Happy New Year Kossacks!
You can see the first diary here Christmas Weekend Hiking (A Photo Diary)
Rock Dam is an area here in Dickinson County that is just being developed for hiking. It is a rough & rugged area. We have hiked there before but decided that it was worth revisiting on our Christmas weekend hikes. At Rock Dam, the rocks are the real star of the show.
The surface rocks at Rock Dam are a very pure form of Quartzite known as Sturgeon River Quartzite. Often snow white with some pink and red, it is semi-translucent & would be lapidary grade as it takes a brilliant polish. Massive blocks with sheer sides are covered with a fascinating array of lichens, mosses & fungus. The vertical sides are usually adorned with hanging gardens of the same as well as ferns. Tiny red pines somehow survive in narrow cracks.
Perhaps of more interest are the rocks that lie just beneath the Sturgeon! These rocks are the famed Carney Lake Gneiss. This Gneiss is thought to be roughly 2,700 million years old, thus are some of the oldest rocks ever found. They are an ancient crustal formation that was nearly consumed by an approaching ocean basalt plate from the south. The crustal plate was subducted by the basalt plate roughly at the Wisconsin-Michigan line at what is known as the Niagara Suture Zone. For those geologically inclined, a good reference source would be INSTITUTE ON LAKE SUPERIOR GEOLOGY 49th Annual Meeting which contains a good explanation of this area as well as many others in this fascinating area.