What is the geologic time scale? If you are teaching Earth history, you need to help your students answer this question before they can jump in and learn about it. Earth’s 4.6 billion-year history is too big to think about all at once, so scientists divide it into eons, eras, periods, and epochs. Each time period begins and ends with a major change to Earth’s environment.
A Definition of the Geologic Time Scale
A working definition is helpful for explaining the geologic time scale to students. The geologic time scale is a system for organizing the time in Earth’s history. It is like a calendar. The largest divisions, eons are like months, the eras are like weeks, the periods are like days, and epochs are like hours.
You can teach your students many mnemonic devices to help them remember the order of the eons, eras, periods, and epochs, but I suggest having students make their own. This fun activity will encourage collaboration within groups, and students are more likely to remember their own mnemonic devices. You will have to decide how much and what parts of the geologic time scale students need to memorize. For example, you probably want students to know all of the eons in order, but they might not need to know the Jurassic period’s epochs.
Understanding the Geologic Time Scale
If you have been researching online, you will see that the geologic time scale dates are not always exactly the same. This system was only invented in the 1900s. As scientists learn more about the Earth’s history from new findings and advancements in technology, they update the timescale. Of course, there are many heated debates before any changes are widely accepted. As a result, you and your students may find different dates in different places.
I like to remind students that the geologic time scale encompasses nearly five billion years. It is going to be hard to pinpoint anything over that vast stretch of time. Also, major events didn’t happen overnight on Earth. An event that seems sudden, like the Cambrian Explosion, actually happened over millions of years.
Also, many resources, especially those for middle school students, start the geologic time scale at the Paleozoic Eon. They call everything before it Precambrian Time or the Precambrian Eon. I like to teach students about the Hadean and Archaean Eons because this is a fascinating part of Earth history.
How to Teach It
If you are teaching your middle school science students about earth history, you want to make sure you have the information they need and an activity to keep them engaged in the topic. My geologic time scale workshop activity has everything you need to introduce this important topic to your students.
The activity includes a reading passage and comprehension questions. It gives students the necessary background information on the geologic time scale. During the workshop, students work together to create their own model using butcher paper. After the workshop, you can assess what your students learned with a quiz.
Exploring Earth History
Once your students have been introduced to the geologic time scale, they will be ready to confidently explore the rest of Earth’s history. They will see how Earth’s landscape and life have changed over the last 4.6 billion years.
Hadean Eon
Archean Eon
Are You Teaching Another Science Topic?
I am working on creating more science units so that every science teacher can get exactly what he or she needs for her students. You can also read about how I use brain science to teach other science topics on my blog. Click the pictures below to learn more.
Coming Soon!
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