SPS: East Donegal Riverfront Park

Last Saturday, we went for the first time to the Township park three or four miles down the road from us. In the summer, the Susquehanna river runs wide and very low through this area, exposing a lot of rock that is usually under water at other times of the year.

Here's a general view. I am sure that the rocks I am standing on are underwater, or near to it, when the river is high, but now they are far above the water level.

In a cleft in the rocks, a stranded puddle bubbled with bright green algae. It looks like something from another planet.

I think I remember learning, in school, that holes like these form in river bottoms when smaller, rounded rocks become stuck in a depression. The current then agitates the rock, turning it around and around, and slowly a hole is drilled. Some of these are over a foot deep, it must've taken generations to form them!

Lastly, I found a butterfly checking out the clover in the park's picnic area. Anyone know what kind it is? This one's unfamiliar to me.