This EarthCache will take you the parking area at the base of the steps to Ice Cave in Decorah, IA.
Ice Cave is the largest glaciere (ice cave) in North America east of the Black Hills. Ice usually appears in the cave in March, after the coldest days of winter are past. It reaches a maximum thickness of 8-10” on the walls in early June and does not disappear until August or September. This is in sharp contrast to other caves which maintain a constant temperature equal to the mean annual temperature of the region.
How does the ice form?
From 1897-1899 Alois Kovarik made frequent observations at the cave, collecting meteorological information and came to the following scientific conclusion still held valid today. Cold air circulates freely through the cave during the winter, cooling the rocks to a temperature below the freezing point of water. The warm air ascends out of the cave through fissures in the roof. Moisture in the air produces a coating of hoar frost in some locations, but production of thick layers of ice must wait for the arrival of water following a thawing of the bluff surface above. Since the mouth of the cave is higher than the ice chamber, cold air is trapped in the interior in summer. There is little circulation to bring heat in so ice is able to persist until August or September.
The Decorah’s Ice Cave sign near the parking area provides additional information which you should read to better understand this site and learn the history of this cave.
To receive credit for this EarthCache, you will need to e-mail the following answers:
- Take an outside air temperature reading before climbing the steps up to the cave. Enter the cave and when you come to a prominent Y (fork) in the trail take a second temperature reading. By crouching down at the Y (fork) in the trail you will be able to see the gated area or red keep out sign that is on the steeply descending trail to the right, so you will know you are in the correct area. You do not need to descend to the gated area itself.
- Fissures occur in the roof of this cave, allowing heat to escape and water to enter. If you are in here during daylight hours you will readily see light coming in through these openings. At what point in this cave do you see the largest fissures?
When logging this EarthCache, post a photograph of yourself and GPS or just your GPS at the cave entrance. Posting interesting photographs of this ice cave to educate other visitors to this EarthCache and to document your experience here are appreciated. .
WARNING: Caves can be dangerous. Enter at your own risk. You will need a flashlight. Ice may cover the floor during part of the season and rocks could dislodge. Access to the lowest part of the cave where the ice forms (ice chamber) has been gated off due to safety concerns.
Special thanks go to John Pearson, Botanist/Ecologist, Conservation & Recreation Division, Iowa Department of Natural Resources and to Rick Edwards, Director, Decorah Park-Recreation for granting permission to establish this EarthCache at Ice Cave.
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