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The original item was published from 1/22/2021 12:06:45 PM to 3/22/2021 12:00:03 AM.

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City of Steamboat Springs NEWS

Posted on: January 25, 2021

[ARCHIVED] Sulphur Cave & Spring Designated National Natural Landmark

NNL Sulphur

STEAMBOAT SPRINGS, COLORADO-January 25, 2021-It might be out of sight to many, but the Sulphur Cave at Howelsen Hill is not out of the minds of natural resource experts and scientists across the county as evident by its recently prestigious designation as a National Natural Landmark (NNL) by the National Park Service.

“We’ve known that Howelsen Hill was special for its winter heritage, but now its unique geological features have emerged from the darkness of the underground cavern for the world to share,” said Parks & Recreation Director Angela Cosby.

Sites are designated as NNLs because they contain the best remaining examples of specific biological and/or geological features. The natural features represented include aquatic and terrestrial ecosystems, geological processes and resultant landforms, and records of geologic history. Each site is a piece of the larger picture that is the illustration of the great diversity of our nation's natural landscape.

An active hypogenic cave, this location sits at the base of the historic Howelsen Hill Ski Area on top of a travertine deposit that is probably no older than 126,000 years, making the cave the youngest solution cave in Colorado. However, the Sulphur Cave and Spring is a superb example of a cave that is actively undergoing sulfuric acid speloegensis – something extremely rare and the only known example in Colorado. 

The cave also contains many uncommon features including biovermiculations, gypsum crystals, native sulfur, snottites (a biologically formed speleothem) and the recently discovered blood-red worm (Limnodrilus Sulphurensis), which is unique to the cave and found nowhere else in the world. 

The Sulphur Cave and Spring was recommended to the National Park System Advisory Board for review this past year and subsequently approved this past week by the Secretary of the Interior for designation. Sites are recognized for their condition, illustrative character, rarity, diversity, and value to science and education. Steamboat Springs’ prized geological resource becomes the 601st National Natural Landmark site in the county. 

The National Natural Landmark program features 602 sites within 48 states, American Samoa, Guam, Puerto Rico, and the U.S. Virgin Islands. With the addition of the Sulphur Cave and Spring, there are now 15 sites in Colorado going back to the state’s first in 1965. Colorado landmarks range in size from a few acres to nearly 38,000-acres and include one of the best examples of Arctic tundra in the conterminous U.S., excellent examples of the titled and faulted sedimentary strata of the Colorado Front Range, and internationally known paleontological sites.


Angela Cosby, Parks & Recreation Director, 970.879.4300 or email
Brad Setter, Howelsen Hill Ski & Rodeo Manager, 970.879.4300 or email
Michael Lane, Communications Manager, 970.871.8220 or email

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