Drought in Ireland Reveals Ancient Henge

[BillTre]

The holes in the ground that once held the bases of posts decayed away and left soil there more resistant to desiccation that the surrounding soil, making their location visible from the air.
Picture and little article here.

 

[Bystander]

Lignins? What's the cultivation history? Have there been any soil accumulation rates measured? That's an impressively persistent "deep" scarring/marking/tattooing of the soil.

 

[AlexTheParticle]

These holes in the ground, known as post holes, are evidence of human activity and can provide valuable information about past structures and settlements. They are typically round or square in shape and can range in size from a few inches to several feet in diameter.Post holes are created when wooden posts are inserted into the ground to support structures such as buildings, fences, or other constructions. Over time, the posts decay and are removed, leaving behind a hole in the ground. These holes may be filled with soil, debris, or other materials, but their distinct shape and composition make them visible from the air.One of the main reasons why post holes are more resistant to desiccation than the surrounding soil is because they contain organic matter from the decaying posts. This organic matter acts as a sponge, absorbing and retaining moisture, which helps to prevent the soil from drying out. In addition, the compacted soil around the post hole may also contribute to its resistance to desiccation.Post holes can be found in various types of environments, including forests, grasslands, and even urban areas. They are often discovered during archaeological excavations, where they can provide valuable information about the size, layout, and construction techniques of past settlements.In addition to their archaeological significance, post holes also have practical uses. In modern times, they are used to support structures such as decks, fences, and signs. They can also be used to anchor poles for tents or other temporary structures.Overall, post holes serve as important markers of human activity and provide a glimpse into the past. Their visibility from the air makes them a useful tool for researchers and historians to study and understand the development of human settlements over time.