In the past I've read that airplanes flying thru the cloud layer are a common cause. I like simple explanations.
Here's a link that has other theories and more detail.
Nice one, Elmo.
Fantastic. Just found this place today, the history you've provided makes it even more special.
Very Beautiful Picture!!!
A HIGHLY FAVORITE AND LIKE PICTURE!!!
Carved by Peter Wolf Toth, finished in Feb 1977. He made one for each of the 50 United States to primarily honor the Native Americans whom he feels were the victims of long suffering abuse and injustice.
I love the mountains in the back ground