I scarcely noticed the rock lying there, flat on its side, under a blanket of rain-soaked leaves. It was so humble, so unobtrusive, especially in a landscape of truly serious rocks, of cliffs plunging into the Potomac River and stone slabs rising like altars from the forest floor.

Yet there was something about this seemingly modest rock that brought me to a halt.

Now I could see it. An incised line ran down the rock’s left side. And that line was bisected by a second one, forming a cross. I bent over the rock and brushed away the leaves and bits of gnawed hickory nut shells. The stem of the cross ended in a diamond-shaped head, neatly chiseled. On one of the arms hung another incision, this one shaped like a carpenter’s angle.

A human story. I found this rock image last March, almost a year ago. It was a grey, chilly day, and a light rain was beginning to fall. Real adventurers shrug off such discomforts, as did I—at least for a few minutes.

What was the image’s meaning? All rocks tell stories to those who know how to read them, chronicles of mountain building, epochs of intense heat and crushing pressures, catastrophic floods, or the silent rain of skeletal fragments of tiny marine organisms into the oceanic abyss.

Some rocks go one step further and tell stories not just of the  lithosphere, but also of what Jesuit priest and geologist Pierre Teilhard de Chardin called the noosphere—the vastly more complex world of human cognition, emotions, and imagination.

Most rocks that make the leap into the noosphere speak to us in ways that we can clearly understand, such as a piece of marble carved into a Virgin Mary, or a chunk of bog iron that ends up as a pickax. But the image engraved on this rock gave no hint of its origin or its meaning. It was enigmatic, a mystery worth trying to solve.

Quick look. The rain was coming down heavier now, so I just made a quick survey. Down below, the river’s rapids and channels twisted and turned among the rocky islands. I tried to avoid looking up the hillsides on the opposite Virginia shore where a group of newly minted mansions leered at the river with their reflective windows.

Of course people have always lived along this river, first Indians, then European colonists, African slaves, and a succession of subsistence farmers and other modest folk. They lived in tiny homes, now reduced to fragments of foundations and solitary chimneys. Their owners scratched out a living from the thin soil, much like the chickens that foraged in their yards. When the government turned the land into a park in the 1970s, the people were forced to leave.

Did one of these humble people carve the image I found? Or was it someone who came along after they left? Or perhaps long before?

By now icy rivulets were trickling under my collar and my cotton hat had absorbed all the water it could. I kicked some leaves and dirt over the rock, along with a chunk of rotting limb. I would come back to search for clues over the following weeks and months and hopefully get to know a little more about the people who lived here and maybe the meaning of the rock image they created. Just maybe.