Principle of original horizontality: This principle simply states that deposition of rocks occurs horizontally or nearly horizontally. Most deposition occurs as the ocean deposits sediment flat and horizontally on existing rock, either on the ocean floor or on the continent.Sediments can be deposited on an incline, but this doesn't happen very often.For example, a fossil bone found in limestone is necessarily older than the limestone surrounding it.Stratigraphy is a branch of geology that studies rock strata with an emphasis on distribution, deposition, age and evidence of past life.Conversely, the igneous rocks are younger than the sedimentary rocks.Other examples of cross crutting relationships can be related to faults (fault has to be younger than the rock it is found in) and unconformities (see below).As sediment weathers and erodes from its source, and as long as it is does not encounter any physical barriers to its movement, the sediment will be deposited in all directions until it thins or fades into a different sediment type.
The rock containing the inclusion formed around the already existing rock, thus preserving it inside.The first is called absolute dating, where geologists use radioactive decay to determine the actual age of a rock. Let's say you are a geologist who is tasked with dating the rocks found in the Grand Canyon, and you must do so in the canyon without the aid of any laboratory equipment. Relative dating doesn't really give us an actual 'age,' but it does put things in sequential order.This allows geologists to determine the age of a rock or strata relative to another rock or strata.For purposes of relative dating this principle is used to identify faults and erosional features within the rock record.Then, by applying the Principle of Cross-Cutting we are able to relatively date those processes.