Slumgullion Earthflow

{{short description|Geographic feature in Colorado, USA}}

{{Use mdy dates|date=February 2025}}

{{Infobox Protected area

| name = Slumgullion Earthflow

| iucn_category =

| photo = Slumgullion Earthflow.jpg

| photo_caption =

| location = Hinsdale County, Colorado, United States

| nearest_city = Lake City, Colorado

| coordinates = {{coord|37.991665|N|107.25704|W|format=dms|display=inline,title}}

| area =

| established =

| governing_body =

| embedded1 = {{designation list | embed = yes

| designation1 = NNL

| designation1_date = 1983

}}

}}

File:Lake San Cristobal CO.jpg was created 700 years ago when the Slumgullion Earthflow created a natural dam.]]

The Slumgullion Earthflow is a remnant of a landslide in the San Juan Mountains in Hinsdale County, Colorado. It was designated a National Natural Landmark in 1983. It is also a Colorado Natural Area and an Area of Critical Environmental Concern.{{cite web |url=http://pubs.usgs.gov/bul/b2130/ |title=Bulletin 2130 -The Slumgullion Earth flow: A Large-Scale Natural Laboratory |publisher=US Department of Interior - US Geological Survey |date=March 23, 2012 |accessdate=July 5, 2013 |editor=D.J. Varnes and W.Z. Savage}}

The earthflow, a slow-moving landslide, crawled down the valley about 700 years ago creating the {{convert|4|mi|km|-long|sp=us|adj=mid}} and {{Convert|2000|ft|m|-wide|sp=us|adj=mid}} wide mass. The earthflow lies a few miles southeast of Lake City.{{cite web | url=http://www.blm.gov/co/st/en/BLM_Programs/areas_of_critical/visit_an_acec/acec_by_map/slumgullion_earthflow0.html | title=Slumgullion Earthflow | publisher=U.S. Department of the Interior - Bureau of Land Management | accessdate=July 5, 2013}} The landmark site covers {{convert|1291|acre|ha}} and is owned and managed by the US Forest Service and the Bureau of Land Management. It is "a striking example of mass wasting (the movement of large masses of earth material)." The Lake Fork of the Gunnison River was dammed by the earthflow, creating Lake San Cristobal.{{cite web|url=http://parks.state.co.us/NaturalResources/CNAP/NaturalAreasInfo/AlphabeticalListing/Pages/SlumgullionEarthflow.aspx |title=Slumgullion Earthflow |publisher=Colorado Parks and Wildlife |accessdate=July 5, 2013 |url-status=dead|archiveurl=https://web.archive.org/web/20120827102857/http://www.parks.state.co.us/NaturalResources/CNAP/NaturalAreasInfo/AlphabeticalListing/Pages/SlumgullionEarthflow.aspx |archivedate=August 27, 2012 }} A second earthflow has been moving continuously for about 300 years over older, stable rock. It moves at a rate of about {{Convert|7|m|ft|sp=us}} per year.{{cite web |last=Hagenauer |first=Beth |title=NASA Conducts Airborne Study of Colorado Landslide |url=http://www.nasa.gov/topics/earth/features/slumgullion.html |publisher=NASA Dryden Flight Research Center |accessdate=May 9, 2014 |date=October 8, 2012}}

The area is a habitat for elk and deer. It is crossed by Colorado Highway 149, the principal highway of the area connecting Lake City with Creede.