I have heard of this special park and I did not realize that it was right on my route. A pleasant surprise. https://www.nps.gov/pefo/index.htm This will give you some official info and more photos.
Volcanoes nearby erupted and covered the forest with ash. This covering kept the air and organisms from eating the trees and the mineral rich water helped the hardening process.
I love my riding days and look to find interesting and informative items to share.