Pre-assessment Report on the Rock Cycle

Eilisha Joy Bryson

University of Pennsylvania

EDU 536/631 – Teaching and Learning of Middle School Science

December 3, 2005

Part I: Background Information on the Rock Cycle

The topic of this pre-assessment report is the rock cycle, one component of Earth Science. This cycle is a key idea in understanding the history of the Earth in terms of how it took its form, and how it continues to change.

In the Integrated Science textbook, they defined rocks in a logical way. “Elements are chemically combined to make minerals. Minerals are physically combined to make rocks. A rock is defined as an aggregation of one or more minerals and perhaps other materials that have been brought together into a cohesive solid” (p. 280). There are three different types of rocks- igneous, sedimentary, and metamorphic- based on the different ways in which rocks are formed. Rocks are constantly changing, and they go through a cycle. The different processes that change a rock’s form are: erosion, heat, pressure, and cooling. How these processes actually change a rock is described further below.

The purpose of studying the rock cycle has to do with learning about the earth’s formation. The rocks reveal information about minerals and resources that are found in certain areas of the earth. By interpreting the structure of rocks, it can reveal information about the events in earth’s history. Knowing about the rock and rock structures also provides insight into how the earth came to look the way it does now, and how and why it changes.

All rocks, according to Integrated Science, were said to once have been igneous. The name igneous actually comes from the Latin word ignis, or fire, because igneous rocks begin as magma, “melted rock material” and become rock after the magma has cooled and solidified (p. 280). The following information is necessary because it explains how igneous rocks are formed, but it also explains how rocks are able to change from one type into another type. The magma that forms the igneous rock is actually made from rocks- any type of rock- metamorphic, sedimentary, or even igneous. It is important to understand this process because it illustrates how rocks can change, which is the whole basis of the rock cycle.

Inside the Restless Earth states that the magma that creates igneous rocks can form in three ways, all of which involve melting rock. Magma will form when rocks are heated to temperatures that cause some or all of the minerals within the rock to reach their melting points. The melting point of rocks can change when its chemical composition changes. This happens if other elements combine with the rock, and magma then forms. The final way magma forms is when rocks melt because they have less pressure on them. Higher levels of pressure, from being deep within the Earth, cause the minerals within rocks to remain as solids. When the rocks rise to fewer depths, the pressure is released and the minerals can melt, thereby forming magma.

Another rock that can form as rocks get recycled through the rock cycle is sedimentary rock. This type of rock is formed from dissolved, eroded pieces of metamorphic, igneous, other sedimentary rocks, or from dead sea creatures. Water ice, heat, and wind erode the elements and the pieces, or sediments, are carried away. The sediment forms on the Earth’s surface in layers, many of which are on the bottoms of seas. These fragments alone do not create rocks. In order for the sediment to join together two things must happen. The explanation of this is explained well in the Inside the Restless Earth textbook.

As new layers of sediment are deposited, they cover older layers. Older layers become compacted. Dissolved minerals, such as calcite and quartz, separate from water that passes through the sediment to form a natural cement that binds the rocks and mineral fragments together into sedimentary rock. (p. 40)

Once the bonding has occurred, the International Encyclopedia of Science and Technology, says that the Earth can move causing the sediments to “uplift … and tilt, fold, or fault” thereby creating the sedimentary rock (p.318). One distinguishing feature of sedimentary rock is its visible layers, or strata.

The last type of rock is metamorphic rock. It takes its name, as Inside the Restless Earth notes, from two Latin words, meta (meaning change) and morphos (meaning shape). A metamorphic rock is one that has changed its shape or chemical composition in a “distinctly different” way (Integrated Science, p. 282). Heat and pressure are the two factors that can cause such a change: heat and pressure. The heat comes from the magma, either through direct or indirect contact. Pressure can come from movements of the Earth. The heat and pressure interact with a pre-existing rock and alter its shape or mineral alignment. These behaviors are similar to those that cause rocks to melt into magma and cool into igneous rock, but they are slightly different. The pressure and heat are not enough to melt the rock, just change its solid form. This is the final way rock can change in the rock cycle.

The International Encyclopedia of Science and Technology and Inside the Restless Earth note that there are two important characteristics that all rocks have. One is the texture of the rock. For igneous rocks, that is determined by the location and rate in which the magma cools. A rock’s texture is “coarse, medium, or fine-grained” (Inside the Restless Earth). Fine-grained igneous rocks, for example, will have small or no crystals. This happens when magma cools quickly on the Earth’s surface, not allowing enough time for crystals to form. Igneous rocks that are formed under the Earth’s surface, where temperatures are hotter, will cool at a slower rate. The large crystals will have time to take shape, causing the igneous rock to be coarser. The other characteristic is the chemical makeup of the rock, or its composition.

This topic was chosen from Inside the Restless Earth, which is the science textbook mandated for 8^th Grade students in the School District of Philadelphia. The rock cycle topic is one of the concepts of earth Science that the students have to study. In the National Science Education Standards, the rock cycle is listed under “Earth and Space Science”, Science Content D, which states that students should have knowledge of the “structure of the earth system”. The Standards also contain the following points about the rock cycle:

• Students can investigate the water and rock cycles as introductory examples of geophysical and geochemical cycles.
• Some changes within 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.

The Benchmarks said this about the rock cycle for grades 6 to 8:

· 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.

· Sedimentary rock buried deep enough may be reformed by pressure and heat, perhaps melting and re-crystallizing 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.

· 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.

Children do tend to have misconceptions about rocks and the rock cycle. Several resources revealed interesting thoughts that students have come to believe. The textbook, Inside the Restless Earth, stated several misconceptions that students have. 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. This is interesting because the website that is mentioned below states that children have problems rationalizing such a long period of time.

Other sources were able to shed further insight into other misconceptions students have about rocks. On LEARN, a website for teachers that aligns activities with the standards, they noted the misconceptions that students have about the National Science Education Standards. Students believe, “The earth was always as it is now, or that any changes that have occurred must have been sudden and comprehensive.” The following ideas are ones students believe about rocks, specifically:

Rocks are associated with heaviness. Small rock fragments are stones, not rocks (Ex: a small piece of pumice would not be considered a rock). Mountains are associated with high rocks. 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. 

The School District of Philadelphia’s Core Curriculum was another resource I used to identify further misconceptions the students might have. It stated that students might need additional clarification on the differences and similarities between rocks and minerals. Students use them as if they are synonyms, but further attention is needed to explain thate minerals make rocks.

Part II: Analysis of Pre-Assessment Results

The students who took this pre-assessment are from Meredith School, a public school in the School District of Philadelphia. These students are in my 8^th grade, self-contained classroom. The class is mixed with Caucasians- 9 girls and 6 boys, and African-Americans- 5 girls and 4 boys. The girls out number the boys 14 to 10. In terms of economic status, Meredith does not qualify to receive free lunches for the entire school, and most students either do not qualify or never fill out the paperwork to receive free lunch. The school, as a whole has made adequate yearly progress, and is often commended for high standardized testing results. All but two students in my class are reading on grade level. Despite this, students are not receiving straight A’s in my class. The students are well behaved, but are still pre-adolescents.

The questions I chose for my pre-assessment were based upon the standards and upon several of the misconceptions students have. The questions were connected to the rock cycle, and are restated exactly in the next section of the paper. I will give a brief description of the questions here so that the rationale can be understood. For the first question, students had to fill in a blank rock cycle diagram with the processes that explain how one type of rock changes into another type of rock. On the second question, the students had to tell as much as they could about each step of the rock cycle. These addressed students’ knowledge of the processes or causes that make a rock change its form. I wanted to see if students would be able to describe where rocks come from, and to see if they had explanations of what happens to make a rock change its form. Finally, I asked the students to tell how long it takes a rock to change shape. This addressed the misconception that students do not have the right idea about how long it takes a rock to complete the rock cycle. The question connects with a misconception.

The students’ responses were very eye opening. I was surprised to read what the students believed once they had the opportunity to write their thoughts. The first question gave the most varied responses:

Look at the diagram above. It shows how one type of rock can be recycled into another type of rock. Use the processes from the list below and insert them into the diagram to help explain how the rock can be changed from one form into the other.

weathering, erosion, heat

pressure, melting, cooling

I actually gave two types of diagrams to the students, to see how the students responded to each one. One has plain arrows to connect one rock to the others. The second version had arrows that showed broken rock and shading. I wanted to see if the more descriptive arrows led students to complete the chart differently, and it did. To analyze the responses, I recorded all the processes students listed for each arrow.

Rock to rock	Correct answer	Students’ Responses from the plain arrows	Students’ Responses from the detailed arrows	Total student’s Reponses
From igneous to sedimentary	Weathering and erosion	Pressure– 1 Heat– 1 Erosion– 4 Weathering- 3 Melting- 1 Cooling- 0	Pressure– 8 Heat– 0 Erosion– 1 Weathering- 1 Melting- 0 Cooling- 0	Pressure– 9 Heat– 1 Erosion– 6 Weathering- 4 Melting- 1 Cooling- 0
From sedimentary to metamorphic	Heat and pressure	Pressure– 3 Heat– 2 Erosion– 2 Weathering- 3 Melting- 0 Cooling- 0	Pressure– 3 Heat– 0 Erosion– 5 Weathering- 2 Melting- 0 Cooling- 1	Pressure– 6 Heat– 2 Erosion– 7 Weathering- 5 Melting- 0 Cooling- 1
From metamorphic to sedimentary	Weathering and erosion	Pressure– 3 Heat– 0 Erosion– 2 Weathering- 2 Melting- 0 Cooling- 0	Pressure– 1 Heat– 0 Erosion– 0 Weathering- 3 Melting- 0 Cooling- 0	Pressure– 4 Heat– 0 Erosion– 2 Weathering- 5 Melting- 0 Cooling- 0
From metamorphic to magma	melting	Pressure– 3 Heat– 3 Erosion– 1 Weathering- 3 Melting- 8 Cooling- 0	Pressure– 0 Heat– 8 Erosion– 0 Weathering- 0 Melting- 5 Cooling- 0	Pressure– 3 Heat– 10 Erosion– 1 Weathering- 3 Melting- 13 Cooling- 0
From magma to igneous	cooling	Pressure– 1 Heat– 0 Erosion– 0 Weathering- 0 Melting- 0 Cooling- 9	Pressure– 0 Heat– 0 Erosion– 1 Weathering- 0 Melting- 0 Cooling- 10	Pressure– 1 Heat– 0 Erosion– 1 Weathering- 0 Melting- 0 Cooling- 19

The students’ responses showed me that they were unsure about the correct answers, but interestingly enough, they were able to rely on their background information to realize that magma was connected with heating, melting and cooling. The difference in responses based on the detailed arrows or the plain arrows was not that great except in one area, from igneous to sedimentary. The students who had the detailed arrows were able to see small pieces of rock and most of the students answered that it was pressure that broke that must have broken the igneous rock into those pieces. The students with plain arrows gave a variety of answers since they did not get any clues from the drawings. The students were most accurate in deciding that cooling was the correct process to turn magma into igneous rock.

The next question gave students a chance to share their thoughts on how the rock goes through the rock cycle.

In the space below, tell as much as you can to describe in more detail what happens in each step of the rock changing process.

Students’ responses were not detailed enough to show that any one student had a complete explanation for the processes rocks go through in the rock cycle. I recorded some phrases that students wrote; this gives insight into their understanding.

Mud turns into rock, then before you know it’s a rock!

Erosion turns rocks from big to small

Rocks go from solids to gooey stuff by erosion and weathering

Pressure comes from erosion and weathering

Rock cools after being in a volcano (2 students wrote this)

Pressure comes from tornadoes and hurricanes

Rocks can’t go from one form to the other

Pressure is created when rocks get stuck under big rocks or under streams

The winter cools rocks

Erosion is water and rocks banging against other rocks

The outer core heats metamorphic rock.

Sedimentary rocks are chipped off a pile or mountain.

Igneous breaks into little sediments because of pressure.

Erosion forms the shape of the rock.

The rocks’ texture, color, looks, or smell is changed.

Eight students did not give any additional explanation into the rock cycle. Their responses just restated the diagram they completed in sentence form instead of diagram form. Their responses reflected some of the misconceptions mentioned in the section above. One student showed greater understanding than any other. She said the following comments:

When the rain, snow, sleet, and hail gets to rock, it changes its texture. Another way is when wind chips away most of the rocks it gets eroded. Pressure can get put on a rock and chip it to make the smoothness different.

This student, the only student, actually explained the processes, giving ways things happen.

The final question asked,

How long do you think it takes for a rock to take form?

I grouped the responses in the following way. The correct answer is millions of years.

Possible response	# of Student Responses
A few days to 1 year	10
1 to hundreds of years	11
Thousands of years	1
1 million or more years	1

This activity and the analysis that accompanied it gave me insight into a new way to assess students. I have done pre-assessments before, but I never did them to discover what students’ misconceptions might be. It was an enlightening experience because I did not know that there was so much research about the topic. I also have never had to base my activities on the standards the way I had to with this task. I usually trusted the textbook, thinking, if it was in the book, then it must correspond with the standards. The most powerful thing that happened here, however, was the amount of information I learned. I did not know how to explain the rock cycle, but I was forced to do the research for the background information. I still have some questions, but my knowledge has increased drastically.

Based on the results my students gave, I see that I have some specific concepts to teach. The students did not explain an understanding of the processes of weathering, erosion, and pressure. They seemed to know that magma was hot, but they did not clearly understand that it was formed from melted metamorphic rock.

References

Inside the Restless Earth. Orlando: Holt, Rinehart & Winston.

Core Curriculum: Grade 8 Science. (2004). School District of Philadelphia. Philadelphia: Songhai Press.

Learn. http://www.nasalearn.org/teacher_support_alerts_misconceps_earthsci.htm

Luck, S. (Ed.) (1998). The International Encyclopedia of Science and Technology. New York: Oxford.

Tillery, B., Enger, E., & Ross, F. (2004). Integrated Science (Second Edition). Boston: McGraw Hill.

National Science Education Standards. Retrieved from http://www.nap.edu/readingroom/books/nces/html/6d.html

Benchmarks for Science Literacy (1993). Retrieved from http://www.project2061.org/publications/bsl/online/ch4/ch4.htm#Earth_6_8