Wet leaves are easier to see, of course. The resemblance to black ice is in the slickness and the difficulty of assessment. How wet are they? How rotten, and how deep? The more fortunate connection is that black ice and wet leaves both fade in the warmth of the day.
Just as Yury suggested, the shallow excavations later topped with concrete are the foundations of new benches. The one below is on the outbound side of the trail west of Wiggins Avenue in Bedford.
It's hard to keep track, but I don't think this tree leaning out from the tree line used to be so prominent. My guess is that its great height and the rain-softened ground are slowly tilting it over the trail just outbound from Fletcher Avenue in Lexington. There are high wind warnings tomorrow afternoon into Wednesday morning. Don't stand right there.
Today: 13 miles. This year: 1493.7 miles.