Plowed fields generate surface rocks each spring while forests do not
Evidence
Sites without perennial roots allow rocks to surface each spring. As the ground freezes and expands in the winter, rocks are ferried upward, leaving a hollow below them. Contrary to popular opinion, at the end of the winter the ground begins to thaw from the bottom up, not the top down. Below the frost zone the earth has a consistent temperature around 50–55 degrees F. As the winter abates, the thaw creeps upward, collapsing the hollow beneath each rock. When the rock is released by thaw, it can’t drop back down to its original position. In this way, over the course of years rocks are slowly carried to the surface, where they have to be removed since they get in the way of working the soil. Rocks don’t surface in forests or hay fields since the perennial roots of trees, shrubs, and grasses lock each rock into place so that the ground freezes and thaws as a unit. Only cultivated sites generate small rocks each year. — Tom Wessels, Forest Forensics, 80
Categorization
- XREF: Frost-heaving of rocks is a classic soil/geomorphology process; grounds the ‘rock line as field-history marker’ technique. — connects to: Enigmatic stone cairns sometimes defy utilitarian agricultural explanation — Tom Wessels, Forest Forensics: A Field Guide to…, 22; Tilled agricultural soil lacks the self-organized web of forest soil — Robin Wall Kimmerer, Braiding Sweetgrass: Indigenous Wisdom,…, 844