I had another free day this weekend and decided to head out to a forest reserve I had never visited before. The reserve has mixed stands of pine and hardwood that ring along the slopes and valleys that border the reserve's central lake. The undulating slopes of these hills bare the scars of ancient glaciation, as evidenced in part by the many large, glacially weathered, granite boulders that dot the landscape.
It is estimated that around 20,000 years ago, during the last glacial maximum (LGM), the ice-cover in this region of North America was up to 1 mile thick. Slowing scouring the landscape beneath its tremendous weight over thousands of years, the glaciers would only spare the largest and sturdiest igneous and metamorphic rocks, while softer sedimentary rocks would be ground into the fine, silica-rich sands that the North American Great Lakes are famous for.
(Image Source: https://www.semanticscholar.org/paper/Glacial-landsystems-and-dynamics-of-the-Saginaw-of-Kehew-Esch/f047b807478e3e85c10f08aed5497d98413439ff)
Rocks that are carried over great distances by glacial flows and deposited in new locations are known as "glacial erratics" when found terrestrially and "glacial dropstones" when found embedded within marine sediments. Additional evidence for glaciation on the erratics themselves can be seen in the form of "glacial striations" as well as "chatter-marks," both geologic indicators of prior glacial activity. When found in bedrock, such markings can be used as directional indicators of previous glacial flow since glacial striations run parallel to the former flow direction and chatter marks are oriented such that their crescent shape is perpendicular to the direction of flow. Both marking types are imaged below.
Erratics:
Large crystal size (can be seen with naked eye) shows that the minerals cooled and crystallized slowly to form a rigid structure --> Igneous intrusion
Demonstration of how differing hardness of rock layers influences weathering rate (harder rock has not erroded as much over time --> protrudes from surrounding softer rock layer)
Glacial Striations:
Chatter Marks:
Apart from the stones, I was able to find plenty of fresh fungal fruitings as well as the foundation to an old home that used to sit at the edge of the lake. The most abundant type of fungi I found was artist's bracket (Ganoderma applanatum), though I did find several other species as well. I have attached images along with what I assume are the correct species IDs. Please correct me if you beleive I am wrong!
Artist's bracket (Ganoderma applanatum):
Northern cinnabar polypore (Pycnoporus cinnabarinus):
Oak Maze Gill(Daedalea quercina):
Witch's butter (Tremella mesenterica)
Turkey tail fungus (Trametes versicolor)
Lumpy bracket (Trametes gibbosa):
Old home by the lake:
Must have been quite the view.
I hope you enjoyed walking with me.
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