New Haven Independent

Twenty people met on the East Rock Road Bridge over the Mill River for the first phase of the walk. Copeland MacClintock, or “Cope” as he is referred to, began by handing out sample pieces of rock, getting us to observe them and then giving us detailed information about what we were seeing, where it came from, and how it was formed. And this is how our walk progressed.

We looked at small hand-held samples of rock or we looked at ledges high on East Rock. It all was part of a much bigger picture that played into the formation of not just East Rock but of the entire Connecticut-Long Island area.

The course of the walk headed north to Whitney Circle above the dam, on to Whitney Peak, then South to the area around the head of the switchback trail, and then back down the trail returning to the Mill River bridge.

We learned that the hills of the Central CT lowlands are all made of basalt. Our area is very rich in iron and during the Revolutionary War period was one of our country’s primary sources of iron. From rock samples we learned that the orange to brown coloring we see is caused by the presence of this iron. We learned where there are outcroppings of sedimentary rock, saw faceted pebbles of quartz that were plained by the glaciers, and learned other features of rock that were created by the glaciers. We learned the difference between the various sedimentary particles including clay, silt, sand, pebbles, cobble, and boulders. We saw glacial erratics and markings on boulders from stones that were dragged by a glacier.

On the backside of the head of the switchback trail of East Rock, Cope had us look at a quartz crystal about the size of a 50 cent piece on the huge basalt wall. This small crystal was evidence of the glacial process that occurred here millions of years ago. But nearly as amazing as all of that was to me was the realization that Cope had found this tiny quartz specimen on this mighty, towering basalt wall.

From small, simple, hand-made diagrams we learned how the formation of the East and West Rock area is related to the formation of the Palisades on the Hudson River in New Jersey.

In general the walk and what Cope had to offer was a huge outpouring of information. I left the walk with my head spinning, feeling like I had just had a whole geology course in 3 hours, and thinking that I had better do this one again because I had so many questions to ask and information I wanted further clarified. But we were given a good resource in planning for the walk which is available online for further study: The Face of Connecticut-People, Geology, and the Land by Michael Bell, State Geological and Natural History Survey of CT, Bulletin 110, 1985 I think I will also consult with that to learn more.