Geologic time is a fascinating topic. It is so unimaginably long it has been called “deep time”. Please learn the Geologic Time Scale as soon as possible because it is the chronological language of this course. Because you certainly don’t want to memorize all those terms, I’ve posted a pdf version of our required-time-scale. You will see that I recognize the Ediacaran before the Cambrian, and the Paleogene and Neogene instead of the old Tertiary. You need to know only the eras, periods, and Cenozoic epochs. (For the professional chart, see this beauty. You don’t need to know all these names!) William Smith was an Englishman responsible in many ways for the principles behind geologic time. James Hutton was a Scot who first effectively described and applied the concept of “uniformitarianism” in geology, which requires vast amounts of time.
Geologists distinguish between relative and absolute time, with the first being the ordering of events, and the second using measurements of time. We will most often use relative time (such as the “Cretaceous Period”) in this course, but also occasionally cite absolute time (“65 million years ago”).
The concepts of radioactive decay and its use in the dating of Earth materials take some time to master. Wikipedia has an excellent explanatory website on radiometric dating. (I’m a Wikipedia fan and editor, by the way.) A nice online radioactive decay simulation provides a visual of the process. Set the number of atoms high (I use 1600) and the time long (I use 3.0) Turn on “both” to see atoms and graph. A more detailed explanation of how half-lives are really calculated is shown here. See what I have spared you? Fortunately we have handy online calculators for radioactive decay.
As a preview of what’s coming, I give you the evolution of Homer Simpson! As another preview of coming attractions, play with this interactive globe to see what the world looked like at various times. You can even search for your hometown’s location.
You may not be surprised to learn that the scientific framework of this course is considered a lie or delusion by just over a third of Americans (which is, in fact, a new low point). “Young Earth Creationists” believe that the Earth and the Universe are a few thousand years old, and that evolution did not occur. This is radically different from the cosmological and evolutionary models supported by scientists. Creationist arguments sometimes appear scientific, but you will quickly see that they are based on misconceptions, misrepresentations, mysteries, and zealotry. For example, take a look at this page citing “evidence for a young Earth” from Answers in Genesis. These are the people who produced the multimillion-dollar Creation Museum in Kentucky (“Prepare to Believe”). Check out this visit I had with First-Year Seminar students. Don’t miss the comments by Answers in Genesis officers). These are the same people who spent millions building a full-scale version of the Ark. (Apparently visiting this Ark is a very boring experience.) We will not be covering creationist arguments directly in this course (we have real science to do), but I will always answer any questions you have. I am an evolutionary paleontologist and geologist, but please be assured that you will not be judged or graded on your personal beliefs. What you believe is always your business; what you understand about evolution and the history of life is mine.
The new Time Scavengers blog is an excellent resource for geology students, especially those interested in paleontology. University of Tennessee graduate students Jen Bauer and Adriane Lam have put together a fantastic collection of articles, teaching aids, and links just for students like you!
Finally, have a look at this website: From the Big Bang to the World Wide Web. You will have fun exploring this site. Great theme song.
Geology in the News —
On New Year’s Day, NASA’s New Horizons spacecraft flew by and photographed the most distant object observed in our Solar System: Ultima Thule. It’s a binary object looking a bit like a snowman. It is apparently reddish in true color. It will take 20 months for all the data collected to be received on Earth. Amazing.
We all know that the asteroid that slammed into the Chicxulub region 66 million years ago generated a huge tsunami that devastated southern North America. Now the global spread of this tsunami has been modeled. May we never see the likes of this in our species’ time!
The Little Ice Age ended more than a century ago, but cold seawater still lingers from that time. Cold waters that were once on the surface of the Pacific have been found very deep, and they’re still sinking. The Earth System responds to climate change on a wide range of time scales.