Castleguard Cave

Castleguard Cave is closed

Castleguard Cave is closed to the general public under Section 8 of the National Park General Regulations. Unauthorized attempts to enter Castleguard Cave, or any cave in a national park could result in arrest and/or charges under the Canada National Parks Act.

As Canada's most internationally-recognized cave, Castleguard Cave is a very special part of Banff National Park.

Located in the north end of the park, this limestone cave was formed by glacial drainage from the Columbia Icefield. It was first mentioned in the historical record over 100 years ago, though likely known to Indigenous peoples prior.

Since the first formal expedition to Castleguard Cave in 1967, speleologists from all over the globe have come to Banff National Park to conduct research in the cave and improve our understanding of this key biodiversity area.

On this page

• About the cave
• History
• Ecological significance
• Geological significance
• Cave access

About the cave

Castleguard Cave is one of Canada’s most storied caves within the caving community — for good reason. As the only currently known subglacial cave in the world, Castleguard Cave contains some features and lifeforms found nowhere else on Earth. Some research suggest the cave was formed as early as 1.25 million years ago.

Featuring over 21.3 km of surveyed passages, it is Canada's longest known single-entrance cave system and “ice plugs” can be found at its end points or "termini". In summer, Castleguard Cave experiences seasonal flooding of glacial meltwater from the Columbia Icefields. In winter, remaining meltwater will freeze solid near the entrance and remain liquid inside the cave including the “sump”, a submerged passage in Castleguard Cave.

Aside from the light which penetrates 200 m into the cave from its entrance, all the surveyed passages of Castleguard Cave exist in complete darkness. There is only one known entrance to Castleguard Cave as the Columbia Icefield covers all other potential openings.

“In a very real sense, the caves are more remote and much less easily explored than our most northernly Arctic islands”

Castleguard Cave was designated a Key Biodiversity Area in 2023 and was one of the first sites in Alberta to receive this globally significant designation. The cave is extremely important habitat for an organism found nowhere else on Earth — Castleguard Cave Stygobromid or Amphipod (Stygobromus canadensis). The designation does not provide any additional legal protections but increases awareness and visibility for this very special ecosystem. Castleguard Cave is located in “Zone I - Special Preservation” within Banff National Park and receives the highest level of protection under the Canada National Parks Act.

  Click to enlarge

History

Many Indigenous groups, such as the Ktunaxa, Iyarhe Nakoda, and Niitisitapi (Blackfoot) frequented the mountain passes around the Castleguard area, and there were likely many visitors to the cave before it entered the written record in the twentieth century.

“The first thing I knew I came round the corner and here was this big cave in front of me … ”

The first recorded mention of Castleguard Cave refers to a 1921 trip when outfitter Cecil Smith came across the cave entrance one morning while rounding up his horses. Smith was hired to guide American paleontologist and secretary of the Smithsonian Institution Charles Walcott and his wife, Mary Vaux Walcott, through various areas of Banff National Park in the summer of 1921. Walcott requested Smith guide him to the Columbia Icefield, though Smith had never visited the area himself. Smith and the Walcotts explored the cave by matchlight and spent time around the entrance admiring its seasonal flooding.

In the years that followed, other groups would attempt to explore Castleguard Cave. These bold explorations were not without risk – seasonal flooding, entrapment, and death were all real possibilities for those who dared to take part. Apparently Ulysse La Casse, who visited the Castleguard area on the 1923 and 1924 exploratory trips, fell into a glacial crevasse both times.

The first formal expedition to Castleguard Cave took place in 1967 by members of the Karst Research Group with McMaster University in Hamilton, Ontario. Since then, under permits from Parks Canada, various speleologists, cavers and researchers from around the world with defined scientific objectives have carried out expeditions to Castleguard Cave.

The 1967 expedition directed by Canadian speleologist, Derek Ford, led to new species later being identified in 1980 by Dr. John Holsinger, a well-known American cave biologist known as “Captain Karst”.

Ecological significance

Formal exploration of Castleguard Cave only began in the mid-20^th century. As exploratory expeditions picked up in the 1970s and ‘80s, researchers reported tiny white invertebrates crawling around in streams and pools.

These invertebrates exist in 2°C glacial meltwater, in a nutrient-poor environment with no light. They are pigmentless creatures the size of an uncooked grain of rice. Their food sources, reproduction cycles, and lifespans are unknown. Although rare and mysterious, these tiny organisms are important for what they can tell us about life on earth before the last ice age.

Two unique species of invertebrate have been identified in Castleguard Cave:

Stygobromus canadensis appears to have survived the glaciation of the surrounding landscape during the last ice age which began 100,000 to 75,000 years ago and ended about 11,000 years ago (Wisconsinan glaciation). In fact, scientists studying cave features called speleothems, including stalagmites and stalactites, can tell that the cave’s interior has remained intact and ice-free for at least 700,000 years. That’s almost half a million years longer than the first known evidence of human beings (Homo sapiens) on Earth.

“It’s about what the species can tell us about life before the last ice age ... this species survived inside the cave, while the outside environment was scoured by glaciers during the last ice age”

In 2007, 40 Stygobromus canadensis were counted and, in 2021, only 8 were counted. However, looking for invertebrates this small in over in 21 kilometres of cold, poorly lit passages is challenging and more research is needed before conclusions can be drawn from these numbers.

Castleguard Cave’s very long and stable geological history may have allowed the creatures living inside it to evolve into unique species, adapt differently than related species outside the cave, or both. The invertebrates may even be remnants of very old pre-glacial population distributions that survived only because the cave provided a refuge under the ice.

Key biodiversity area designation

In 2023, Wildlife Conservation Society Canada designated Castleguard Cave as a key biodiversity area (KBA) because of the rare invertebrate species found within it, some nowhere else on Earth.

Although this KBA designation does not provide any additional legal protections to Castleguard Cave, it helps increases awareness and visibility for this very special ecosystem and the rare species found within it. The designation can also help ensure that greater attention is paid to this unique underworld that may see more flooding from glacial meltwaters due to climate change or other changes.

Geological significance

Castleguard Cave is the only known cave in the world found under a glacier or an icefield. Many explored passages of Castleguard Cave terminate with "ice plugs", which are believed to be formed by the glacier pushing down into the cave from above. These frozen features have changed very little over the course of formal expeditions spanning nearly 60 years. The images below show the same ice plug 9 years apart with a 1-2 cm difference, highlighting the relative stability of this environment. However, recent monitoring of ice levels at the entrance and the movement of large quantities of rock in the cave may indicate climate change. This could mean faster melting glaciers, shifting groundwater, and the possible loss of these water sources in the future.

The subglacial nature of this cave provides a unique opportunity for researchers to understand this landscape and how it has evolved over time. Most extraordinarily, the landscape inside Castleguard Cave has remained stable for at least 700,000 years. In comparison, the landscape on the surface was scoured by glaciers during the last ice age and is “nearly new” at 10,000 years old.

“It’s a special cave with a pretty ancient landscape”

Not only does Castleguard Cave have significant ecological importance as a Key Biodiversity Area, but it also includes one of only five known examples in the world of highly unusual, nearly cubical “cave pearls.”

Within Castleguard Cave, a notable variety of other special features exist including stalagmites and stalactites, precipitates of gypsum, hydromagnesite and rare cave minerals. Outside the cave, the Castleguard area also contains significant karst features.

Castleguard Cave and the surrounding area including Castleguard Meadows exist in a special preservation zone of Banff National Park (Zone 1). The alpine meadows around the cave are considered an outstanding example of pristine alpine vegetation.

Cave access

Castleguard Cave is an ancient, fragile environment with unique features and species found in few other places or nowhere else on earth. Portions of the cave are submerged for much of the year making travel technical and intense.

Castleguard Cave is located in Zone 1, a special preservation zone in Banff National Park, which is the highest level of protection in national parks. Access to Castleguard Cave has been restricted by Parks Canada since the early 1970s. The entrance has a locked gate – entry requires permission, and a special permit issued by the Field Unit Superintendent.

Located deep in the backcountry of Banff National Park, reaching the cave and travelling through it is a multi-sport endeavour. The cave is only accessible during the winter because melting snow and glaciers cause frequent and unpredictable flooding. Access requires a 20-kilometre ski over gravel flats, a glacier, glacial moraines and alpine meadows. Trail breaking in deep snow, high winds and white-out conditions can make getting to Castleguard Cave very difficult.

The role of researchers, conservationists, and speleologists

Castleguard Cave remains one of the most special parts of Banff National Park. Our understanding of this remarkable underground environment and ecosystem is still evolving and growing with each visit.

“Castleguard captures the imagination. Cave passages that were carved by unbelievable volumes of water, then dry periods when stalagmites form, then a wet period where formations are dissolved, followed by more growth. There are red squirrel bones from when a forest was atop Mt Columbia; and that evidence has been trapped inside a cave, under 300m of ice for at least 8,000 years.”

Parks Canada appreciates the perseverance and hard work of all speleologists, researchers, and conservation-enthusiasts over the years who have dedicated their time to increasing scientific knowledge of this special place. Many are members of the Alberta Speleological Society and have made significant contributions to better understand Castleguard Cave.

Parks Canada would also like to thank the Wildlife Conservation Society Canada and the Key Biodiversity Areas organizations for their efforts to build recognition for Castleguard Cave as a key biodiversity area.