Castleguard Cave

Castleguard Cave is a limestone cave located at the north end of Banff National Park in the Rocky Mountains of Alberta, Canada. With 20,357m of surveyed passages (as of 2007), it is Canada's longest cave, and its fifth deepest at 384m. Castleguard Cave ascends gently from its entrance and terminates beneath the Columbia Icefield.

Castleguard Cave is modest in size compared to other great caves of the world, but nevertheless is well known amongst cavers and speleologists internationally. It is the subject of a film and a coffee-table book, and is mentioned in most cave reference books in print.

This attention is due in part to its magnificent, remote mountain setting. Its location within a protected area in a national park prohibits motorized ground access, and the risk of flooding in its entrance has limited most explorations to mid or late winter, so cavers must access it via a 20 km (12 mi) ski with towed sleds, or by helicopter. This feeling of remoteness is compounded by the cave's linear layout and its single entrance. The classic trip, from the entrance to the Ice Plug by the shortest route, traverses 9 km (6 mi) of cave passage. Cavers often are underground for four or five days, staying at two underground camps.

Most northern caves are not well decorated with cave formations, but Castleguard Cave has some sections with good flowstone and stalactites, and is known for its nest of exceedingly rare cubic cave pearls and extensive displays of flagged soda straws. The back passages of Castleguard Cave are the only ones in the world that end in plugs of glacial ice pushed into the cave from the sole of a surface icefield.

It has been suggested that the cave was a refuge for the isopods and other life found in its pools during periods of glaciation. One unique species, the amphipod Stygobromus canadensis, was identified in 1977.

Castleguard Cave lies within the Cathedral Formation limestone, except the headward complex which is in the overlying Stephen Formation shaley limestones. Their gently-dipping bedding (about 5 degrees) is reflected in the near-horizontal aspect of the cave. Although the entrance and headwater sections are more complex, the central portion of the cave consists of a single main passage alternating between long sections of vadose (rift or canyon) passages linked by shorter phreatic (tubular) sections. Much of the cave is dry, excepting the entrance series which floods unpredictably in summer.

...
Wikipedia