Editing Paleontology (section)

===Geologic time===
{{main|Geologic time scale}}
[[File:Geologic time scale - spiral - ICS colours (light) - path text.svg|thumb|right|The [[geologic time scale]], proportionally represented as a [[logarithmic spiral|log-spiral]] with some major events in Earth's history. A [[megaannus]] (Ma) represents one million (106) years.]]
The earliest discussions in the field of geology centered around the possible origins of geological features and what implications these had on [[Christianity]]. The concept of a [[history of Earth]] had existed for a long time, and those who studies rocks of fossils had come to the idea of changes over time. However, in the beginning of the field of geology in the early 19th century, the most common explanation for causes of geological change were that they were the result of sedimentation during the [[Genesis flood narrative|Biblical Flood]], rather than slow processes drawn out over millions of years.<ref name="rudwick2008"/> French naturalist [[Georges Cuvier]] and his contemporaries believed that the Earth was not recently created (as in [[Young Earth Creationism]]), nor had it been around forever. They instead believed that there was a vast "prehuman" or [[antediluvian]] history. Cuvier was not the first to believe in a lengthy but finite age of the Earth, but he was the first to combine this idea with his study of fossils to suggest prehistoric events could be understood through the study of geology and the fossil record. Studies on rocks and their [[stratigraphy]] continued, including the development of [[geological map]]s highlighting the relative ages of regional [[geologic formation]]s, and it was still believed that the Biblical Flood was a primary explanation for the formation of these features.<ref name="rudwick2008-1"/> 

English geologist [[Charles Lyell]] was among the first to propose that a great flood had not occurred, and this was supported by the existence of overlapping terrestrial and marine sediment layers. He observed that the twisting, [[orogeny|uplifting]] and carving of geological features supported the idea that the [[crust (geology)|crust]] was moving continuously, and the [[sea level]] was also adjusting over time. This interpretation was not only supported by the differing levels of marine strata, but also by the shared commonality of fossils he found within them, even across large distances and at different levels above the sea. Combining these facts with his own previous work led Lyell to suggest some core principles of the history of the Earth. He suggested that here were progressive trends in the history of life, that geological history was continuously changing with periods of calm and chaos, and that the causes of these geological events were as much around in present day as in the deep past.<ref name="rudwick2008-14"/>

Following the ongoing study of geology, [[geologic formations]], and the establishment of [[geochronology]], the [[geologic time scale]] was created to separate and categorize the vast history of Earth into a scale of named geochronologic units, defined and standardized by the [[International Commission on Stratigraphy]]. The age and duration of different units has changed over time following further restudy including [[absolute dating|absolute]] and [[relative dating]] of different sediments, with the current standard recognizing four eons, ten eras, 22 periods, 37 epochs and 96 ages. Present day is recognized as the [[Meghalayan]] age, of the [[Holocene]] epoch, of the [[Quaternary]] period, of the [[Cenozoic]] era, of the [[Phanerozoic]] eon.<ref name="gradstein2012a"/> These geological time units are correlated globally through combinations of assigned times, [[index fossils]], [[paleomagnetism]], and other methods, with the correlation of taxa with time being termed [[biochronology]]. Through biochronology, paleontological events such as the evolution, extinction, or [[speciation]] of a taxon can be established at a point in time, and features such as [[mass extinction]]s can be identified.<ref name="gradstein2012b"/>