8.3.1.3 Rocks
Interpret successive layers of sedimentary rocks and their fossils to infer relative ages of rock sequences, past geologic events, changes in environmental conditions, and the appearance and extinction of life forms.
Classify and identify rocks and minerals using characteristics including, but not limited to, density, hardness and streak for minerals; and texture and composition for rocks.
Relate rock composition and texture to physical conditions at the time of formation of igneous, sedimentary and metamorphic rock.
Overview
MN Standard in Lay Terms
Rocks tell stories. The conditions at the time rocks and minerals form are recorded in the rock. In the case of igneous rocks, the mineral composition and mineral grain size are clues to the type of magma and the rate of cooling. Sedimentary rocks hold clues about the environment the sediments were deposited in, the types of living organisms that existed at that time, geologic events that occurred, and can be used to determine relative ages of rock layers. Metamorphic rocks may hold clues to the types of rock that was in an area prior to the events that caused them to change, and help to tell the story of the geologic events in an area.
Big Idea
Processes that shape the earth, including elements of the rock cycle occur the same way now as they did in the past. Using this knowledge, it is possible to make inferences about geologic history by making observations of rocks and rock formations today.
MN Standard Benchmarks
8.3.1.3.1 Interpret successive layers of sedimentary rocks and their fossils to infer relative ages of rock sequences, past geologic events, changes in environmental conditions, and the appearance and extinction of life forms.
8.3.1.3.2 Classify and identify rocks and minerals using characteristics including, but not limited to, density, hardness and streak for minerals; and texture and composition for rocks.
8.3.1.3.3 Relate rock composition and texture to physical conditions at the time of formation of igneous, sedimentary and metamorphic rock.
The Essentials
"Rocks are records of events that took place at the time they formed. They are books. They have a different vocabulary, a different alphabet, but you learn how to read them."
-John McPhee
- NSES Standards:
Content Standard F (grades 5-8)
Lithospheric plates on the scales of continents and oceans constantly move at rates of centimeters per year in response to movements in the mantle. Major geological events, such as earthquakes, volcanic eruptions, and mountain building, result from these plate motions.
Land forms are the result of a combination of constructive and destructive forces. Constructive forces include crustal deformation, volcanic eruption, and deposition of sediment, while destructive forces include weathering and erosion.
Some changes in the solid earth can be described as the "rock cycle." Old rocks at the earth's surface weather, forming sediments that are buried, then compacted, heated, and often recrystallized into new rock. Eventually, those new rocks may be brought to the surface by the forces that drive plate motions, and the rock cycle continues.
Water is a solvent. As it passes through the water cycle it dissolves minerals and gases and carries them to the oceans.
Living organisms have played many roles in the earth system, including affecting the composition of the atmosphere, producing some types of rocks, and contributing to the weathering of rocks.
Content Standard C (grades 5-8)
The earth processes we see today, including erosion, movement of lithospheric plates, and changes in atmospheric composition, are similar to those that occurred in the past. Earth history is also influenced by occasional catastrophes, such as the impact of an asteroid or comet.
Fossils provide important evidence of how life and environmental conditions have changed.
- AAAS Atlas:
The Physical Setting: Changes in the Earth's Surface
Benchmarks of Science Literacy
Chapter 4C: By the end of the 8th grade, students should know that
Sediments of sand and smaller particles (sometimes containing the remains of organisms) are gradually buried and are cemented together by dissolved minerals to form solid rock again. 4C/M3
Sedimentary rock buried deep enough may be re-formed by pressure and heat, perhaps melting and recrystallizing into different kinds of rock. These re-formed rock layers may be forced up again to become land surface and even mountains. Subsequently, this new rock too will erode. Rock bears evidence of the minerals, temperatures, and forces that created it. 4C/M4
Thousands of layers of sedimentary rock confirm the long history of the changing surface of the earth and the changing life forms whose remains are found in successive layers. The youngest layers are not always found on top, because of folding, breaking, and uplift of layers. 4C/M5
There are worldwide patterns to major geological events (such as earthquakes, volcanic eruptions, and mountain building) that coincide with plate boundaries. 4C/M13** (BSL)
Chapter 4D: By the end of the 8th grade, students should know that
All matter is made up of atoms, which are far too small to see directly through a microscope. 4D/M1a
The atoms of any element are like other atoms of the same element, but are different from the atoms of other elements. 4D/M1b*
Atoms may link together in well-defined molecules, or may be packed together in crystal patterns. Different arrangements of atoms into groups compose all substances and determine the characteristic properties of substances. 4D/M1cd*
Equal volumes of different materials usually have different masses. 4D/M2*
In solids, the atoms or molecules are closely locked in position and can only vibrate. In liquids, they have higher energy, are more loosely connected, and can slide past one another; some molecules may get enough energy to escape into a gas. In gases, the atoms or molecules have still more energy and are free of one another except during occasional collisions. 4D/M3cd
The temperature and acidity of a solution influence reaction rates. Many substances dissolve in water, which may greatly facilitate reactions between them. 4D/M4
No matter how substances within a closed system interact with one another, or how they combine or break apart, the total mass of the system remains the same. 4D/M7a*
Most substances can exist as a solid, liquid, or gas depending on temperature. 4D/M8** (SFAA)
A substance has characteristic properties such as density, a boiling point, and solubility, all of which are independent of the amount of the substance and can be used to identify it. 4D/M10** (NSES)
Misconceptions
- Any crystal that scratches glass is a diamond.
- Rocks must be heavy
- Rocks (and minerals) grow.
- Coarse-grained rocks are rough, fine-grained rocks are smooth
- One thing that students may not realize is that rocks go through a cycle where many things change the rock, ultimately "recycling" it.
- They also may believe that rocks can only change into one other type of rock, when they can actually change into any other type of rock.
- Heat can change a rock, but students often equate temperature and heat, not realizing that there is a difference. Just because a rock is heated does not mean that the temperature will continue to increase. This comes into play when talking about igneous and metamorphic rocks.
- Students may not know that a rock cycle takes millions of years to complete.
- The earth was always as it is now, or that any changes that have occurred must have been sudden and comprehensive
- Soil is the precursor of rocks. It changes from soil to clay to rock.
- Minerals are the same as rocks only they are precious rocks.
Vignette
Vignette ES 5-8: Properties of rocks & minerals
This vignette illustrates students learning about the stories that properties of rocks and sediments tell us about the earth. Important knowledge gained includes awareness of different types of sediment or rocks in different natural environments. Important science skills practiced include sample collecting, observation and recording, experimentation, interpretation of observations and experiments, and use of past interpretations to reach new conclusions. The vignette illustrates a variety of teaching techniques allowing students to learn from their own activity, learn from hearing and discussion, and learn through observation.
As part of an extensive study of their natural environment, Mr. B's students spend time learning about connections between sediment, rocks, and the environment, and thinking about how environments have changed in the past. Each student brings one or two samples of sediment ("dirt") to class, taking care to describe exactly the location where they collected his/her sample. Stu- dents involve their families or other adults in the collection of sediment as they explore streams, ponds, lake shores, lake bottoms, bogs or marshes, steep hills, flat fields, or other environments near their home.
They are told to avoid places that contain indistinct sediments, such as their yard, or places that are not related to the natural environment, such as a sandbox. Students describe each sample, recording its appearance, odor, texture, and any characteristics they notice such as sand (How big are the particles?) or remains of living things (What kinds of living things?). They record their observations with pictures and words, taking care to label each description. Students then use their records in an "identification game" in which each team tries to recognize sediments after they have been scrambled, using only their memories and their records of each sample.
Later, after students have become comfortable with how the samples are different, they begin to think about why they are different. Students talk about and try to determine the environments different samples come from. After discussion, students work in groups to construct a lake and lake shore in a plastic basin, using a mixture of fine dirt, sand, and gravel.
They use their hand to make small waves that lap against the shoreline and record their observations: how the slope of the sand changes at the shoreline, where the shoreline is steeper, where it is less steep, and the way sediment is accumulated and distributed at the shoreline and further out in the lake over time. They speculate on how the different parts of the original sediment become separated.
After the students have become familiar with sediments, Mr. B distributes samples of a fossil trilobite in shale and a fossil worm burrow in sandstone. Students are helped to see that the sandstone is made of little sand grains stuck together. Scraping the shale with a knife, Mr. B shows them the fine powder that results and the students describe it as a rock made of mud. Since the students studied insects in an earlier science activity, Mr. B has them draw pictures of the trilobite and describe to each other how it is like an insect and how it is different from an insect. Then the students draw a picture of the trilobite in the environment in which it died, including other animals, plants, or features that they think may have been there. What kind of place was it? Was it a beach? A river? They also draw a picture of the environment where the worm which made the burrow lived. Was it in the same place as the trilobite? Could it have been close by?
From SciMathMN K-12 Science Frameworks 3-123
Resources
Suggested Labs and Activities
An explanation of geologic time from the Museum of Paleontology at Berkeley, including the difference between relative dating and absolute dating. Very easy to understand using familiar examples to lead to the geologic ideas. (8.3.1.3.1.)
Also from Berkeley, this activity reinforces the concepts of relative dating and includes index fossils. (8.3.1.3.1.)
Minnesota rock and mineral resources: Mineral identification lab, using the properties of density, hardness, streak and luster. Rock identification lab using the characteristics of grain size, mineral composition, and texture. (8.3.1.3.2.)
This lesson "Every Pebble Tells A Story" would be a great formative assessment following a study of rocks as it requires that students to apply the ideas they have learned to interpret their observations of a rock sample of their choosing. (8.3.1.3.2, 8.3.1.3.3)
A common classroom activity to help understand crystal formation and growth is making rock candy. This page from the Exploratorium includes directions for making rock candy as well as information about crystal formation to help understand rocks and minerals. (8.3.1.3.3.)
While absolute dating is not a concept addressed in the 8th grade standards, students are often aware of it and want to know how it works. This is a simple activity that may help to clarify the idea. (8.3.1.3.1)
Instructional suggestions/options
"It is important for students at this age to understand how sedimentary rock is formed, including the embedding of plant and animal remains that leave a record of the appearance and disappearance of different species and the environment that existed at that time. The study of the Earth's history provides evidence abot the evolution of the Earth's features, including the distribution of land and sea, features of the crust such as mountains, and the populations of living organisms that existed at different times. Students should have opportunities to study a variety landforms, including mountains, and how they came to be. They should understand that the Earth has gone through many changes and that where oceans once existed, mountains may exist today. The theory of plate tectonics is introduced at this level.
Because students do not have direct contact with the phenomena of uplift and wearing down of mountains as well as the longterm nature of geologic processes, instruction and hands-on experiences should be descriptive. Detailed explanations should wait until late in middle school or high school. It is also important to note that vast intervals of geologic time are difficult to comprehend."
Bibliographic Citation: Keeley, P, Eberle, F, & Tugel, J. (2007). Uncovering student ideas in science: 25 more formative assessment probes. Arlington, VA: National Science Teachers
Additional resources
Free NSTA online interactive modules to increase teacher background knowledge and understanding of rocks, minerals and their formation.
Rocks: Environments of Formation
Earth Science World Image Bank is a collection of high quality, high resolution photographs related to a variety of science topics. The mineral images may be useful as many classrooms do not have samples of a wide variety of minerals and crystals. (8.3.1.3.2.)
"Earth Revealed" is a series presented by the Annenberg Foundation in half hour videos covering a variety of earth science topics. These videos may be used to increase background knowledge of teachers or shown to students as part of the lesson. (8.3.1.3.1, 8.3.1.3.2, 8.3.1.3.3)
This resource from the Mineralogical Society of America is not flashy, but is a good resource for reliable basic information. There is a dichotomous key for basic rock identification that may be useful, as well as descriptions of common rocks and minerals. (8.3.1.3.2, 8.3.1.3.3.)
The Minnesota Geological Survey publication "Common Minnesota Rocks," includes descriptions of the common rocks, as well as explanations of their formation. Additionally, it puts the formation of the different rocks into a timeline which explains the basics of Minnesota's geologic history. (8.3.1.3.1, 8.3.1.3.2, 8.3.1.3.3)
This website has a very nice basic overview of the properties of minerals as well as some information about different types of rocks. There are pictures along with the explanations. Although there is some information beyond the scope of the standard, the information is written at a level that should be accessible to students. (8.3.1.3.2.)
On this website there is an interesting and unique drawing that combines the rock cycle with plate tectonics into one diagram. (8.3.1.3.3. 8.3.1.1.3. 8.3.1.2.1.)
Digital Library of Earth Systems Education DLESE's educational resources include lesson plans, scientific data, visualizations, interactive computer models, and virtual field trips-in short, any web-accessible teaching or learning material.
Vocabulary/Glossary
- Cementation - the process by which naturally occurring cementing materials fill in the spaces between sediments forming sedimentary rock
- Composition - in rocks, the minerals or sediments that the rock is made up of
- cross cutting - a newer geologic feature going through an older structure; for example a volcanic intrusion running through sedimentary rock layers
- crystallization - the process by which minerals solidify with the molecules arranged in a repeating pattern (crystal structure)
- density - the amount of matter in a specific amount of space; mass/volume
- deposition - the dropping of materials moved by erosion in a new location
- erosion - the movement of loose earth materials from one location to another; agents of erosion include water, wind, ice, and gravity
- fossil - any remains, trace, or imprint of a plant or animal that has been preserved in the earth's crust since some past geologic or prehistoric time (Glossary of Geology, 4th edition, 1997)
- grain size - size of the mineral crystals in an igneous or metamorphic rock, or size of sediments as in a sedimentary rock
- hardness - a mineral's resistance to being scratched
- igneous - rock formed from molten rock that cools and hardens
- index fossils - fossils of organisms that existed for a limited time in a widespread area and can be used to identify the relative age of layers of sedimentary rock in which it is found
- luster - the way that light reflects off the surface of a mineral
- metamorphic - a rock (igneous, sedimentary, or metamorphic) that has undergone a physical and/or chemical change due to increased heat and/or pressure
- mineral - a natural occurring, inorganic solid with a definite composition and crystal structure
- original horizontality - sediments are initially deposited in horizontal layers with the newer sediments settling on top of the older sediments
- recrystallization - the change in a mineral's crystal structure/composition in response to stress (heat or pressure)
- relative age - comparative age of rock or fossil compared to other geologic features or rocks
- relative dating - the use of index fossils, the principle of original horizontality, cross-cutting features and other indicators to determine the order of past geologic events
- rock sequences/rock cross-section - a side-view of the rock in an area, showing layers, cross-cutting features, etc.
- Rock - Rocks are made of different kinds of minerals, or broken pieces of crystals, or broken pieces of rocks. Some rocks are made of the shells of once-living animals, or of compressed pieces of plants. Rocks are divided into three basic types, igneous, sedimentary and metamorphic, depending upon how they were formed.
- Sedimentary - rock made up of sediments that are either compressed or cemented together
- Streak - the color of the powder of a mineral
- Superposition - layers that are closer to the surface are younger than layers that are lower in rock or sediment that is has not been disturbed since deposition
- texture - refers to the grain size that the rock is composed of; generally coarse or fine
The USGS Rocks and Minerals education site. The content on this site is written at a level that should be easily understood by most 8th grade students. This site could be used independently by students or used to supplement classroom instruction. Includes an age-appropriate glossary of geology terms. (8.3.1.3.2, 8.3.1.3.3.)
Fossils and Time presented by the USGS. This site could be used independently by students or as an additional resource for classroom presentation. (8.3.1.3.1.)
The AMNH presents this information based on their Fossil Hall. The timeline includes drawings of the organisms that lived the time periods represented with descriptions of the environments that the organisms lived in. (8.3.1.3.1, 8.3.1.3.3.)
While many earth science classrooms have a variety of rock samples for students to observe and identify, they may not have some of those that are specific to Minnesota. The Minnesota Geological Survey "Virtual Egg Carton" includes these rocks, as well as maps of where they are found and information about how they formed. (8.3.1.3.2, 8.3.1.3.3.)
Assessment
Assessment of Students
Bibliographic Citation: Keeley, P, Eberle, F, & Farrin, L. (2005). Uncovering student ideas in science: 25 formative assessment probes. Arlington, VA: National Science Teachers Association.
"Cookie Crumbles" asks students to decide how the weight of a whole cookie compares to the cookie broken into pieces and crumbs. It elicits ideas about conservation of matter. Though not directly related, ideas about conservation of matter of ordinary objects will affect students' understanding of weathering of rocks and the rock cycle.
"Beach Sand" asks students to explain the origin of sand on a beach. It elicits student ideas about weathering, erosion, deposition, and landforms.
Bibliographic Citation: Keeley, P, Eberle, F, & Tugel, J. (2007). Uncovering student ideas in science: 25 more formative assessment probes. Arlington, VA: National Science Teachers Association.
"Is it a Rock? (version 1)" asks students to decide whether a number of objects are rocks or not. It elicits student ideas about whether rocks come in many sizes and shapes, as well as their understanding of words such as boulder, gravel, and sand.
"Is it a Rock? (version 2)" asks students to decide whether a number of objects are rocks or not. It is designed to determine if students can differentiate between human-made, "rock-like" materials and geologically formed rocks (even ones shaped by humans).
Assessment of Teachers
Questions could be used as self-reflection or in professional development sessions.
- How have the economic fortunes of MN been tied to rocks and minerals?
- Where does all that rock and concrete used to build a highway come from?
- How much does it cost to build 1 mile of new road or freeway?
Differentiation
According to Lee & Buxton (2010), a couple of approaches are useful for assisting English Language Learners (ELLs): teach content while fostering language development and draw on the so-called "funds of knowledge", which are students' personal experiences from home or community. For additional details on this see the original NSTA News posting and the official NSTA position statement.
Lee, O., & Buxton, C.A. (2010, April). NSTA Report: Teaching science to English language learners.
English Language Learners. Official NSTA Position Statement.
In much of Minnesota, the surface is covered with sediments deposited by departing glaciers. Different glacial advances left different sediments based on where the sediments that were imbedded in the ice had been removed from. Using the ability to identify different rocks, students might be encouraged to do some sampling of glacial sediments and see if they can learn about where those sediments originated.
The website has many for specific classroom suggestions for SpEd, ELL
Students with disabilities. Official NSTA Position Statement.
There are many opportunities for students to write and record their own observations when studying rocks and minerals.
Many aspects of this standard are hands-on, such as the various tests done to determine an unknown mineral.
Books and other resources addressing rocks and minerals are available at all reading levels and various depths of understanding. With the assistance of the school librarian, it should be possible to have a wide range of materials available for student use in the classroom during a rocks and minerals unit.
Parents/Admin
Administrators
During units addressing these standards observers would see a variety of rock samples available for students. Students would be using streak plates and hardness kits to explore the properties of minerals and then use those skills to identify unknown minerals. Students might be using a variety of resources to increase their understanding of the formation of rocks and how the properties of the rocks are clues to how they formed. This might include online resources, models, diagrams and books. Using fossils and perhaps studying a location like the Grand Canyon or the Badlands of North Dakota, students would be learning about layers of sediments and how those fossils can be used to understand the relative age of the rock layer.
Since rocks are found everywhere, in all settings, students can find samples of rock to "read" to their families. Whether on buildings, walls, driveways or in natural settings, students can try to identify what type of rock they are seeing and to determine anything about its natural history.