Limitations:

This landslide inventory only reflects the location of landslides digitized from existing maps prepared by many different authors. No original landslide mapping was completed for this inventory. This inventory also does not presently include landslides mapped by private consultants, or academic or professional publications outside of the CGS and USGS. The lack of a mapped landslide in a given area does not imply that landslide do not exist at or near that location, or the ground is inherently stable. This map viewer should be used by trained individuals using it in conjunction with geologic bedrock maps, an understanding of the shear strength of geologic formations, hydrologic conditions, and steepness of slope to recognize regional susceptibilities of slope instability. It should not be utilized in-lieu of site-specific investigations to identify the threat of landsliding, or slope-stability adequacy for a specific land usage.

 

The CGS is digitizing all mapped landslides that have been published in geologic and geologic hazard maps of Colorado. Landslides have been digitized as map polygons from four broad categories of geologic maps.

·        The yellow polygons are landslides digitized from all published 1:24,000-scale (1 inch equals 2,000 feet) maps by CGS and USGS. These maps include standard geologic maps of 1:24,000-scale quadrangles and specific geologic hazard mapping that has been completed at the 1:24,000 scale in several areas of the state. This map scale, where features are larger, will have the best detail. The boundaries of the mapped 1:24,000-scale quadrangles are also shown in the map viewer.

·        The olive-green polygons are landslide polygons digitized from smaller map scale 1:48,000 to 1:100,000 geologic maps. This collection of maps is only partially represented in the inventory at this time.

·        The red polygons are landslide areas digitized from 1:250,000-scale USGS mapping in the mid 1970s by Colton and others on 1 degree by 2 degree quadrangles.

·        The orange polygons are landslide and unstable slope areas digitized from all available geologic hazards mapping that was completed in the mid 1970s under the auspices of Colorado House Bill 1041. Most of this work was completed in a 1:24,000 scale.

In the Colorado landslide inventory map viewer, each polygon that represents a mapped landslide can be queried for the publication citation and the map unit. More than one scale of map exists in many areas of the state. In those areas, there are overlapping landslide polygons.

Map Guide:

The ArcGIS-based map is zoomable and layers can be turned on and off to view the various data layers. General instructions/helpful hints for navigating in the map hosted in ArcGIS.com are as follows:

 

*The “i” in the top right of the screen gives information about the Map

 

*The next button to the right with the 3 horizontal lines is the Legend of the currently displayed layers

 

*The next button to the right is the Layers button where you can turn Layers on and off.  Click each little triangle next to the Layers to further drill down the list.

 

*The next button with four squares next to one another is the Basemap list, you can click this button to change to Imagery if desired.

 

*The next button to the right is the measure tool.  Use this tool when you would like to measure straight line distances between items on the map.

 

* One can zoom in or out using the + and – sign in the top left hand corner of the Geography box or by using a scrollable mouse wheel.

 

* Clicking the House button will take you back to the initial start state of the map.

 

Disclaimer:  These data are intended for use at 1:250,000 -  1:24,000 scale and are checked for accuracy accordingly. CGS does not assume responsibility for the use of these data and is not intended to be used past 1:24,000 scale.