Answer:
Because of the deposits.
Explanation:
One of the reasons why rocks layers are not horizontal is because of the deposits and kinds of the walls that are next of the deposits
They are not necessarily always parallel. They have a natural inclination delimited by the walls.
This is determined by the age of the strata; the youngest deposits are taking the form of the oldest deposit.
However, part of the unique factors that determine the deposits (shape and alignment) of the layers are the organisms that lived and, therefore, could be fossilized. These factors are not repeatable since they are organisms that will not exist again.
Fossils are an essential part of the Earth's layers, as they help study the stages and shapes of the layers.
There is also another factor when magma is introduced in the form of a fault line and crystallizes in the middle of the Earth's layers. modifying the sequence of the affected rocks, becoming a young layer (not horizontal, due to its penetration into the layers of the Earth).
