It was a very cold morning and I was headed to Lamar Valley in Yellowstone National Park. The scenic view at Alum Creek was a beautiful purple, shining in the mist. I stopped to capture it, at the risk of missing the wolves in Lamar. I heard a thunderous sound over my left should while facing to the right and shooting the beauty of the morning. This bison herd thundered down the hill right next to me and one by one, entered the frigid water. I'll never forget the sound or the feeling I had. I was very fortunate to have the presence of mind to turn my camera toward them and capture a few shots.