Aug 142017
 
Dramatic landslide headscarp threatens this structure on Constellation Drive in Skyway, Colorado Springs, Colorado, May 2017. Photo credit: Jon Lovekin, PG.

Dramatic landslide headscarp threatens this structure on Constellation Drive in Skyway, Colorado Springs, Colorado, May 2017. Photo credit: Jon Lovekin, PG.

The city of Colorado Springs lies at the boundary between the Great Plains and the Front Range of the southern Rocky Mountains. Western sections of the city are underlain by weak claystones and shales that are prone to landslides. Several developed areas have experienced various degrees of damage from landslide movements during the 1990s and over the last several years. These landslides were widely reported in the press; however, it is apparent that significant segments of the general public are not aware that they reside in areas with landslide hazards. The purpose of this symposium is to help educate the public about the inherent risks, liabilities, and responsibilities of both living in and developing such terrain.

WHAT

A free public symposium featuring a panel of experts will include informative presentations on landslide hazard risk, disclosure requirements for sellers and agents, construction requirements under the city’s revised geologic hazard ordinance, home warranties, and more.

Held in conjunction with the annual meeting of the Association of Environmental and Engineering Geologists, there is no cost or preregistration requirement but seating is limited. If you wish to attend other AEG events you will need to preregister and pay a registration fee.

WHERE

Carson Room, Antlers Hotel, Downtown Colorado Springs, Colorado

WHEN

September 15, 2017, 9:00 AM – 12:00 NOON

SCHEDULE

8:45 am — Doors Open (seating is first-come-first-serve!)

9:00 am — Opening Remarks, Mayor John Suthers, City of Colorado Springs

9:20 am — Jon White, Senior Geologist, Colorado Geological Survey: Landslide Susceptibility in the Colorado Springs Area — Geology and History

10:00 am — Marcia Waters, Director of the Division of Real Estate, Colorado Department of Regulatory Agencies: Real Estate Disclosure Requirements

10:20 am — Robert Moore, Risk Management Engineer: 2-10 Home Buyers Warranty, Requirements for Colorado Springs Landslide Susceptibility Zone

10:40 am — Don Knight and Tom Strand, Council members, City of Colorado Springs: Public Policy and Landslides, Revising the City’s Geologic Hazard Ordinance

11:20 am — Peter Wysocki, City of Colorado Springs Planning Director: New Requirements for Developing in Geologic Hazard Areas

11:40 — Panel Discussion

Jul 092017
 

Earthquakes strike suddenly, violently, and without warning. While Colorado is not as seismically active as some places, it does have a history of earthquake activity. Identifying potential hazards ahead of time and advance planning can reduce the dangers of serious injury or loss of life from an earthquake. Repairing deep plaster cracks in ceilings and foundations, anchoring overhead lighting fixtures to the ceiling, and following local seismic building standards, will help reduce the impact of earthquakes.

Six Ways to Plan Ahead

1.) Check for Hazards in the Home
  • Fasten shelves securely to walls.
  • Place large or heavy objects on lower shelves.
  • Store breakable items such as bottled foods, glass, and china in low, closed cabinets with latches.
  • Hang heavy items such as pictures and mirrors away from beds, couches, and anywhere people sit.
  • Brace overhead light fixtures.
  • Repair defective electrical wiring and leaky gas connections. These are potential fire risks.
  • Secure a water heater by strapping it to the wall studs and bolting it to the floor.
  • Repair any deep cracks in ceilings or foundations. Get expert advice if there are signs of structural defects.
  • Store weed killers, pesticides, and flammable products securely in closed cabinets with latches and on bottom shelves.
2.) Identify Safe Places Indoors and Outdoors
  • Under sturdy furniture such as a heavy desk or table.
  • Against an inside wall.
  • Away from where glass could shatter around windows, mirrors, pictures, or where heavy bookcases or other heavy furniture could fall over.
  • In the open, away from buildings, trees, telephone and electrical lines, overpasses, or elevated expressways.
3.) Educate Yourself and Family Members
  • Contact your local emergency management office or American Red Cross chapter for more information on earthquakes. Also read the “How-To Series” for information on how to protect your property from earthquakes.
  • Teach children how and when to call 9-1-1, police, or fire department and which radio station to tune to for emergency information.
  • Teach all family members how and when to turn off gas, electricity, and water.
4.) Have Disaster Supplies on Hand
  • Flashlight and extra batteries.
  • Portable battery-operated radio and extra batteries.
  • First aid kit and manual.
  • Emergency food and water.
  • Nonelectric can opener.
  • Essential medicines.
  • Cash and credit cards.
  • Sturdy shoes.
5.) Develop an Emergency Communications Plan
  • In case family members are separated from one another during an earthquake (a real possibility during the day when adults are at work and children are at school), develop a plan for reuniting after the disaster.
  • Ask an out-of-state relative or friend to serve as the “family contact.” After a disaster, it’s often easier to call long distance. Make sure everyone in the family knows the name, address, and phone number of the contact person.
6.) Help Your Community Get Ready
  • Publish a special section in your local newspaper with emergency information on earthquakes. Localize the information by printing the phone numbers of local emergency services offices, the American Red Cross, and hospitals.
  • Conduct a week-long series on locating hazards in the home.
  • Work with local emergency services and American Red Cross officials to prepare special reports for people with mobility impairments on what to do during an earthquake.
  • Provide tips on conducting earthquake drills in the home.
  • Interview representatives of the gas, electric, and water companies about shutting off utilities.
  • Work together in your community to apply your knowledge to building codes, retrofitting programs, hazard hunts, and neighborhood and family emergency plans.

What To Do During an Earthquake

Stay as safe as possible during an earthquake. Be aware that some earthquakes are actually foreshocks and a larger earthquake might occur. Minimize your movements to a few steps to a nearby safe place and stay indoors until the shaking has stopped and you are sure exiting is safe.

If indoors
  • DROP to the ground; take COVER by getting under a sturdy table or other piece of furniture; and HOLD ON until the shaking stops. If there isn’t a table or desk near you, cover your face and head with your arms and crouch in an inside corner of the building.
  • Stay away from glass, windows, outside doors and walls, and anything that could fall, such as lighting fixtures or furniture.
  • Stay in bed if you are there when the earthquake strikes. Hold on and protect your head with a pillow, unless you are under a heavy light fixture that could fall. In that case, move to the nearest safe place.
  • Use a doorway for shelter only if it is in close proximity to you and if you know it is a strongly supported, load-bearing doorway.
  • Stay inside until shaking stops and it is safe to go outside. Research has shown that most injuries occur when people inside buildings attempt to move to a different location inside the building or try to leave.
  • Be aware that the electricity may go out or the sprinkler systems or fire alarms may turn on.
  • DO NOT use the elevators.
If outdoors
  • Stay there.
  • Move away from buildings, streetlights, and utility wires.
  • Once in the open, stay there until the shaking stops. The greatest danger exists directly outside buildings, at exits, and alongside exterior walls. Many of the 120 fatalities from the 1933 Long Beach, California earthquake occurred when people ran outside of buildings only to be killed by falling debris from collapsing walls. Ground movement during an earthquake is seldom the direct cause of death or injury. Most earthquake-related casualties result from collapsing walls, flying glass, and falling objects.
If in a moving vehicle
  • Stop as quickly as safety permits and stay in the vehicle. Avoid stopping near or under buildings, trees, overpasses, and utility wires.
  • Proceed cautiously once the earthquake has stopped. Avoid roads, bridges, or ramps that might have been damaged by the earthquake
If trapped under debris
  • Do not light a match.
  • Do not move about or kick up dust.
  • Cover your mouth with a handkerchief or clothing.
  • Tap on a pipe or wall so rescuers can locate you. Use a whistle if one is available. Shout only as a last resort. Shouting can cause you to inhale dangerous amounts of dust.

What To Do After an Earthquake

  • Expect aftershocks. These secondary shockwaves are usually less violent than the main quake but can be strong enough to do additional damage to weakened structures and can occur in the first hours, days, weeks, or even months after the quake.
  • Listen to a battery-operated radio or television. Listen for the latest emergency information.
  • Use the telephone only for emergency calls.
  • Open cabinets cautiously. Beware of objects that can fall off shelves.
  • Stay away from damaged areas. Stay away unless your assistance has been specifically requested by police, fire, or relief organizations. Return home only when authorities say it is safe.
  • Be aware of possible tsunamis if you live in coastal areas. These are also known as seismic sea waves (mistakenly called “tidal waves”). When local authorities issue a tsunami warning, assume that a series of dangerous waves is on the way. Stay away from the beach.
  • Help injured or trapped persons. Remember to help your neighbors who may require special assistance such as infants, the elderly, and people with disabilities. Give first aid where appropriate. Do not move seriously injured persons unless they are in immediate danger of further injury. Call for help.
  • Clean up spilled medicines, bleaches, gasoline or other flammable liquids immediately. Leave the area if you smell gas or fumes from other chemicals.
  • Inspect the entire length of chimneys for damage. Unnoticed damage could lead to a fire.
  • Inspect utilities.
  • Check for gas leaks. If you smell gas or hear blowing or hissing noise, open a window and quickly leave the building. Turn off the gas at the outside main valve if you can and call the gas company from a neighbor’s home. If you turn off the gas for any reason, it must be turned back on by a professional.
  • Look for electrical system damage. If you see sparks or broken or frayed wires, or if you smell hot insulation, turn off the electricity at the main fuse box or circuit breaker. If you have to step in water to get to the fuse box or circuit breaker, call an electrician first for advice.
  • Check for sewage and water lines damage. If you suspect sewage lines are damaged, avoid using the toilets and call a plumber. If water pipes are damaged, contact the water company and avoid using water from the tap. You can obtain safe water by melting ice cubes.

Refer to Federal Emergency Management Agency‘s earthquake preparedness web site for further information.

Jul 032017
 

Nearly 100 potentially hazardous faults have been identified in Colorado. Generally, these are faults thought to have had movement within about the past 2 million years. There are other faults in the state that may have potential for producing future earthquakes. Because the occurrence of earthquakes is relatively infrequent in Colorado and the historical earthquake record is relatively short (only about 130 years), it is not possible to accurately estimate the timing or location of future dangerous earthquakes in Colorado. Nevertheless, the available seismic hazard information can provide a basis for a reasoned and prudent approach to seismic safety.

Faulting

Sudden movement on long faults is responsible for large earthquakes. By studying the geologic characteristics of faults, geoscientists can often determine when the fault last moved and estimate the magnitude of the earthquake that produced the last movement. In some cases it is possible to evaluate how frequently large earthquakes occurred on a specific fault during the recent geological past.

Geological studies in Colorado have discovered about 100 faults that moved during the Quaternary Period (past 2 million years) and could be considered potentially active. The Sangre de Cristo fault, which lies at the base of the Sangre de Cristo Mountains along the eastern edge of the San Luis Valley, and the Sawatch fault, which runs along the eastern margin of the Sawatch Range, are two prominent and potentially active faults in Colorado. However, not all of Colorado’s potentially active faults are in the mountains. For example, the Cheraw fault, which is in the Great Plains Physiographic Province in southeast Colorado, appears to have had multiple movements during the recent geologic past. Some potentially active faults cannot be seen at the earth’s surface. The Derby fault near Commerce City lies thousands of feet below the earth’s surface. It has not been recognized at ground level, and for that reason it is not included on the CGS Earthquake and Late Cenezoic Fault and Fold Map Server [1].

Screen-shot from the Earthquake and Late Cenezoic Fault and Fold Map Server.

Screen-shot from the Earthquake and Late Cenezoic Fault and Fold Map Server.

Several potentially active faults in Colorado are thought to be capable of causing earthquakes as large as magnitude 7.2 based on recent detailed studies. In comparison, California has hundreds of hazardous faults, one or two of which can cause earthquakes of magnitude 8.0 or larger. The time interval between large earthquakes on faults in Colorado is generally much longer than on faults in California.

Past and Possible Future Earthquakes

About 400 earthquake tremors of magnitude 2.5 or higher have been reported in Colorado since 1867. More earthquakes of magnitude 2.5 to 3.0 probably occurred during that time, but were not recorded because of the sparse distribution of population and limited instrumental coverage in much of the state. The largest known historical earthquake in Colorado occurred on November 7, 1882 and had an estimated magnitude of 6.6. The location of this earthquake probably was in the northern Front Range.

Although many of Colorado’s earthquakes occurred in mountainous regions of the state, some have been located in the western valley and plateau region or east of the mountains. The best known Colorado earthquakes were a series of events in the 1960s that were later shown to be triggered by the injection of liquid waste into a deep borehole at the Rocky Mountain Arsenal. Twelve of the so-called “Arsenal” earthquakes caused damage, including a magnitude 5.3 earthquake on August 9, 1967 that resulted in more than a million dollars in damage in Denver and the northern suburbs. This series of earthquakes continued for about ten years and was followed by about six years of quiescence. Earthquake activity resumed in the northeast Denver area in 1978, including a magnitude 4.3 event on April 2, 1981.

Colorado’s earthquake hazard is similar to other states in the intermountain west region. It is less than in states like California, Nevada, Washington, and Oregon, but greater than many states in the central and eastern United States. It is prudent to expect future earthquakes as large as magnitude 6.6, the largest historical event in Colorado.

Conclusions and Recommendations

Based on Colorado’s historical earthquake record and geologic studies, an event as large as magnitude 6.5 to 7.2 could occur somewhere in the state. Scientists are unable to accurately predict when the next major earthquake will take place in Colorado; only that one will occur. The major factors that prevent the prediction of the timing and location of future damaging earthquakes are the limited knowledge of potentially active faults and short historical record of earthquakes. Given Colorado’s continuing active economic growth and the accompanying expansion of population and infrastructure, it is prudent to continue the study and analysis of earthquake hazards. Existing knowledge should be used to incorporate appropriate levels of seismic safety into building codes and practices. Seismic safety of critical facilities and vulnerable structures is especially important. Emergency response and recovery planning should consider earthquake hazards and risk. Concurrently, we should expand earthquake monitoring, geological and geophysical research, and mitigation planning and activities.

References:

[1] Kirkham, R. M., W. P. Rogers, L. Powell, M. L. Morgan, V. Matthews, and G. R. Pattyn. “Bulletin 52B – Earthquake and Late Cenezoic Fault and Fold Map Server.” Earthquake. Bulletin. Denver, CO: Colorado Geological Survey, Department of Natural Resources, 2004.

Jun 272017
 
OF-16-02 Geologic Map of the Watkins Quadrangle, Arapahoe and Adams Counties, Colorado

We’ve just uploaded the next of our free STATEMAP quadrangle map products to our online store: the Geologic Map of the Watkins Quadrangle, Arapahoe and Adams Counties, Colorado. The STATEMAP series in general provides a detailed description of the geology, mineral and ground-water resource potential, and the geologic hazards of an area. Digital PDF/ZIP download.

Location of the Watkins Quadrangle, Arapahoe and Adams Counties, Colorado.

Location of the Watkins Quadrangle, Arapahoe and Adams Counties, Colorado.

Matt Morgan, Senior Research Geologist and CGS Deputy Director, along with Senior Engineering Geologist (Emeritus) Jon White generated this map with special input from Richard Madole (surficial geology) and Shannon Mahan (OSL analysis), both of the USGS. This free release from the CGS includes two PDF plates (with a geologic map, cross-section with correlation, oblique 3D view, and legend) along with the corresponding GIS data package that allows for digital viewing, all in a single ZIP file.

This mapping project was funded jointly by the U.S. Geological Survey through the STATEMAP component of the National Cooperative Geologic Mapping Program, which is authorized by the National Geologic Mapping Act of 1997, and also by the CGS using the Colorado Department of Natural Resources Severance Tax Operational Funds. The CGS matching funds come from the severance paid on the production of natural gas, oil, coal, and metals. Geologic maps produced through the STATEMAP program are multi-purpose information sources useful for land-use planning, geotechnical engineering, geologic-hazard assessment, mineral-resource development, and ground-water exploration.

This particular 7.5-minute, 1:24,000 quadrangle is situated within the Denver Basin, a Laramide-age structural basin that is an important resource for water along with oil & gas. Growth of the Denver Metro area is occurring in the northern half of the quadrangle which is crossed by Interstate 70 and is minutes from Denver International Airport. Dips within the quadrangle typically range from 3° to 7° to the N-NE which reflects the regional structural dip of the basin. Bedrock units consist of the lower part of the Dawson Arkose and the Denver Formation. The widespread Dawson Arkose is white to tan in color and composed of cross-bedded arkoses, pebbly arkoses and arkosic pebble conglomerates with sparse claystone and siltstone beds. The arkoses were shed off the uplifting Front Range into the subsiding Denver Basin during the latter phases of the Laramide Orogeny. Cobble-rich conglomeratic lenses were recognized in the lower part of the Dawson Arkose and represent localized flooding events in a typically quiet fluvial environment. The Denver Formation is finer grained, more clay rich, and yellower in color than the overlying Dawson Arkose and is part of a low-energy alluvial plain environment also related to the Laramide. The units are separated by a basin-wide, yet occasionally discontinuous variegated paleosol that is a regional unconformity and an important time-stratigraphic marker at the Paleocene-Eocene boundary.

Surficial deposits consist of middle Pleistocene to Holocene flood-plain and terrace-forming alluviums and Holocene sand deposits of predominantly eolian origin. The sand deposits are composed of disaggregated sediments derived from the weathering and subsequent mobilization of the underlying Dawson Arkose. New Optically Stimulated Luminescence (OSL) ages, collected during this project, indicate that these eolian deposits were first active during the lowermost Holocene. High-level gravel deposits of Neogene-early Quaternary age cap isolated buttes in the southern half of the quadrangle. These gravels consist of cobbles and boulders of granite, quartzite, sandstone and tuffaceous igneous rocks and were likely derived from the erosion of the late Eocene Castle Rock Conglomerate.

Citation: Morgan, Matthew L., and Jonathan L. White. “OF-16-02 Geologic Map of the Watkins Quadrangle, Arapahoe and Adams Counties, Colorado” Geologic. Open File Reports. Golden, CO: Colorado Geological Survey, 2016.
Jun 192017
 

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 the north side of the valley.

During the wet spring of 1995, rockfall and landslides incidents increased throughout Colorado, some resulting in fatalities. In Manitou Springs, a fortunate set of circumstances occurred before the Memorial Day holiday weekend when local residents observed the movements of a large, dangerous block of rock before it actually could fall. The observation set into motion an emergency declaration by the town, resulting in a compulsory evacuation of homes located below the rocky slope, the closing of the road in the area, and an immediate rock stabilization project. During this emergency situation, the Colorado Geological Survey was asked to provide expert assistance to help stabilize the rock. The emergency evacuation decree remained in effect until the rock was stabilized and the area subsequently declared safe.

The ledge of jointed sandstone along with several large displaced blocks is seen at the center of the image. Photo credit Jon White.

The ledge of jointed sandstone along with several large displaced blocks is seen at the center of the image. Photo credit Jon White.

A prominent 12-foot-thick ledge of strongly-jointed sandstone forms the rim of this slope. Two essentially vertical and intersecting joint sets produce large orthogonal sandstone blocks that are being undermined by the more easily weathered mudstone beds below the ledge. The blocks begin to topple as the underlying rock that supports them erodes, creating dangerous overhangs. At the time of discovery, this particular block had moved 5.5 feet from the back face of the sandstone ledge and tilted precariously over the next sandstone ledge below. Had the 70-ton block fallen, it would have certainly crushed a home below.

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.

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.

The extremely unstable, tilted, rock could not be removed due to the proximity of homes directly below, so high-strength steel cables were wrapped around the rock and anchored to the surrounding ledge. Once the block was safely restrained, additional cables were physically attached to the top of the block at anchor points that were cemented into drill holes to provide an additional level of support for the block and safety for the homes below.

After the rock was stabilized, additional cables were physically attached to the top of the rock block and secured to surrounding stable rock. Photo credit Jon White.

After the rock was stabilized, additional cables were physically attached to the top of the rock block and secured to surrounding stable rock. Photo credit Jon White.

May 162017
 

The Association of American State Geologists announced that their annual John C. Frye Memorial Award for 2017 is granted to the CGS and the staff members who authored the report The West Salt Creek Landslide: A Catastrophic Rockslide and Rock/Debris Avalanche in Mesa County, Colorado (CGS Bulletin-55). Utilizing a rich field data set, the report includes a comprehensive review of the geologic history of the area and presents a detailed timeline of the events surrounding the “the longest landslide in Colorado’s historical record.”

White, Jonathan L., Matthew L. Morgan, and Karen A. Berry. “Bulletin 55 - The West Salt Creek Landslide: A Catastrophic Rockslide and Rock/Debris Avalanche in Mesa County.” Bulletins. Golden, CO: Colorado Geological Survey, 2015. Bulletin 55.

White, Jonathan L., Matthew L. Morgan, and Karen A. Berry. “Bulletin 55 – The West Salt Creek Landslide: A Catastrophic Rockslide and Rock/Debris Avalanche in Mesa County.” Bulletins. Golden, CO: Colorado Geological Survey, 2015. Bulletin 55.

History of the Award:

Environmental geology has steadily risen in prominence over recent decades, and to support the growth of this important field, the Frye Award was established in 1989 by GSA and AASG. It recognizes work on environmental geology issues such as water resources, engineering geology, and hazards.

John C. Frye joined the US Geological Survey in 1938, he went to the Kansas Geological Survey in 1942, he was its Director from 1945 to 1954, he was Chief of the Illinois State Geological Survey until 1974, and was Geological Society of America Executive Director until his retirement in 1982, shortly before his death. John was active in Association of American State Geologists and on national committees, and was influential in the growth of environmental geology.

The Award is given each year to a nominated environmental geology publication published in the current year or one of the three preceding calendar years either by GSA or by a state geological survey. A shared $1000 prize and a certificate to each author is presented at the AASG Mid-Year meeting, held Tuesday morning at the GSA annual meeting.


Citation: White, Jonathan L., Matthew L. Morgan, and Karen A. Berry. Bulletin 55 – The West Salt Creek Landslide: A Catastrophic Rockslide and Rock/Debris Avalanche in Mesa County. Bulletins. Golden, CO: Colorado Geological Survey, 2015. Bulletin 55.
May 152017
 

Can you name the features of the endless Rocky Mountain skyline as seen from the Front Range? Where are they actually located? The OF-16-03 Colorado Rocky Mountain Front Profiles poster is the key to finding out. Similar profiles created in the past featured approximate or artistic interpretations of the many summits. This poster accurately locates the elevation points as they exist in geographic space.

The CGS is proud to present this unique perspective of the dramatic Front Range of Colorado as a large 54×28 in (137×71 cm) poster offset-printed on premium glossy stock. The author and designer of this special edition poster, Larry Scott, is a long-time member of the CGS staff. A talented illustrator, he handles the design work on our maps, books, pamphlets, posters, and other print material. This special project is the realization of his long-standing interest in Colorado topography.

The elevation profiles are drafted horizon lines of the heights of the Continental Divide eastward towards the High Plains. Each mesa, hogback, hill, mountain top, and points in between were plotted by intersecting its specific elevation with its latitude. The relative viewing elevation is about 9,500 ft (2900 m), the halfway point of the vertical scale. This allows one to see what cannot typically be seen from ground-level along the Front Range. If you’ve ever flown into/out of Denver International Airport — altitude 5430 ft (1655 m) — and are sitting on the west side of the plane, this is what you might see a few minutes after taking off or before landing. From this vantage, many of the great mountain ranges of central Colorado to come into view; the Sangre de Cristo, the Sawatch, the Mosquito, and others up to and occasionally beyond the Continental Divide.

Below the three profiles are 32 selected highlights of notable geographic, historic, and geologic locations as indicated via numbered circles. Many of these cite special locations for viewing the various peaks and summits. For example, on a clear day in Denver — something that happens around 300+ days a year — a perfect place to see the mountain horizon is from City Park on the west steps of the Museum of Nature and Science. At an elevation of 5,500 ft (1675 m), this panoramic vista includes much of the Front Range with the downtown Denver skyline in the foreground.


From the Explanation:

Each profile is a one-degree section beginning in the south at 37° 42′, the central section at 38° 42’, and the northern section at 39° 42’. As the south-north extent of Colorado lies between 37° and 41° latitude, these profiles represent three-quarters of the Colorado Rocky Mountain Front Range. This refers the region of mountains that descend to the plains from the Pikes Peak massif in the south, north to the Wyoming border and inclusive of all summits east to the Continental Divide. South of Pikes Peak, the mountains begin to trend southwesterly all the way to Cañon City where the Arkansas River cuts through the Royal Gorge and flows out onto the piedmont. South of Cañon City, the Wet Mountains form a barrier that drops to the plains along Interstate-25 (I-25). Further south, though not shown, the mountains lay more to the west in a broad stretch, dramatically reappearing in the form of the Spanish Peaks, which extend eastward from the spine of the southernmost Sangre de Cristo Mountains in Colorado, the Culebra Range. To the north, beyond Rocky Mountain National Park, the mountains descend steadily to the Cache la Poudre River, marking the terminus of the Northern Section.

An excerpt:

Clear Creek Canyon — Long before there was an I-70 to access the high country there were only Native American foot trails along Clear Creek. In 1858, after trace amounts of gold were discovered in Cherry Creek south of Denver, gold seekers soon began looking in the mountains. Early in January 1859, George Jackson found gold at “Jacksons Bar”, where Chicago Creek joins Clear Creek in present-day Idaho Springs. The “gold rush” was on and the canyon became the gateway to the mining camps, most notably those in the Central City area via North Clear Creek. The Colorado Central Railroad (1871-1939) occupied the canyon in those days, later becoming the roadbed for US-6. The road was not completed in the canyon until 1952 due to political infighting and the time needed to complete six tunnels in the narrow spots. Rockfall remains a constant threat along the Canyon, with a notably large event closing the road in the summer of 2005 for almost three months—the longest full-road closure in state history.


Citation: Scott, Lawrence. OF-16-03 Colorado Rocky Mountain Front Profiles. Profile. Open File Report. Golden, CO: Colorado Geological Survey, May 2017.
May 132017
 

We’ve decided to revive one of our most popular print publications — RockTalk — as a blog so that we can continue to bring you interesting, informative, and timely postings related to our mission. This year, 2017, will see 110 years since the founding of the CGS.

The first RockTalk appeared in 1998 and was followed by forty seasonal issues until the most recent one in 2011. We constantly get requests for back issues and to continue publishing, so in accordance with the times, we decided to make the shift to digital media. We hope you will join us by subscribing (to receive an email when we make a new posting, please enter your email in the subscription box in the right-hand column).

Content-wise, we’ll be exploring all of the many aspects of our State Survey mission to:

  • Help reduce the impact of geologic hazards on the citizens of Colorado
  • Promote responsible economic development of mineral and energy resources
  • Provide geologic insight into water resources
  • Provide geologic advice and information to a variety of constituencies

And, along the way, we’ll also post pertinent information on general geology, geoscience research and education, science and engineering policy, and other items that cross our screens. If you have any questions or suggestions, please get in touch!

May 032017
 

The CGS recently installed the first of five new seismic recording stations that will collect information on seismic events around the state and the region. The CGS seismic network acts in conjunction with those maintained by the University of Colorado and Colorado State University, the Incorporated Research Institutions for Seismology (IRIS), and the US Geological Survey‘s National Earthquake Information Center (NEIC) — to provide near real-time earthquake detection. The addition of our monitoring capacity, the wider network allows the geoscience research community to better understand background seismicity in Colorado and better discriminate between natural and induced seismic events that may occur in the region.

The CGS already operates four other stations with Streckeisen STS-2 Broadband Sensors (capable of sensing ground motions over the frequency band 0.01 Hz (100 sec) to 15 Hz). They were part of a national consortium — USARRAY — that was a portable seismic network migrating around to different locations in the US several years ago. State-level organizations were allowed to ‘adopt’ some of the stations that were deployed within each state. The CGS purchased the four stations in 2010 — they are included on the map below as red boxes.

The set-up for a typical recording station includes the seismometer and its associated data recorder, a power system, and a communications system. The install site is carefully chosen for its relative acoustic silence — such that human-caused (road and air-traffic) and natural (wind, animal) noise levels are minimal at the relevant frequencies. The CGS cooperates with the Colorado State Land Board and the Colorado State Parks system in locating optimal sites for the stations in the CGS network. The particular station illustrated here is our Briggsdale Seismic Station #T25A-1 near Greeley, Colorado.

The physical installation of an isolated off-grid seismometer station includes the excavation of a pit for the seismometer ‘vault’ to sit in, a trench for cabling from the seismometer to the recording and power equipment, and a photo-voltaic (solar) power and data transmission tower. Adequate fencing to isolate the installation from noise and physical disturbance — in this particular case, grazing cattle — is important.

Images from the installation of our fifth seismometer station near Briggsdale, Colorado.

A seismometer is a device that can sense a wide range of ground motions or vibrations. Environmental considerations require that its underground installation be both level and thermally insulated. A sub-surface concrete pad is prepared with a glass plate embedded on the top to provide a perfectly flat platform for the seismometer to sit on. After precise leveling, the seismometer is then connected to a data recording system that is installed some distance away in a weather-proof console — again to keep possible vibrations from the tower at a minimum. The data recording box includes an A-to-D (Analog-to-Digital) converter that digitizes the signal and prepares it for transmission via the communications system.

The communications system consists of a modem and a GPS transceiver. Once recorded by the seismometer, a seismic trace is converted to a digital signal, processed and sent via the modem to a local cell tower where it is relayed first to IRIS and then on to the NEIC for correlation and display. The GPS provides a standard clock signal for data synchronization, an important factor in coordinating each individual seismic station with the wider network of stations. The IRIS website provides current near-real-time data for the Briggsdale station as well as all other stations in the network.

The power system includes a deep-cycle marine battery, and a photovoltaic panel for recharging along with a voltage inverter/charge controller to ensure a stable power supply for the data recording and communications system.

The map includes our seismic stations (totaling five as of 2017) along with others available across Colorado:

Apr 122017
 

We just uploaded the most recent of our STATEMAP mapping products to our online store: the Geologic Map of the Longmont Quadrangle, Boulder and Weld Counties, Colorado. The STATEMAP series in general provides a detailed description of the geology, mineral and ground-water resource potential, and the geologic hazards of an area. This particular 7.5-minute, 1:24,000 quadrangle is located immediately east of the Front Range uplift of Colorado and includes most of the town of Longmont within its borders. The geologic map plates were created via traditional field mapping, structural measurements, photographs, and field notes acquired by the investigators. Richard F. Madole, Scientist Emeritus at the USGS was the lead geologist for the project. This free release from the CGS includes two plates (with a geologic map, cross-section with correlation, oblique 3D view, legend, and description) along with the corresponding GIS data package that allows for digital viewing, all in a single zip file.

From the map history:

The Longmont quadrangle is in the northern part of the Colorado Piedmont, which is a section of the Great Plains that is bounded on the west by the Front Range and on the east by the High Plains section of the Great Plains. It is distinguished primarily by the fact that it has been stripped of the Miocene fluvial rocks (Arikaree and Ogallala Formations) that cover most of the High Plains. Headward erosion of the South Platte and Arkansas Rivers and their tributaries caused most of the stripping. Like much of the Colorado Piedmont, the Longmont quadrangle is an area of low hills and plains underlain by Upper Cretaceous (100–66 Ma) sedimentary rocks. Most of these rocks consist of fine-grained sediment (clay, silt, and fine sand) that accumulated in a broad seaway (Western Interior Seaway). This seaway connected the areas of the present-day Arctic Ocean and the Gulf of Mexico and extended from Minnesota and western Iowa on the east to central Utah on the west.

Even before urbanization, Upper Cretaceous bedrock was exposed in only a few places in the Longmont quadrangle because loess of late Pleistocene age (126 ka to 11.7 ka) blankets about 85 percent of the area. Deposition of most loess is attributed to northwesterly winds, which during the last glaciation (between about 40 ka and 12 ka) were stronger than they are today, blowing across extensive areas upwind from the Longmont quadrangle that are underlain by siltstone, mudstone, and shale. Thus, eolian sediment covers almost all bedrock and surficial deposits (loose, uncemented sediment as opposed to rock) that were at the surface prior to the end of the last glaciation. The floors of the major streams in the Longmont quadrangle also bear the imprint of Pleistocene glaciations. The gravel deposits that are mined in several places along St. Vrain and Boulder Creeks consist mostly of granitic and gneissic rocks that were derived from the Front Range and transported to the piedmont during glaciation. The headwaters of the St. Vrain, Lefthand, and Boulder Creeks were glaciated repeatedly during Pleistocene time. The principal glaciers in these areas were 10–12 miles (16-20 km) long and as much as 600–1150 ft (2-350 m) thick.

This mapping project was funded jointly by the U.S. Geological Survey through the STATEMAP component of the National Cooperative Geologic Mapping Program, which is authorized by the National Geologic Mapping Act of 1997, and also by the CGS using the Colorado Department of Natural Resources Severance Tax Operational Funds. The CGS matching funds come from the severance paid on the production of natural gas, oil, coal, and metals. Geologic maps produced through the STATEMAP program are intended as multi-purpose maps useful for land-use planning, geotechnical engineering, geologic-hazard assessment, mineral-resource development, and ground-water exploration.

Citation: Madole, Richard F. Geologic Map of the Longmont Quadrangle, Boulder and Weld Counties, Colorado. Geology. Open File Reports. Golden, CO: Colorado Geological Survey, April 2017.
Mar 142017
 

We just found out about this year’s Cumbres & Toltec Geology Train adventure in southwest Colorado/northwest New Mexico — 18 June 2017. It’s a special opportunity to enjoy some of that Rio Grande Rift, Brazos Uplift, Tusas Mountains, San Luis Basin, and San Juan Sag scenery.

Our very own Peter Barkmann, geologist extraordinaire and veteran Geology Train guide, will be on board for an informative and energized day in the high country.

On June 18th, a special train will depart to traverse spectacular geology along the 64 miles of Cumbres & Toltec track. But simply experiencing the incredible overviews of the Rio Grande Rift, the eruptive evidence of the San Juan Volcanic field, the Precambrian core of the Tusas Mountains, recent glacial deposits, and snapshots of the Jurassic, will not be enough. This special train will stop at many outcrops and rail cuts along the right of way, to mingle, marvel and collect photographs, samples and experiences only accessible on the train route.

ALL ABOARD!

Feb 282017
 

We have a free 8.5- x 11-inch (pdf) geologic map of Colorado containing Geo-Whizology of Colorado on the reverse side.

Free 8.5- x 11-inch  map of Colorado geology along with Geo-Whizology

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

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 most diverse:

For instance, did you know: Continue reading »

Feb 282017
 

No Geologist worth anything is permanently bound to a desk or laboratory, but the charming notion that true science can only be based on unbiased observation of nature in the raw is mythology. Creative work, in geology and anywhere else, is interaction and synthesis: half-baked ideas from a bar room, rocks in the field, chains of thought from lonely walks, numbers squeezed from rocks in a laboratory, numbers from a calculator riveted to a desk, fancy equipment usually malfunctioning on expensive ships, cheap equipment in the human cranium, arguments before a road cut.

— Stephen Gould

Any other ideas as to where/how creative geologic ideas arrive? Any personal mythologies out there?

Feb 242017
 

One of the many fascinating videos from our geo-friends up the road at University of Colorado-Boulder.

The Interactive Geology Project was formed in 2002 by professor Paul Weimer and colleagues with the goal of producing short 3D animations about the geologic evolution of key US national parks. The first major project focused on the geology of the Colorado National Monument and is still on display in the park’s visitor center. Over time our focus shifted from national parks to animating Colorado’s geologic history, with a key goal of developing a series of 5-10 minute vignettes covering each geologic time period.

The current group of animators joined the project in the summer of 2011. In 2013 we began a major collaboration with the Denver Museum of Nature and Science to explore new ways of using 3D technology in earth science education. We work with top subject-area experts to ensure our animations are as scientifically accurate and up-to-date as possible.

Our projects are on display in museums, parks, and other venues across Colorado, the Western US, and Canada. All of our work is also available to the general public free of charge on our website and our Vimeo page.

Feb 192017
 

Diamonds are formed from pure carbon, one of the most abundant elements on planet Earth. Diamonds, even from ancient times, have been sought for their extraordinary hardness (they are the hardest substance known) and their brilliance, especially in the colorless transparent gemstone variety. Ironically the other form of pure carbon is graphite, which is very soft with a soapy feel and a dull gray color. Graphite is commonly the “lead” in a pencil.

A diamond's crystal structure: tetrahedrally bonded carbon atoms crystallized into the diamond lattice, a variation of the face-centered cubic structure.

A diamond's crystal structure: tetrahedrally bonded carbon atoms crystallized into the diamond lattice, a variation of the face-centered cubic structure.

The Mohs Hardness Scale of minerals starts at 1 (talc) and ranges to 10 (diamond). That does not mean that diamonds are ten times harder than talc; mineral number 9 on the Mohs scale is corundum, a class of minerals which includes rubies and sapphires. Diamonds can be from ten to hundreds times harder than corundum. Diamonds themselves vary in hardness; for example, stones from Australia are harder than those found in South Africa.

The four main optical characteristics of diamonds are transparency, luster, dispersion of light, and color. In its pure carbon form, diamond is completely clear and transparent. As in all natural substances, perfection is nearly impossible to find. Inclusions of other minerals and elements cause varying degrees of opacity. The surface of a diamond can be clouded by natural processes, such as the constant tumbling and scraping in the bed of a river.

Luster is the general appearance of a crystal surface in reflected light. Luster of a smooth crystal face of diamond is strong and brilliant. It is intermediate between glass and metal and has its own special term — adamantine.

Relative size of octahedral diamond crystals from 1 to 500 carats. Credit: Modified from Bauer, 1968.

Relative size of octahedral diamond crystals from 1 to 500 carats. Credit: Modified from Bauer, 1968.

The process of white light breaking up into its constituent colors is called dispersion. Diamonds have strong dispersion, which along with their strong luster, causes the beautiful play of colors so often referred to as the “fire” of a diamond.

Gemstone varieties of diamond and imperfections. Yellow or yellowish-brown and even brilliant yellow diamonds have been found. Very rarely, diamonds are blue, black, pale green, pink, violet, and even reddish.

The most famous blue diamond, the Hope Diamond, is intertwined with Colorado’s mining history. Thomas Walsh, discoverer of the rich Camp Bird Mine near Ouray, purchased the Hope Diamond for his wife in the early 1900s; it was later given to his daughter, Evelyn Walsh McLean who wore it almost continuously until the 1940s. The 45.5-carat Hope Diamond now resides at the National Museum of Natural History in Washington, D.C.

Diamonds, in their perfect cubic crystal form, occur as isolated octahedral (eight-sided) crystals. Many variations on the cubic form are found in are usually clear and colorless, often containing minor inclusions nature, including twelve-sided crystals and a flattened triangular shape known as a macle. Gemologists recognize three main varieties of diamonds: ordinary, bort, and carbonado. Ordinary diamonds occur as crystals often with rounded faces, from colorless and free from flaws (“the first water” [1]) to stones of variable color and full of flaws. Bort diamonds occur in rounded forms without a good crystal structure. They are generally of inferior quality as a gemstone. Carbonados are black opaque diamonds usually from the Bahia Province of Brazil. They are crystalline but do not possess the mineral cleavage found in ordinary diamonds.

[1] An expression which refers to the highest quality diamonds and has come to mean the highest quality of just about anything. The comparison of diamonds with water dates back to at least the early 17th century, and Shakespeare alludes to it in Pericles, 1607:

Heavenly jewels which Pericles hath lost, Begin to part their fringes of bright gold.
The diamonds of a most praisèd water Doth appear, to make the world twice rich.

Diamonds in the rough, note the regular octahedral forms and trigons (of positive and negative relief) formed by natural chemical etching.

Diamonds in the rough, note the regular octahedral forms and trigons (of positive and negative relief) formed by natural chemical etching.

Feb 172017
 
IS-79 Colorado Mineral and Energy Industry Activities 2015-16 (cover)

The current annual Colorado Mineral and Energy Industry Activities report 2015-16 is now available. Following up on the 2014 report, this report, based on 2015 production data, sketches a comprehensive overview of Colorado’s mineral resource production. Of note is the fact that total value of mineral and energy fuels production in Colorado for 2015 is estimated to be $13.43 billion, a 29% decline from the $18.8 billion production value in 2014. The decline was caused primarily by a precipitous decrease in oil and gas market prices which provide 70% of Colorado mineral resource revenue. Oil and gas production actually registered at all-time highs of 127.6 Mbbl and 1,709 Bcf, respectively.

Nonfuel mineral production — including metals, industrial minerals, and construction materials — posted a modest 3.9% increase in revenue. Increased production of crushed stone, cement, and sand and gravel aggregate accounted for the increase. With a 2015 production of 21,790 metric tons of molybdenum from two mines, Colorado is the largest molybdenum producer in the U.S. Although just one mine in the state publicly reported gold production in 2015, Colorado remains the third largest producer of the metal in the U.S. as it was in 2014.


Citation: Cappa, James A., Michael K. O’Keefe, James R. Guilinger, and Karen A. Berry. “IS-79 Colorado Mineral and Energy Industry Activities 2015-16.” Mineral and Energy Industry. Information Series. Golden, CO: Colorado Geological Survey, 2016.
Feb 172017
 

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.

(00:36:32, stereo audio, 70.1 mb)

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.

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.

Feb 142017
 

Uranium is a widespread and ubiquitous element. It has a crustal abundance of 2.8 parts per million, slightly more than tin. Primary deposits of uranium tend to concentrate in granitic or alkalic volcanic rocks, hydrothermal veins, marine black shales, and early Precambrian age placer deposits. Secondary (or epigenetic) deposits of uranium are formed later than the surrounding rocks that host the mineral deposit. Uranium is soluble in oxidizing aqueous solutions, especially the U+6 valence state, and can be redistributed from primary source rocks into porous sedimentary rocks and structures by groundwater and form secondary (epigenetic) uranium mineral deposits.

Epigenetic deposits of uranium in sedimentary rocks form the bulk of uranium deposits in Colorado. These include the many mines of the Uravan, Cochetopa, Maybe, and Rifle districts, and other scattered places including the Front Range and Denver Basin. Primary uranium deposits in Colorado occur in hydrothermal veins, especially in the Front Range. Continue reading »