A standard definition of geology is the history of the earth and its life, especially as it's recorded in rocks. (Merriam-Webster)
I introduce students to the definition of geology and then ask them, “What can rocks tell us about the past?” I record their responses on a chart paper or project them on lined paper using a document camera. The typical response is usually related to fossils. I record their answers on a chart and then probe further. “If rocks do not contain fossils, what else can we still learn from them?” This is where the conversation usually wanders into confusion. Students may comment about volcanoes, or possibly about sediments. I record these responses as well. Then I explain to the students, "Rocks can teach us about past environments even if they don’t have fossils. Sedimentary rocks might tell us about ancient rivers, lakes, oceans, or sand dunes. Volcanic rocks can tell us what type of volcanic activity went on in an area, nearby, or deep under the ground. Metamorphic rocks are trickier, but they too can tell us about which types of volcanic or sedimentary rocks were crushed, heated, and changed (metamorphosed), and possibly when or why."
Here are examples of how I would use geology maps from New Hampshire, Texas and Tucson (AZ).
We aren’t going to worry about any of these specifics. What I want you to look for today are patterns and other interesting details. I am going to show you one way in which scientists can break the code to the past. The second thing I want you to focus on is saying/writing (depending on the time of year and the level of the students) your observations in complete sentences. Be careful not to state an opinion as a fact, and to only record that which you can definitely observe.
I lead students through the Geology Map Activity Alaska, leaving plenty of time for questions, observations, and discussion. I use chart paper to continue to record their questions and evolving thoughts about what rocks can teach us.
Here is an example of what one student wrote for her geology observation notes. Here is an example of above level geology observations. As I introduce a new idea, I still differentiate for struggling students, English language learners, and advanced students. I also stay vigilant for misconceptions and remind myself that the basic ideas I want them to leave this lesson with are:
1. Rocks tell stories that scientists can interpret using many tools.
2. A simple tool used by scientists is a geologic map.
3. Rocks provide us with records of many different past events.
4. We can come up with basic statements a out the geology of a state by using a geologic map.