Underfoot: Life on a Rock

By: Susan Sprout

 A huge bolder standing in a rather flat area of woods caught my eye on our Earth Day rambles. I knew it was a glacial erratic because there were no other big rocks nearby. Ripped out of its bed and plucked up by a moving ice sheet, it was unceremoniously dumped there as the glacier melted.

Glacial Erratic

Thousands of years later, it has become a microcosm of lichens, mosses, grasses and trees. The non-living environment of the rock was a stable platform or substrate for lichens, typically the first organisms to colonize bare rock. Their physical and chemical processes dissolved minerals and built up soil as they lived and died. Mosses began living on the rock next when sufficient soil was available. Then came grasses and shrubs. Living and dying there, they provided more humus and soil to the rocky top.

Moss and lichen thrive on the rock’s surface.

OK, confession time…what really caught my attention as I passed by the rock… were the American Beech trees growing on top of it, like candles on a cake! Happy B-Earth Day! May all of the ecosystems on earth keep working for all of the organisms that share the planet and make it livable for each other! Humans, take note.

Catch up on past issues of Underfoot!