During the last ice age, a large moraine was deposited in this
area effectively blocking the river Vinstra from draining to the
northeast. When the ice started to melt, the Vinstra river system
drained to the south through Espedalen and further down through
Gausdal. The result of which is the impressive potholes at Helvete
which can be seen if you descend into the canyon at the cache
"Visit Hell" (GCJTEN).
After some time (about 9.000 years ago) the water broke through
the moraine at Kamfoss. This caused Vinstra to drain to the
northeast again, carving out the Vinstra valley and the impressive
canyon you will see at the cache site.
Unfortunately the entire Vinstra river system was regulated for
hydro-electric power during the 1950s. At this time enviromental
issues were not given much attention, the result being a maximum
impact solution (max. power out, no protection of the environment).
Now the once mighty Vinstra river is completely dry for appx. 5 kms
below this point, and the water level of the dam above (Olstappen)
goes up and down according the the prices in the electricity
markets.
If you travel some 300 meters north down the road, you will see
the valley Jodalen on your left. This is the result of the large
flood called Stor-Ofsen from 1789. Before this a large farm was
situated here.
Do not enter the dry riverbed. The gates at the dam will
open without warning, and at any given time!