Decorah Ice Cave


Useful Information

Location: Decorah Ice Cave State Preserve.
From Decorah cross the river on College Drive, then take the first right, Ice Cave Road. From the parking lot 400 m/5 minutes walk.
(43.312625, -91.781271)
Open: No restrictions.
[2021]
Fee: free.
[2021]
Classification: SpeleologyFracture Cave SpeleologyIce Cave
Light: bring torch
Dimension: L=45 m.
Guided tours: self guided
Photography: allowed
Accessibility: no
Bibliography: George E. Knudson, James Hedges (1973): Decorah Ice Cave State Preserve, Proceedings of the Iowa Academy of Science, 80(4), 178-181. online pdf
Alois F. Kovarik (1898): The Decorah Ice Cave And Its Explanation Scientific American Supplement, 46, (1195), Nov 26, pp 19158-9, cols 1-3;1-2 [Description; measurements of ice and temperature . See Anon, 1860(a) & (b)]
Address: Decorah Ice Cave, Ice Cave Rd, Decorah, IA 52101, Tel: +1-563-382-4158.
As far as we know this information was accurate when it was published (see years in brackets), but may have changed since then.
Please check rates and details directly with the companies in question if you need more recent info.

History

1860 cave first mentioned in the Scientific American.
1869 visited by State Geologist Charles A. White.
1929 opened as a show cave by Stanley Scarvie.
1941 show cave closed.
1954 cave gifted to the city of Decorah.
1973 declared a Geological State Preserve.
1978 placed on the National Register of Historical Places.

Description

Decorah Ice Cave is a cold trap, where cold air flows in during the winter, and stays inside during the summer. Cold air is denser and heavier than warm air, so cold air always flows downwards. The cave has the form of a pit with no lower exit, so the cold air is trapped. Ice build-up starts in the spring thaw when surface water seeps into the cave and is frozen by contact with the cold rock walls. The ice begins to accumulate in March, reaches a maximum thickness of 20 cm to 25 cm in June. The ice remains until August or September, depending on the summer temperatures. We recommend a visit between summer and early fall, when the ice in the cave is thickest. It is quite unimpressive if there is ice in the cave when there is ice all around, while it is quite impressive if there is natural ice inside while it is hot outside. The cave is open all year, but during winter the trails might be slippery.

The small park is located north of Upper Iowa River, opposite the city of Decorah. The cave was once a show cave, which actually does not require a lot of development. It is more a pit than an actual dark cave, and we guess there was not much development except trails, and of course an entrance fee. The cave was published in numerous scientific publications and this publicity was the reason why it became the first cave in Iowa to attract large numbers of tourists. Stanley Scarvie leased the site and built the trails and stairs which still exist. In the early years it attracted about 5,000 visitors per year. The enterprise was closed in 1941, due to World War II, and the cave was freely accessible afterwards. The cave is actually called Ice Cave, but this name is quite generic and there are numerous other Ice Caves, but with the addition of the name of the city it becomes unique.

Decorah Ice Cave is located beneath a south-facing bluff of Ordovician limestones of the Galena Group. The bluff is a result of the Iowa River eroding the plain. A vertical fracture through the limestone was enlarged by the downslope slipping of large blocks of rock on the shaly strata known as the Decorah formation. This is a form of tectonic cave which called a fracture cave. And there is a network of crevices which extend back into the uplands north of the bluff. Only some crevices are closed at the top.

Decorah Ice Cave is said to be the largest ice cave in eastern North America. This is based on the paper from 1973 we listed in the bibliography section above, but we are not sure if this is still the case. In this paper it is called a "glacière" which is a scientific term based on the French word for ice cave. As it is often wrongly cited without the accent, we suggest using the term "ice cave" instead, there is no glacier.

This is the U.S.A., so the most important sentence we read about the cave is “enter at your own risk” attraction. This is a park with trails, and obviously you are responsible for own your behaviour. We suggest good walking shoes, not just for the cave. There is a 400 m/5 minutes walk to the cave from the parking lot to the cave on a trail through the forest. The rear part of the cave was closed off with a barrier, since the DNR Geological Survey Bureau determined some rock movement in the late 90’s. As a result only the first 5 m of the cave are accessible.