Geologic Time and Dating

The three eons and ten eras of the official geologic time scale.

This shows all the geologic time units of period rank.

Geologic time units from the first nine-tenths of geologic history.

Eras, periods and epochs of geologic time after the Precambrian.

Ages, epochs and periods of the Paleozoic Era, the earliest part of the Phanerozoic.

Ages, epochs and periods of the Mesozoic Era, the middle part of the Phanerozoic.

Ages, epochs and periods of the Cenozoic Era, the latest part of the Phanerozoic.

These two geologic time terms share a deep history.

The time period encompassing the most recent past was (temporarily) erased by a bureacratic bulldozer.

A brand-new name for the current time period, the Anthropocene Epoch, might get some currency.

People tell their tricks and tips for grasping millions of years.

How we learned to keep track of geologic time without using clocks or numbers.

Explaining the isotopic dating method in terms of your backyard barbecue.

Uranium-lead method is the oldest and, when done carefully, the most reliable isotopic dating method.

Potassium-argon isotopic dating is especially useful for determining the age of lavas.

Closing in on radiocarbon discrepancies through the space program pays off in knowledge about the Earth.

Who wants to be a geo-whiz? The trivia game: GEOLOGIC TIME

This online exhibit lets you zoom in and out of the billions of years of Earth history and includes some good supporting material.

A commentary by Marli Miller of the University of Oregon gives the answer to the question, and the reasons, in a lucid and commonsense way.

Click on any of the geologic ages, eras, and epochs to learn more about that part of ancient time, from the University of California Berkeley.

Geo-time mnemonics, or handy ways to keep all the geologic time units straight, from Eastern Illinois University.

This Geological Society of America time scale is still relevant for some uses; click through for the PDF.

This cooperative effort to intercalibrate and improve the world's age dating methods is the cutting edge of geochronology.

Geologist Allan Krill has been teaching his memorization technique for many years. This page shows you how to memorize all the geologic time units and their ages!

A lovely site by Leonard Miller about the oldest trees on Earth, including a section on dendrochronology.

An introduction from the Purdue Rare Isotope Measurement (PRIME) Lab.

An introductory page from the Research Laboratory for Archaeology and the History of Art, Oxford University.

The flagship journal of carbon-14 studies (and other cosmogenic isotopes) has contents, abstracts, and some sample articles online for nonsubscribers.

Roger Wiens, an Earth scientist who is a Christian, wrote this article to combat common misunderstandings among creationists about the tools of geologic dating.

Robert Ayuso of the U.S. Geological Survey describes exactly how radiometric dating studies are being used on real practical problems.

A brief version from Pamela Gore's Geology 102 course notes at Georgia Geoscience Online.

A lucid, thorough treatment of the subject from Jonathon Woolf's superb Woolf's Den that emphasizes why creationist criticisms of this technique are mistaken at best.

From the U.S. Geological Survey's pamphlet "Geologic Time" comes this basic explanation of isotope geochronology.

It's a bit sketchy, but it's the best place to learn about these hard white "corals" that I think of as the bristlecone pines of the sea.

Ellen Thomas, at Wesleyan University, posted this in-depth look at carbon isotopics and their use in studying ancient climate.

Every isotope known to science is displayed here. Click on any one for a bunch of basic physical data.

Cornell University's geology lab hosts this trip through its Thermal Ionization Mass Spectrometer. See exactly how radiometric dating is done!