Geologic Hazards in Wyoming January 2019 Summary Report

Wyoming State Geological Survey Geologic conditions that Erin A. Campbell, Director represent a risk to people, and State Geologist property, and infrastruc- ture are known as geolog- ic hazards. Because of the Laramie, Wyoming rural nature of Wyoming, phone: 307-766-2286 many geologic hazards oc- email: [email protected] cur without endangering website: www.wsgs.wyo.gov the public. However, when they occur near people or infrastructure—homes, buildings, roads, railways, and pipelines—they can cause injuries and dam- age. Geologists at the Wyo- Intrepreting the past, ming State Geological Sur- providing for the future vey (WSGS) study geologic hazards in an effort to mit- igate risk and protect the public. The WSGS is conducting Geologic hazards investigations related to in Wyoming: landslide susceptibility and occurrences, earth- • landslides quake activity, modern - • earthquakes logic deposits. The agency • expansive soils faults,also maintains and surficial databas geo- • windblown deposits es on earthquakes, land- • radon slides, and other geologic Northern Greys and Little Greys rivers corridors showing locations of • karst and sinkholes hazards that are available recent landslides at Squirrel and Porcupine creeks in Lincoln County, • volcanic eruptions to governmental agencies, Wyoming. land use planners, and the on April 17, 2018, when slope failure tem- public. The WSGS works with the Wyo- porarily dammed the Greys River and de- stroyed a portion of the Greys River Road in Lincoln County. It limited access to a large mingto study Office and of mitigateHomeland hazards Security within (WOHS) at- portion of the Wyoming range and affect- andrisk countycommunities. emergency mitigation officers ed tourism in Alpine, Wyoming. A smaller event occurred near Squirrel Creek that Landslides temporarily blocked the Little Greys River More information is Road, stranding a number of campers. By available at: Landslides are the downward movement gathering data, creating maps (see map of rock, soil, or earth caused by gravity, above), and providing input and geologic www.wsgs.wyo.gov/ and occur when a slope becomes unstable. hazards/hazards interpretation, the WSGS contributed to Although numerous landslides occurred a multi-agency group (including WOHS, in Wyoming during 2018, three notable Wyoming Department of Transportation, landslides are the Porcupine Creek, Squir- rel Creek, and Crandall landslides. - The Porcupine Creek landslide occurred Wyomingers) to assess Office and of respond Tourism, to the and events. Lincoln County officials and emergency manag The landslide in Park County near Crandall, Wyoming, Springs, Idaho, occurred in January 2018. It and many occurred in June 2018 (see photo at top of cover page). of its aftershocks were felt within the state, primarily in The slide encroached on a number of homes and cabins, Star Valley. Of the 36 earthquakes felt in Wyoming in the and destroyed two properties. The WSGS worked with past year, fewer than half had epicenters within the state. the WOHS in evaluating the surrounding areas to identify Modern faults, those that have ruptured in the last 1.6 landslide history and potential. million years, are considered potential earthquake sources. Wyoming hosts more than 30 of these modern Earthquakes faults (see map below). Studying these faults can provide Earthquakes occur nearly 2,558 earthquakes valuable information about previous earthquakes and every day in Wyoming (see occurred in and near clues to potential future events. The WSGS has recently map below), with the major- Wyoming from collaborated with geologists from the U.S. Geological Sur- ity occurring in the north- November 1, 2017, to vey, Bureau of Reclamation, and multiple universities to western corner, including October 31, 2018 study modern faults in Jackson Hole, the Washakie Basin, Yellowstone National Park. and near the Seminoe Mountains. Data gathered from In most cases, earthquakes go unnoticed due to their small magnitude. However, portions of the state. these projects are redefining seismic hazards for those when large enough, earthquakes that occur inside and The WSGS continues to be the primary state agency that outside of Wyoming can be felt in the state. For example, provides information related to all geologic hazards a magnitude 4.4 earthquake with an epicenter near Soda throughout Wyoming.

45°N M O N T A N A

Lovell Crandall Sheridan

M landslide o n t t a I a d n a a h o A Cody

T

Sundance O O

Buffalo

Gillette H K

A A

D D

44° N

I

Worland

H

Newcastle T

U

O

Dubois Thermopolis S Jackson

43°N S o u tt h D a k o tt a Riverton N e b rr a s k a Pinedale Soda Lander Casper Springs Afton Douglas Lusk Landslides at Porcupine and Squirrel creeks A

K

S

Torrington

I d A I d a h o 42°N U tt a h Wheatland R

B

Kemmerer Rawlins E

N

Rock Springs Green River Laramie Evanston Cheyenne

U T A H C O L O R A D O

Earthquakes, Nov. 1, 2017 through Oct. 31, 2018 City or town Felt earthquake 0 20 40 60 Miles Recent landslide Interstate highway Historic landslide County boundary 0 20 40 60 80 100 Kilometers Modern fault

Earthquakes in and near Wyoming from November 1, 2017, through October 31, 2018, as well as historic and recent landslides, and modern faults. Caption for cover photo: Oblique aerial photograph of a recent landslide near Crandall, Wyoming. (Photo provided by Park County)