Are you overwhelmed trying to come up with geologic time scale activities for your MS-ESS1-4 lesson plans? Do you want to teach with inquiry using a phenomena-guided approach? Earth’s geologic history stretches back billions of years. Here is how I taught it in my class this year!
What vocabulary do students need for the geologic time scale?
Before diving in, students need a handful of key terms: anchor phenomena, fossils, catastrophism, uniformitarianism, relative age of rock layers, superposition, and cross-cutting. It also helps to know that Earth's history breaks into eons, then eras — Precambrian, Paleozoic, Mesozoic, and Cenozoic — divided by mass extinctions.
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Before we can delve into the world of the geologic time scale addressed in my MS-ESS1-4 lesson plans, there are several definitions we need to know.
- Anchor Phenomena: a guiding question that students will answer using information in your unit
- Fossils: the remains or shape of once-living organisms (animals, plants, and microorganisms)
- Catastrophism: a theory that states that changes to Earth’s surface (such as canyon formation, erosion, and mountain-building processes) occurred more quickly in the past than they do today
- Uniformitarianism: a theory that states that changes to Earth’s surface occurred in the past at the same rate they do today making the age of the Earth very, very old
- Relative Age of Rock Layers: how scientists determine the age of rock layers by putting them in order based on the order they occur on the Earth
- Principle of Superposition: used in dating rock layers, states that a rock layer that is underneath others must be older than those on top of it
- Principle of Cross-Cutting: used in dating rock layers, states that a rock layer that “intrudes” on other rock layers must be younger than those it “cuts” through
It is also important to know that humans break Earth’s history into eons which are then broken into eras. The four most recent eras are (from oldest to newest) Precambrian, Paleozoic, Mesozoic, and Cenozoic. These eras are divided by the types of living things that existed during those times and separated by mass extinctions.
How do you structure the unit around inquiry?
These lesson plans have students collect evidence to explain an anchor phenomenon. The teacher's job is not to give explanations right away — it's to provide activities where students discover evidence and build their own explanations. I tell students they're replicating the real scientific process.
These MS-ESS1-4 lesson plans rely on students collecting evidence to explain the anchor phenomenon in this unit. A key feature of the inquiry approach to science is that the teacher’s role is NOT to give explanations immediately. Instead, the teacher provides activities that give students the opportunity to discover evidence and develop their own explanations. I like to tell students that they are replicating the scientific process real scientists use!
What anchor phenomenon works for the geologic time scale?
I use the K-Pg boundary — the white layer found in rock across Earth. Students read that it holds high iridium levels and that dinosaur fossils only appear below it, then explain why it exists and why it matters. They'll offer many ideas, and you let them sort out which are best supported as the unit unfolds.
I chose to use the K-Pg boundary as the anchor phenomenon for this unit. I show students a picture of the white layer found in rock layers across Earth. Then, students read about what makes this layer unique: it contains higher amounts of iridium and dinosaur fossils are only found below it.
I use this as an opportunity to ask students to come up with an explanation for why this exists and why it’s important. They will come up with lots of ideas – some more accurate than others. It is important that the teacher not tell students if they are correct or incorrect. Students will determine which ideas are better supported by evidence themselves as they proceed through the unit.
How does the fossils card sort work?
Students order cards that represent rock layers using their patterns, then match them with era names. Card sorts let students collaborate, defend their reasoning, and revise ideas that don't hold up. I also point out where the K-Pg boundary sits — between the Mesozoic and Cenozoic — so students see how layers build a timescale.
Next, I give students a card sort of fossils. I love using card sorts for most of my units and include one in my MS-ESS1-4 lesson plans. It gives students a chance to collaborate, defend their reasoning, and make changes to ideas that do not make sense – basically, what scientists do in real life!
In this card sort, students use the patterns of the cards (which represent rock layers) to put them in order and match them with the names of the eras. This helps prepare students for the idea that scientists use rock layers to establish a timescale. Further, each rock layer contains fossils of organisms that appear much different than others.
I also like to show students where the K-Pg boundary layer is found – separating the Mesozoic and Cenozoic eras. Students can then begin to visualize how these rock layers are used by scientists.
How do you bring in historical context like James Hutton?
I include an article on catastrophism, uniformitarianism, and James Hutton's role. Students read how he and others proposed new ideas based on evidence they collected, which opens a discussion about how science changes over time — the same way people once believed Earth was flat or the center of the universe.
I also like to provide some historical context in my units. For my MS-ESS1-4 lesson plans, I chose to include an article about the theories of catastrophism, uniformitarianism, and the role of James Hutton. Students read about how he and other scientists proposed new ideas based on evidence they collected.
I also like to use this article as an opportunity to discuss how ideas in science change over time. They will be familiar with the idea that humans at one point believed the world was flat and that Earth was the center of the universe. As scientists collect evidence, we make new explanations and discard ideas that do not fit with the evidence.
How do you teach superposition and cross-cutting?
Solve a crime. Students examine a picture of animal footprints, car tires, and bike tires and work out the order each suspect passed through — using superposition without realizing it. Once they've explained how they knew, you give them the term. Discovering the principle themselves helps them remember and apply it.
This is one of my favorite ways to teach geologic principles – solving a crime! In this activity, students try to solve a mystery in a zoo using prints. When they look at the evidence (which is a picture showing animal footprints, car tires, and bike tires), they come up with the order in which each suspect came through the area.
I love this because they use the principle of superposition without realizing it. They explain how they knew when each suspect came through the crime scene by which prints were on top of others. As the teacher, you then tell them this is how scientists determine the age of rock layers and give them the vocabulary term of superposition. By discovering the principle themselves, they will better remember it and also be able to apply it.
What does the rock layers coring lab involve?
A hands-on lab with modeling dough layers in a plastic container. Add complexity with partial layers (erosion) or a back-filled slice (an intrusion for cross-cutting), and bury small toys as fossils. Students slice out a section, extract a core with a straw, and use the principles they discovered to place layers in relative date order.
I chose to include this lab in my MS-ESS1-4 lesson plans to provide students with a hands-on experience. All you need for this lab is modeling dough of different colors (six or so), a large plastic container, plastic plates, plastic straws, and a plastic knife. Bonus points if you have something to serve as a fossil to bury in the “rock layers”!
As you can see in the picture, simply lay down the layers in sheets. You can add some complexity by adding a half-layer (modeling part of a layer being eroded) or cutting a slice out and back-filling it with a different color (modeling an intrusion for students to use the principle of cross-cutting. Along the way, you can add in “fossils” with plastic animal toys or even sprinkles or different colors.
Students will slice a layer out of the pan and evaluate the rock layers. They will also use a straw to extract a core sample of the rock. Finally, they will use the principles they have discovered to make a relative date order of rock layers.
Even though students may have a good grasp of the concept of ordering rock layers, some practice never hurts. I like to use worksheets to practice determining the age of rock layers. But, with inquiry being the focus of this unit, students need to provide evidence to justify their order.
How does the Chicxulub crater close the anchor phenomenon?
By this point students can explain the age of the Earth and uniformitarianism. The last piece is the K-Pg layer itself. Students read a passage giving evidence for a meteor impact in Mexico around the time the dinosaurs went extinct, connecting that event to the extinction and to changes we still see today.
At this point in the unit, students understand the evidence showing how scientists explain the age of the Earth. They also can explain the idea of uniformitarianism that scientists believe today. The last piece of the anchor phenomenon is to explain how the K-Pg layer got there.
Students read a passage providing evidence for a meteor impact in Mexico around the time dinosaurs went extinct. The passage connects the events that led to the extinction of the dinosaurs and the changes to the Earth that we can see today.
Now that we have reached the end of the unit, students can summarize the evidence they have collected. They can explain how rock layers, fossils, and evidence of a meteor impact provide the basis for the explanation of the extinction of the dinosaurs. Their final challenge is to build a chain of events that links all of this evidence together.
How do you review the geologic time scale unit?
I use a no-prep digital escape room where students search a museum for password letters, plus three review games — a bingo where students find answers on pre-filled sheets, a maze they work through by answering questions, and a Google Slides game show with instant correct/incorrect feedback.
Students can always use a bit of practice. I love using digital escape rooms as a method to review important material. It makes test review much more engaging and collaborative. I made this digital escape room to do just that. They search for questions in a museum that will give them letters to a password. And best of all, it is no-prep for the teacher! Provide students with the Google Slides link, print the student response sheets, and watch them work together on this challenge!
If you would like to try this challenge with your class, click here to get it from my TeachersPayTeachers store!
For a more traditional review approach, I’ve made digital, printable, and editable versions of three different review games. If you haven’t tried using review games in your class, you are missing out!
First, I use a bingo game in which I read a clue and students find the answer on their pre-filled student sheet. Each student will have the answer on their sheet for each question to keep them engaged.
Second, I use a maze as an individual review study tool. They start at the beginning in the top-left corner and answer questions to move through the maze. If they answered all the questions correctly, they will go through each question and finish in the bottom-right corner.
Third, I have a Google Slides game show. Students click on answers to questions and move through the game. Each question tells them if they are correct or incorrect to help them study.
If you’d like to use my review games with your class, click here to check them out in my TpT store!
How do you assess the unit?
I ask students to justify which animals lived longest ago and which existed for the longest period on Earth, predict the relative ages of rocks, and provide evidence for the chain of events that led to the dinosaurs' extinction. It gauges whether they can use evidence, not just recall facts.
As much as I hate grading, I know it is important to gauge student understanding. I ask students to justify which animals lived longest ago and which lived for the longest period of time on Earth. I also ask them to predict the relative ages of rocks. Finally, I ask them to provide evidence for the events that led to the extinction of the dinosaurs.
Teaching the geologic time scale is one of the most fun units in middle school. Students typically have some background knowledge but can’t explain the evidence scientists collected to prove it. Using the inquiry approach is a great way to get students engaged and simulate how scientific discoveries really occur. At the end of the unit, they will have a much better understanding of the magnificent place we call home and all the changes that occurred before we showed up.