Visit a conventionally farmed summertime marsh today, and you will see what’s at its surface: cranberry vines (and perhaps some weeds). But if you were to dig down and pull up a plug of soil, or expose a profile, you would uncover the site’s past. Each layer of soil contributes to the health of the cranberry vine. Each layer also points to a specific event in geological or human history that in its own way helped create the right conditions for this useful fruit.
Close to the surface, you would see evidence of the recent past. You would see the current cranberry root zone (where the roots of the vine are) in the sand layers built up by farmers. (Within this layer, additional detail might evident. You might even distinguish between the layers of sand laid down during winter sanding and the organic matter that represents seasons of growth.)
Continuing your journey down through the core, beneath the sand, you would find peat, thousands of years old. Within this peat, there may even be vegetative roots, thousands of years dead, still slowly decomposing. Peat depth varies from marsh to marsh, and even from spot to spot, but can possibly be several feet deep or more.
Under the peat would be the glacial deposits: first the glacial sand particles, then a gravel layer immediately on top of the granite bedrock. This maintains a rich environment for growth.