A Rock's History
To gather some appreciation of our world, especially our rock world, we are going to gather an assortment of rocks from our campus. You will use a rock key to classify some of the samples we collect.
- The class will go outside to collect an assortment of rocks. You will need to collect at least one sample to use for the remaining procedures. Please stay with the class and observe boundary restrictions on our hunt.
- From the rock assortment, choose one sample. Draw a picture of the details in your sample. Remember to use color to enhance your observations. List the physical characteristics.
- Follow the instructions to determine if your sample is metamorphic, sedimentary or igneous rock.
- Are your crystals large enough to see using the magnifying glass? Or with a microscope?
- What do you see using the magnifying glass or microscope?
- Can you see different types of materials within the same rock (fossils, layers of different material, color contrast)?
- Would you classify rocks as a mixture? Why?
- What step on the rock key helped you to identify your rock?
When writing a conclusion on a lab, please summarize the lab procedures you found helpful in solving the problem presented. Summarize the findings of your experiment (classifying your rock sample). What did you like most about this lab?
Ninety minutes to two hours.
Instructional Support Downloads
Task Write Up
Materials for this task include magnifier, safety goggles, hammer, nails, microscope, bucket, newspapers for tables, HCl (optional), resource books and rock identification charts, notebooks, 3x5 index cards and pencils for taking field notes.
Common white vinegar, a less caustic acid than HCl, can also be used to detect the presence of limestone or dolostone (rich in calcium and magnesium carbonates). Pouring a small amount of vinegar onto the rock sample will produce “fizzing” as the acid reacts with the base elements in the rock. (Note: Limestone will bubble much more than dolostone. Placing acid on powdered dolostone, scratched out by a knife or nail, will create more of a fizz.)
This is the final activity for my students’ rock and mineral unit. The students have covered mineral composition, crystal patterns, characteristics of rocks and basic identification strategies. We have identified 30 common minerals. The students have studied the rock cycle, erosion and weathering, and rock classifications. Students should have a working knowledge of rock identification tests to apply to samples they have collected on our school campus.
This activity gives students the opportunity to apply the observation, data gathering and analysis skills they have learned to their immediate environment. It allows the teacher an opportunity to assess a student’s application of various investigation skills practiced in a laboratory setting. It also encourages students to become actual geologists as they study, theorize about and identify geological processes occurring around their school. This inquiry activity is broken down into a two-day lesson.
The inquiry actually begins on the first day of the rock and mineral unit. I introduce our final activity as a challenge to the students. They will be able to identify rocks by their classifications: sedimentary, igneous or metamorphic. I always have someone who says, “We don’t have any rocks around our school.” (Oh, the challenges!) On day one of the inquiry activity, students are instructed on the task, collecting rocks. Each student is expected to collect at least one sample and bring it back to the classroom. I carry a geologist's hammer or a claw hammer, my goggles and a magnifier. I also ask someone to carry a large bucket for all the extra rocks we may want to collect. We stay within a defined space. I like to give directions, such as, “We will start at the football field and work our way south, down the slope onto the lower soccer field; we will then cut back to the parking area, and then back to the lower sidewalk, and return to the classroom.” This gives students a general sense of direction when working outdoors. Students might also carry a 3x5 index card with them to jot down notes about where they found the rock sample, if there were many rocks of this type in the same area, etc.
Day two begins with each student selecting one rock to study further. I provide rock identification keys, magnifiers, colored pencils, nails for the hardness test, hammers to break rocks (to expose clean faces), soap, water, and HCl for the acid test (this last test I will do for the students upon request). Students should be instructed to make an accurate drawing of their rock (they could also include a scale for size) and then begin the process of identifying their samples by conducting various tests. It is important to remind students to look for small fossils as they work. We study fossils later in the year, and this activity lays the foundation for those studies.
Students will be introduced to the topic of fossils later in the year; this task can be extended to include an investigation of fossils and fossil evidence. Outside explorations also allow the teacher to point out signs of (physical and chemical) weathering, erosion, deposition and soil composition. Students could also create their own rock and soil identification keys and geologic maps of the school grounds, using county soil maps as a resource.
Ask students if they can find any evidence that the geologic history of an area has affected the development of the area's economy (e.g., tourism), its use of natural resources (e.g., mining, agriculture), its legal practices, etc.
Many myths and tall tales (e.g., Paul Bunyon stories) are connected to the geological history of a region. Students could research and write both factual and fictional versions of famous rock formations, fossil evidence and geological events. Using their selected rock samples, students could create a “family album” describing its formation and geologic history.
Understandings About the Nature of Science (see appendix)
I recruit a fellow teacher to help with class management while outdoors. Students will tend to lag behind, or move ahead, and it is helpful to have someone with each group. You should scout areas ahead of time find some potential rock sources and varieties. Good locations are on slopes, at the end of drainpipes, around eroded ditches and in tilled topsoil. It would be helpful to know the geologic processes that occurred in your area, but it is not a requirement. (Local museums and county agencies might be helpful here.) Your students will begin to develop some theories by the end of this investigation.
Cover your tables with old newspapers. Break rocks inside a rolled newspaper to prevent fragments from flying and possibly striking students. Safety goggles are recommended when breaking rocks.
Some questions to guide the inquiry might include:
- Do you see any fossils in the rocks you are examining? (only sedimentary rocks hold fossils)
- What is it about the rock that caught your eye? color? size? luster? shape? hardness? cleavage? fluorescence? location?
- Does it remind you of any rocks we’ve already studied?
- Did you note the location of your rock? Were there many rocks of the same type in that area? Was it on a slope? At the end of a drainage area?
- How do you think the rock got to the place where you found it? What is the soil like in that area?
- What characteristics of the rock will help you to identify it later in the lab?
(Unifying concepts/big ideas and science concepts to be assessed using the Science Exemplars Rubric under the criterion: Science Concepts and Related Content)
Earth Science – Earth System; Earth's History: Students identify the characteristics of rocks that reveal information about their composition (minerals and plant and animal remains) and formation (erosion, transport, deposit, pressure, temperature, etc.).
Physical Science – Properties of Matter: Students observe, identify and classify rocks and minerals according to their properties.
Mathematics: Students use diagrams and precise measurements. Students collect, organize and analyze data appropriately.
Specific solutions will vary depending upon the samples collected. Solutions should include data related to characteristics observed in the lab and/or outside. Assessment should be based on the student's ability to apply prior knowledge and appropriate tests (e.g., hardness) and use identification keys and scientific tools (e.g., magnifiers) appropriately.
The student’s drawing of the rock sample shows some detail but lacks labels describing the rock’s physical characteristics. No specific color indicators are noted in the drawing. The student shows evidence of using tools (magnifier and microscope) but identifies crystals only through their use, when other items could also be seen (sand particles, different layers, colors, etc.). The student classifies rocks as a mixture but provides no viable explanation – indicating a lack of understanding of the scientific term or its meaning. No conclusions are given. No procedures are summarized, indicating a lack of a strategy for investigation.
The student’s drawing of the rock sample shows some detail but lacks labels describing the rock’s physical characteristics. No specific color indicators are noted in the drawing. The student identifies the rock as metamorphic but later describes characteristics of sedimentary rocks, indicating some understanding of observable characteristics but a lack of understanding in how to use the identification key. The student shows evidence of attempting to use tools (magnifier and microscope) appropriately and identifies no crystals, some sand particles, fossils, and “hairy, pokey things like a porcupine.” The student classifies rocks as a mixture and provides an explanation with examples (sand and shells) – indicating some understanding of the scientific term. Limited conclusions are given, using only the identification key, indicating a partial strategy for investigation.
The student’s drawing of the rock sample shows some details and lists three of the rock's physical characteristics (rough, foliated, muddy). Dark and light colors are indicated in the drawing. The student identifies the rock as sedimentary and later describes several appropriate characteristics, indicating an understanding of observable characteristics but a lack of understanding that “foliated” applies only to layering in metamorphic rock. The student shows evidence of attempting to use tools (magnifier and microscope) appropriately and identifies no crystals; tan, brown, white and gray colors; dirt and rock fragments; and a fossil. The student classifies rocks as a mixture and provides an explanation with examples (soil, rock particles, crystals) – indicating some understanding of the scientific term. Conclusions are based on appropriate procedures, including use of the rock identification key and other tools and on an analysis of observed properties, indicating a successful strategy for investigation.
The student’s drawing of the rock sample shows details and lists numerous physical characteristics (rough, size of palm, ridges, colors, etc.). The student identifies the rock as sedimentary and later describes appropriate characteristics, indicating an understanding of observable characteristics of sedimentary rock. The student shows evidence of attempting to use tools (magnifier and microscope) appropriately and identifies surface features, colors, sand, little rocks and a fossil. The student classifies rocks as a mixture and provides an explanation with examples (sand and gravel) – indicating some understanding of the scientific term. Conclusions include a more full explanation of the procedure, including the characteristics used for identification, tools used and an analysis of observed properties, indicating a successful strategy for investigation. The student did not need to use a key.
Note: This is classified as Expert primarily due to the detail included with the drawing, the scientific vocabulary used in explanations, and the procedural description in the conclusions.