The idea of the Earth developing in a series of layers, also known as the layer cake model, is a widely accepted theory in geology known as the Principle of Superposition. This principle suggests that in undisturbed sedimentary rock sequences, the oldest rocks are found at the bottom, and progressively younger rocks are deposited on top. Several lines of evidence support this concept:

1. Stratigraphy: The study of rock layers, or strata, has revealed that most sedimentary rocks are deposited in horizontal layers. These layers are formed as sediments, such as sand, mud, and gravel, are transported and deposited by various geological processes like water, wind, and gravity. Over time, the weight of the overlying sediments compresses and solidifies the lower layers, creating distinct rock strata.

2. Relative Dating: Relative dating techniques enable geologists to determine the sequence of events and the relative ages of rocks based on their positions within a stratigraphic sequence. By observing the sequence of rock layers and identifying specific geological markers or index fossils, scientists can deduce which layers were formed earlier and which were deposited later.

3. Uniformitarianism: The principle of uniformitarianism states that the geological processes and laws that operate today are the same as those that have occurred throughout Earth's history. By studying modern sedimentary environments and processes, geologists can infer how ancient sedimentary rocks were formed and deposited, providing insights into the Earth's past layering.

4. Paleontology: The study of fossils found within sedimentary rocks helps date different rock layers. Index fossils, which are species with short geologic ranges and broad geographic distribution, serve as time markers. By identifying the index fossils in different layers, geologists can determine the relative ages of the strata and correlate rock formations across vast distances.

5. Radiometric Dating: While relative dating determines the sequence of events, absolute dating methods like radiometric dating provide numerical estimates of the age of rocks and minerals. By analyzing the decay rates of radioactive isotopes found in certain minerals, scientists can calculate the age of rock formations and corroborate the relative ages determined through stratigraphy and paleontology.

These lines of evidence collectively support the concept that the Earth developed in a series of layers, with older layers at the bottom and younger layers on top in undisturbed sedimentary sequences. This layering is the result of continuous geological processes that have occurred throughout Earth's history, including sedimentation, compaction, and the preservation of geological records in rock formations.