avalanche brought trees, rock, soil and snow to the valley floor, knocked down overhead utility lines, blocked the I-70 frontage road, damaged the town’s water treatment plant (WTP), and dammed Clear Creek. The dam was breached using explosives before the plant’s electric pump motors were flooded. With damage to the WTP’s chlorine contact tank and building, Silver Plume residents had to boil their tap water for over a month.

Case Study: Colorado Mountain College, Spring Valley

West view of the 2003 sinkhole showing proximity to campus buildings. Sunlight Ski Area is on the left horizon. Roaring Fork River valley is in left middle background below the ski area and in front of first row of ridges. Photo credit: Jon White for the CGS.

In early February of 2003, a 24-foot-wide (7.5 m) sinkhole spontaneously opened on a soccer field at the Colorado Mountain College (CMC) – Spring Valley campus, about 10 miles (16 km) southeast of Glenwood Springs in Garfield County. The CMC physical plant maintenance staff back-filled the hole with road pavement waste, but the sinkhole subsequently… Continue reading Case Study: Colorado Mountain College, Spring Valley

Swelling Soil Publication Wins Another National Award

SP-43 A Guide to Swelling Soils for Colorado Homebuyers and Homeowners

CGS Special Publication 43, SP-43 A Guide to Swelling Soils for Colorado Homebuyers and Homeowners, by Dave Noe, William “Pat” Rogers, and Candace Jochim, is the winner of the 2001 Edward B. Burwell, Jr. Award by the Geological Society of America, Engineering Geology Division. This prestigious award is made to the author(s) of a published… Continue reading Swelling Soil Publication Wins Another National Award

A Dash with Dinosaurs

The Purgatoire River dinosaur trackway at twilight, Otero County, Colorado. Photo credit: Martin Lockley.

In the next months, we will be sharing some unpublished field trip guides that we have made over the years. The occasion for this one was “Earth Science Week” back in 2000, an annual event initiated by the American Geological Institute (AGI). That year, scores of celebrations—field trips, demonstrations, lecture series, film series, exhibits, school… Continue reading A Dash with Dinosaurs

Case Study: Rockfall – Manitou Springs

A precarious rock above Manitou Springs started to move in 1995 after a period of wet weather. As an emergency measure, high-strength steel cables were wrapped around the rock and anchored to the surrounding ledge to arrest the movement. Photo credit Jon White for the CGS.

by Jon White Manitou Springs occupies a narrow valley where Fountain Creek emerges from the foothills northeast of Pikes Peak and west of Colorado Springs. The valley slopes are composed of interbedded resistant sandstone and conglomerates (i.e., gravelly sandstone), and weaker mudstones and shale. The outcropping sandstone is most prevalent on the steeper slopes on… Continue reading Case Study: Rockfall – Manitou Springs

Case Study: Denver – August 9, 1967

Isoseismal map for the earthquake north-east of Denver - 9 August 1967 - MMI VII. (detail) Kirkham, Robert M., and William P. Rogers. “Bulletin 52 - Colorado Earthquake Information, 1867-1996.” Earthquake. Bulletin. Denver, CO: Colorado Geological Survey, Division of Minerals and Geology, Department of Natural Resources, 2000. https://coloradogeologicalsurvey.org/publications/colorado-earthquake-information-1867-1996.

Major magnitude 5.3 earthquake shock in Denver   One of the strongest and most economically damaging earthquakes to affect the Denver area in the 1960s occurred on August 9, 1967 around 6:30 AM, awakening and frightening thousands of people. This magnitude 5.3 earthquake, centered near Commerce City, caused more than eight million dollars (2022 dollars)… Continue reading Case Study: Denver – August 9, 1967

Mines and Minerals: the early Survey

Historical postcard "Prospecting in Leadville", Colorado, date unknown. Photo credit: unknown.

While a number of brilliant men have in past years held the office of Colorado State Geologist, it is no disparagement to them to say that their work produced few tangible or lasting results. The fault was the state’s and her legislatures’ previous to that of 1907. Limited by niggardly appropriations for carrying on investigation… Continue reading Mines and Minerals: the early Survey

Concerns about the new survey

Boulder oil field, 1915. Photo credit: C. L. McClure and the Denver Public Library.

Regarding the Colorado Geological Survey (an article appearing in the Mining Reporter, March 1907): We note that one of our contemporaries, in recently commenting on the University bill creating a State Geological Survey of Colorado — the bill reported favorably on by the joint Senate and House mining committee — voices in no uncertain language… Continue reading Concerns about the new survey

Case Study: The Big One

HAZUS simulation: 1882 Earthquake, Rocky Mountain National Park Epicenter M 6.6, CEUS Attenuation

Colorado’s largest historic earthquake: November 7, 1882 – Magnitude 6.6 On Tuesday, November 7, 1882 at about 6:30 p.m. local Denver time, a moderately strong earthquake shook much of Colorado and parts of southern Wyoming and northeastern Utah. The following quote from the Rocky Mountain News gives an indication of the shaking in Denver, 60… Continue reading Case Study: The Big One