This is because:
* Principle of Superposition: This fundamental principle of geology states that in undisturbed rock sequences, the oldest layers are at the bottom, and the youngest layers are at the top.
* Sedimentation Process: Sediments are deposited in layers over time, with newer sediments accumulating on top of older ones. This process, known as stratification, creates a record of geological history.
* Erosion and Uplift: While erosion can remove some layers and uplift can tilt or fold formations, the oldest layers are generally still preserved at the base, unless the entire formation has been overturned.
It's important to note that:
* Determining the exact age of sedimentary layers requires dating methods like radiometric dating.
* The location of the oldest layers can be affected by geological processes like folding, faulting, and erosion.
Let me know if you have any other questions!
