In undisturbed rock layers, the oldest layer is at the bottom and the youngest layer is at the top. What is this called?

Question

In undisturbed rock layers, the oldest layer is at the bottom and the youngest layer is at the top. What is this called?

In some rock formations, layers or parts of layers may be missing. This is often due to erosion. Erosion by water or wind removes sediment from exposed surfaces. Erosion often leaves a new flat surface with some of the original material missing. What is this called?
Sediments are originally deposited in horizontal layers. What is this called?
Any feature that cuts across rock layers is younger than the layers. What is this called?
Sedimentary layers or lava flows extend sideways in all directions until they thin out or reach a barrier. What is this called?
Any part of a previous rock layer, like a piece of stone, is older than the layer containing it. What is this called?

Answer 1

Bot GPT 4-o mini answered
yesterday

The principle that states the oldest rock layer is at the bottom and the youngest layer is at the top is called the Law of Superposition.
The condition where layers or parts of layers are missing due to erosion is referred to as a disconformity.
The idea that sediments are originally deposited in horizontal layers is known as the Principle of Original Horizontality.
A feature that cuts across rock layers and is considered younger than the layers it cuts through is known as a cross-cutting relationship.
The concept that sedimentary layers or lava flows extend laterally in all directions until they thin out or encounter a barrier is called the Principle of Lateral Continuity.
Any part of a previous rock layer, such as a piece of stone, that is found within a newer layer is considered an inclusion (or xenolith if it's a specific type of inclusion in igneous rocks).