Relative dating
Relative dating
Relative dating is the science determining the relative order of past events, without necessarily determining their
absolute age.
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 which provided a means
of absolute dating in the early 20th century,
archaeologists and geologists were largely
limited to the use of relative dating
techniques to determine the geological
events.
Though relative dating can only determine
The Permian through Jurassic stratigraphy of the Colorado Plateau area of
the sequential order in which a series of
southeastern Utah is a great example of Original Horizontality and the Law of
Superposition, two important ideas used in relative dating. These strata make up
events occurred, not when they occur, it
much of the famous prominent rock formations in widely spaced protected areas
remains a useful technique especially in
such as Capitol Reef National Park and Canyonlands National Park. From top to
materials lacking radioactive isotopes.
bottom: Rounded tan domes of the Navajo Sandstone, layered red Kayenta
Relative dating by biostratigraphy is the
Formation, cliff-forming, vertically jointed, red Wingate Sandstone, slope-forming,
purplish Chinle Formation, layered, lighter-red Moenkopi Formation, and white,
preferred method in paleontology, and is in
layered Cutler Formation sandstone. Picture from Glen Canyon National
some respects more accurate (Stanley,
Recreation Area, Utah.
167–69). The Law of Superposition was the
summary outcome of 'relative dating' as
observed in geology from the 17th century to the early 20th century.
The regular order of 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. As he continued his job as a surveyor, he found the same patterns across England. He also found that
certain animals were in only certain layers and that they were in the same layers all across England. Due to that
discovery, Smith was able to recognize the order that the rocks were formed. Sixteen years after his discovery, he
published a geological map of England showing the rocks of different geologic time eras.
Principles of relative chronology
• Uniformitarianism (Hutton) Popularized by Charles Lyell
• Law of superposition (Steno)
• Original Horizontality (Steno)
• Lateral continuity (Steno)
• Cross cutting relationships (Hutton)
• Inclusions of Igneous rocks (Hutton)
• Principle of faunal succession (Smith)
• Law of included fragments
1
Relative dating
Archaeology
Relative dating methods in archaeology are similar to some of those applied in geology. The principles of typology
can be compared to the biostratigraphic approach described above.
Planetology
Relative dating is used to determine the order of events on objects other than Earth; for decades, planetary scientists
have used it to decipher the evolution of bodies in the Solar System, particularly in the vast majority of cases in
which we have no surface samples. Many of the same principles are applied. For example, if a valley is formed
inside an impact crater, the valley must be younger than the crater.
Craters themselves are highly useful in relative dating; as a general rule, the younger a planetary surface is, the fewer
craters it has. If long-term cratering rates are known to enough precision, crude absolute dates can be applied based
on craters alone; however, cratering rates outside the Earth-Moon system are poorly known.(Hartmann, 258)
References
• "Biostratigraphy: William Smith". Understanding Evolution. 2009. University of California Museum of
Paleontology. 23 January 2009 <http://evolution.berkely.edu/evolibrary/article/0_0_0/history_11>
• Hartmann, William K. Moons & Planets, 4th ed. Belmont: Wadsworth Publishing Company, 1999. ISBN
0-534-54630-7
• Monroe, James S., and Reed Wicander. The Changing Earth: Exploring Geology and Evolution, 2nd ed. Belmont:
West Publishing Company, 1997. ISBN 0-314-09577-2
• Stanley, Steven M. Earth System History. New York: W.H. Freeman and Company, 1999. ISBN 0-7167-2882-6
2
Article Sources and Contributors
Article Sources and Contributors
Relative dating Source: http://en.wikipedia.org/w/index.php?oldid=457198710 Contributors: Aff123a, Andycjp, Archy33, Arjun01, Arthena, Awickert, Ayudante, Ben Ben, ChrisCork,
Condem, Courcelles, Cpl Syx, DVdm, Dandv, DarkElf109, Darklilac, Delirium, Diego Grez, Discospinster, EoGuy, Erimus, Ernest3.141, FeralFace2, Flopdonk, Frebel93, Gaius Cornelius,
Goodmanjm, Grsz11, Grumpy444grumpy, Hanacy, HappyInGeneral, Hi878, Hirudo, Hmains, Hotcrocodile, Inq314, JV Smithy, Jacob Haller, JeremyA, Jnothman, John254, JonMcLoone, Julius
Sahara, KGasso, Kjkolb, Kukini, Lightdarkness, LilHelpa, Macrakis, Magioladitis, McSly, Meanos, Michael.passman, Mididoctors, Mmcannis, Mwtoews, N5iln, NawlinWiki, [email protected],
Pearle, Phi*n!x, Philip Trueman, Qfl247, Quentonamos, RaseaC, Rdmbox, Redsen5, RevRagnarok, RossPatterson, RoyBoy, Salomike, Sceptre, Shadowjams, ShadowoftheL1ght, Shawnhath,
SparkyG66, Sscgirl, TNTfan101, Tbhotch, The Captain Returns, The Talking Toaster, The wub, Tide rolls, Tom5895, Uncle Dick, Viv Hamilton, Vsmith, Welsh, Wikipelli, William Avery,
Woohookitty, Xnuala, Yamamoto Ichiro, Yamara, ZOMG.co, 177 anonymous edits
Image Sources, Licenses and Contributors
Image:SEUtahStrat.JPG Source: http://en.wikipedia.org/w/index.php?title=File:SEUtahStrat.JPG License: Creative Commons Attribution-Sharealike 3.0 Contributors: Qfl247 (talk)
(Transferred by Citypeek/Original uploaded by Qfl247)
License
Creative Commons Attribution-Share Alike 3.0 Unported
//creativecommons.org/licenses/by-sa/3.0/
3