2. A section cut vertically through the earth showing its different layers and allowing artefacts to be dated according to the layers in which they are found.
3. The way in which rock strata are arranged, and the chronology of their formation.
4. In geology, a branch of geology that is concerned with the systemized study, description, and classification of stratified rocks, including their origins, composition, characteristics, distribution, and correlation with one another.
Commonly these layers are levels of sedimentary rock, but stratigraphy can also include the study of non-ossified sediments; such as, those in stream beds and lake bottoms, of inclusions in volcanic ash and lava, and even the study of different layers of human occupation.
The processes of sedimentation, including the presence of certain types of fossils, provide scientists with valuable clues about the age of the earth and its history.
These principles are valuable for many different types of scientists, ranging from prospecting geologists to city planner to archaeologists and paleontologists studying human and animal history and prehistory.
2. The study of layers, or strata, in the earth.
Borrowed from geology, stratigraphy assumes that older layers are generally found on the bottom. This means that artifacts found in the upper layers of an excavation are likely to be younger than those in the lower layers.