Stratigraphy is a term used by archaeologists and geoarchaeologists to refer to the natural and cultural soil layers that make up an archaeological deposit. Geologists and archaeologists alike have noted that the earth is made up of layers of rock and soil that were created by natural occurrences—the deaths of animals and climatic events such as floods, glaciers , and volcanic eruptions—and by cultural ones such as midden trash deposits and building events. Archaeologists map the cultural and natural layers that they see in a site to better understand the processes that created the site and the changes that occurred over time. Modern principles of stratigraphic analysis were worked out by several geologists including Georges Cuvier and Lyell in the 18th and 19th centuries.
Stratigraphy (archaeology) - Wikipedia
Relative dating is the science of determining the relative order of past events i. In geology, rock or superficial deposits , fossils and lithologies can be used to correlate one stratigraphic column with another. Prior to the discovery of radiometric dating in the early 20th century, which provided a means of absolute dating , archaeologists and geologists used relative dating to determine ages of materials. Though relative dating can only determine the sequential order in which a series of events occurred, not when they occurred, it remains a useful technique. Relative dating by biostratigraphy is the preferred method in paleontology and is, in some respects, more accurate.
Relative dating is used to arrange geological events, and the rocks they leave behind, in a sequence. The method of reading the order is called stratigraphy layers of rock are called strata. Relative dating does not provide actual numerical dates for the rocks. Next time you find a cliff or road cutting with lots of rock strata, try working out the age order using some simple principles:. Fossils are important for working out the relative ages of sedimentary rocks.
Melissa graduated from NC State University with a Bachelor's Degree in geology in and currently works as a lab technician. Figuring out the geologic history of an area seems like a daunting task, but there are several strategies that geologists use to figure out which rocks are older than other rocks, and what geologic processes occurred in a particular order. Geologists can numerically date certain rocks by using the radioactive decay of elements trapped in rocks or minerals to figure out their exact age.