Fourteen thousand years ago the spot where you are standing was covered by a massive sheet of ice a mile high. The fourth Wisconsin glacier carved a cluster of lakes into northwest Iowa. While this north-south cut is typical of glacial lakes, West Okoboji is unusual because it is so deep.
One theory is that a waterfall, coursing down the mile-thick ice, gouged the lake bed to it's depth of 136 feet or more. Or perhaps, the juggernaut of ice, shoving glacial rubble ahead of it, sculpted the 6 1/2 mile long basin, to be filled with melting ice as the glacier retreated.
Nine thousand years later there were forests here. Then the climate changed. Fires swept the forests, and prairie grasses, reeds, rushes, marshlands and fens took over.
Beneath the waters in front of you is a canyon of deep, dark, cool water. This "lake below the lake" touches the top waters, but does not intermingle. The top lake, because of a temperature inversion of heating and cooling, turns over twice a year.
West Okoboji is spring-fed, with an irregular shoreline of over 25 miles, all protected by filtering percolators in the form of wetlands. These natural factors, combined with several generations of dedicated environmentalists, have contributed to the enhanced quality of the brilliant blue water.
- To log a find for this EarthCache, complete the following and send your results to the cache owner through their profile page, using the "Send Message" link:
1. Use a thermometer (a common cooking/meat style works well), and record the lake temperature (you may skip this step during the winter months when the lake is frozen over). What is your measured temperature?
2. From information found on site, how much younger are the glacial deposits here compared to those at most other Iowa landscapes?
Photos are not a requirement for logging any EarthCache, but if you wish to include some they're appreciated.