An imprint is created when an object exerts pressure on a deformable, usually damp surface. If the surface dries out or if it is covered with sediment , for example lava , earth or dust, the shape of the contact surface of the object with the ground is retained.
Different mechanisms are conceivable:
- A stake is in the ground and is rotting; the cavity fills with other material.
- A sunken ship lying on the mud rots; new sediment layers form over it.
- A heavy basket stands on the clay ground and is being carried away; the sun dries the clay.
- A busy road is compacted by the wagon wheels. The lanes can still be made out after thousands of years.