The glacial history of the Mission Valley is a big part of what makes this a great retriever training area.
Many years ago during the geologic time period called the Pleistocene much of Canada and northern United States were covered with large continental glaciers. In this area this ice sheet extended nearly as far as St. Ignatius at the south end of the Mission Valley. Slightly more recently it extended only to Polson.
As the ice sheet melted, the meltwater carried fine sediment which has filled the Mission Valley with about 400 feet of sediment. These fine clay particles are what enable the “glacial pot holes” that are common in the area - especially in the St. Ignatius/Charlo area - to hold water. These potholes that hold water so well provide wonderful waterfowl habitat. The glacial silt with its excellent water-retention properties also means that retriever training ponds dug throughout the Mission Valley tend to hold water well. The glacial deposits also provide the landscape which varies from gently rolling to very hilly because the terrain has mostly been formed by glacial processes rather than by running water/streams.
So, if you like waterfowl hunting and dog training in this area – Thank a Glacier!
A couple more interesting facts from the glacial lore of this area:
Just before you drive into Polson from the trial grounds you drop down what is locally known as Polson Hill. This feature is actually a “terminal moraine," essentially the end location of a great ice sheet which, as it melted, deposited rocky debris at its terminus, leaving us with Polson Hill.
A notable feature on the open hillsides to the west and within the Mission Valley are the distinct parallel lines on the hills. These are the markers of ancient shorelines formed when the enormous Glacial Lake Missoula occupied this valley and other valleys throughout much of western Montana.
