Methods for relative dating were developed when geology first emerged as a natural science in the 18th century.
The regular order of the occurrence of fossils in rock layers was discovered around 1800 by William Smith.
While digging the Somerset Coal Canal in southwest England, he found that fossils were always in the same order in the rock layers.
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.
These strata make up much of the famous prominent rock formations in widely spaced protected areas such as Capitol Reef National Park and Canyonlands National Park.
From top to bottom: Rounded tan domes of the Navajo Sandstone, layered red Kayenta Formation, cliff-forming, vertically jointed, red Wingate Sandstone, slope-forming, purplish Chinle Formation, layered, lighter-red Moenkopi Formation, and white, layered Cutler Formation sandstone.
Finding the key bed in these situations may help determine whether the fault is a normal fault or a thrust fault.
The principle of inclusions and components explains that, with sedimentary rocks, if inclusions (or clasts) are found in a formation, then the inclusions must be older than the formation that contains them.
Our scientists develop new methods and tools to supply timely, relevant, and useful information about the Earth and its processes.
The Permian through Jurassic stratigraphy of the Colorado Plateau area of southeastern Utah is a great example of Original Horizontality and the Law of Superposition, two important ideas used in relative dating.
Photo from Glen Canyon National Recreation Area, Utah.