The type of unconformity where an erosional surface exists between several horizontal layers is called a disconformity.

Here's a breakdown:

* Unconformity: A boundary between two rock sequences that represents a period of erosion or non-deposition.

* Disconformity: A type of unconformity where the layers above and below the erosional surface are parallel. This indicates a period of erosion or non-deposition occurred within a single, generally horizontal sequence of sedimentary rocks.

Let me know if you'd like to explore other types of unconformities!