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Middle Grades Science Textbooks: A Benchmarks-Based Evaluation

Science Insights. Addison-Wesley Publishing Company, 1996 and 1997
Earth Science Life Science Physical Science

About this Evaluation Report
Content Analysis
Instructional Analysis

[Explanation] This section examines whether the curriculum material's content aligns with the specific key ideas that have been selected for use in the analysis.
[Explanation] This section examines whether the curriculum material develops an evidence-based argument in support of the key ideas, including whether the case presented is valid, comprehensible, and convincing.
[Explanation] This section examines whether the curriculum material makes connections (1) among the key ideas, (2) between the key ideas and their prerequisites, and (3) between the key ideas and other, related ideas.
[Explanation] This section notes whether the curriculum material presents any information that is more advanced than the set of key ideas, looking particularly at whether the “beyond literacy” information interrupts the presentation of the grade-appropriate information.
[Explanation] This section notes whether the curriculum material presents any information that contains errors, misleading statements, or statements that may reinforce commonly held student misconceptions.


Idea a: The surface of the Earth is changing continually.
There is a content match. There are a few brief mentions that the surface of the Earth is changing continually. For instance, in a segment called “Changes on the Surface,” the text states: “Over the last 2,000 million years, the earth has continued to change. But unlike the changes that occurred in the earth’s early history, these changes have followed regular patterns. The same patterns continue today” (Chapter 4: Time and Change, p. 77s). In another chapter, teachers are told, “Remind students that most movement in the crust is relatively slow and constant” (p. 113t). In the context of wave erosion, according to the Student Edition, “Waves constantly change the shape of the shoreline” (Chapter 12: Forces of Erosion, p. 271s), and a related suggestion in the Teacher’s Edition says, “Ask students to imagine they are planning to sail along the U.S. Atlantic coastline. Have them explain why they would want a recent map of the coastline” (p. 272t). The suggested response is that, “The coastline is constantly changing because of erosion and deposition” (p. 272t).

Idea b: Several processes contribute to changing the Earth’s surface.

There is a content match. Although this idea is not stated in general terms, several examples of Earth-shaping processes are described, such as folding and faulting (Chapter 6: Movement of the Crust, pp. 112–118s), earthquakes (Chapter 7: Earthquakes and Volcanoes, pp. 140–141s), and volcanoes (Chapter 7: Earthquakes and Volcanoes, pp. 144–147s). For the most part, the descriptions of Earth-shaping processes do not focus on what the surface of the Earth looked like before the process, as compared to how it changed or what it looked like after the process. Furthermore, the processes that change the Earth are presented independently from one another, and no attempt is made to describe how they might work together to shape the surface of the Earth.

Idea c: The processes that shape the Earth today are similar to the processes that shaped the Earth in the past.

There is a content match. A feature called Historical Notebook provides a brief explanation of Hutton’s principle of uniformitarianism. The text states, “According to this principle, the laws of nature do not change over time. Thus, the same processes that shaped the earth in the past are still at work today” (p. 79s). However, this idea is not further explained and no examples are provided to illustrate it.

Idea d: Some of the processes are abrupt, such as earthquakes and volcanic eruptions, while some are slow, such as the movement of continents and erosion.

There is a content match. The text characterizes a few Earth-shaping processes as being slow. For example, the changes that rocks undergo are described as slow: “The rocks and rock layers that make up the earth’s crust undergo similar changes all the time. Usually the change is very, very slow. But it produces mountains, valleys, and other features that make the earth's varied topography” (p. 113s). In the same way, the slow rate of erosion is mentioned in the context of mountain building: “Mountains don’t last forever. After their uplift stops, weathering and erosion slowly reduce their elevation” (p. 127s). And, wave erosion is mentioned as depositing sediments “over a long period of time” (p. 272s). Quick events, such as earthquakes and some volcanic eruptions, are described as well. In a few locations, these events are described as abrupt or sudden (pp. 133s, 140s, 146s). However, the generalization that Earth-shaping processes can occur over very short or very long time frames is not stated explicitly.

Idea e: Slow but continuous processes can, over very long times, cause significant changes on the Earth’s surface.

There is not a content match. The text does not state this idea in general terms or give examples to illustrate it. Even though some processes are described as slow (mountain building, the motion of tectonic plates, and erosion), there is no indication that these are instances of small, almost unnoticeable changes that can accumulate over long periods of time.

Idea f: Matching coastlines and similarities in rocks and fossils suggest that today’s continents are separated parts of what was a single vast continent long ago.

There is a content match. Chapter 5, on plate tectonics, begins by describing observations of matching coastlines: “Many people who looked at the [early] maps noticed something interesting about the shapes of the continents. It seemed as if Africa and South America could fit together like pieces of a jigsaw puzzle…” (p. 91s). The text then presents Wegener’s theory of continental drift and maps of the estimated past locations of the supercontinent and the subsequent major continents (pp. 91–92s). The text also describes the evidence from fossils, rock layers, and ancient glaciers, and indicates that the evidence supports the idea that there was once a single continent. For example:
Paleontologists found fossils of an ancient fernlike plant called Glossopteris in South America, Africa, India, Australia, and Antarctica. The seeds of Glossopteris are too heavy to have blown across oceans by wind. Scientists infer from this evidence that all these continents were connected at one time. [p. 93s]

Idea g: The solid crust of the Earth consists of separate plates that move very slowly, pressing against and sliding past one another in some places, pulling apart in other places.

There is a content match. This idea is presented in chapter 5. The text explains that “the entire lithosphere of the earth is divided into pieces called plates. The plates are constantly moving, each at a different rate and direction” (p. 98s). Also, the types of plate interactions are described: “Three kinds of interactions are possible at plate boundaries. Plates can move away from each other, they can collide, and they can slide past each other” (p. 100s). These three types of plate interactions are further described in text and diagrams (pp. 100–101s).

Idea h: Landforms and major geologic events, such as earthquakes, volcanic eruptions, and mountain building, result from these plate motions.

There is a content match. The text mentions many examples of the landforms and geologic events that result from the motion and interaction of the Earth’s plates. For instance, the Aleutian Islands, the San Andreas Fault, the Himalayan Mountains, and the Marianas Trench are explained as having resulted from plate interactions (pp. 102–103s). Several practice questions focus on categorizing the plate interactions or defining the three types of interactions. One practice question asks students to suggest how the Ural Mountains may have formed (p. 110st, Check Your Understanding, item 6).

Building a Case

Science Insights: Exploring Earth and Space asserts most of the key Earth science ideas and provides some activities to illustrate them but does not provide an evidence-based case for them. However, the text makes some attempt to build a case for the key idea that matching coastlines and similarities in rocks and fossils suggest that today’s continents are separated parts of what was a single vast continent long ago (Idea f).

This key idea states the evidence (matching coastlines, similarities in rocks, similarities in fossils) and the conclusion drawn from it (today’s continents are separated parts of what was a single vast continent long ago). Sometimes the text provides an argument that explains why the evidence supports the conclusion. For example, after stating that Glossopteris fossils were found on several now widely separated continents, the text points out that the seeds are too large to have been carried by the wind. This refutes one alternative explanation before stating the conclusion that “Scientists infer from this evidence that all these continents were connected at one time” (p. 93s). However, the text does not explain why finding the same fossil in now quite different climates requires an explanation. Given that fossils typically are found where organisms once lived, it is likely that these locations once had the same climate. While it is possible that widely separated regions could have the same climate, the most plausible explanation for this (and other) evidence is that the regions were once in close proximity. In another instance, the text presents an argument and the conclusion but fails to adequately describe the evidence: “Rocks found in parts of South America, Africa, India and Australia all show evidence of glaciers at the end of the Paleozoic Era. For these places to have glaciers, they had to be closer to the South Pole” (p. 94s).

The text does not describe how the rocks showed evidence of glaciers. Furthermore, essential background information about sedimentation, folding mountains and glacial features are not presented until later in the textbook (sedimentation in chapter 10, mountain building processes in chapter 6, and glaciers in chapter 12). Therefore, many pieces of evidence presented—such as, “On both continents, for example, there are mountain ranges formed by folding of the crust” and “the rocks also show the direction in which the glaciers traveled” (p. 94s)—are not likely to make sense to students. Although some of the evidence for an ancient supercontinent is presented, students are not likely to understand the significance of the evidence.


Science Insights: Exploring Earth and Space presents most of the key ideas in six chapters (4, 5, 6, 7, 11, and 12). Very little attention is given to the time frames of Earth-changing processes (Idea d), and that the surface of the Earth is constantly changing (Idea a). The idea that small, seemingly unnoticeable changes can accumulate over long time frames to create significant features on the Earth (Idea e) is not mentioned at all. Thus, this textbook presents an incomplete story of how the surface of the Earth changes.

Although experiences and examples of several of the key ideas are provided, there is almost no attempt to tie together all the experiences provided for individual key ideas. For example, discussion of the many processes that shape the Earth (streams, glaciers, wind, mountain building, volcanoes, and earthquakes) is distributed among several chapters, but there are no statements, questions, or activities that convey to students the fact that several of these processes often act at the same time on the same land feature.

Beyond Literacy

Science Insights: Exploring Earth and Space includes only a few topics that are beyond science literacy, such as, the magnetic data used as evidence for seafloor spreading (p. 97s) and convection in the mantle (p. 106s).


The evaluation teams developed a summary assessment of the most common kinds of errors found in each of the three subject areas—physical science, Earth science, and life science. In this context, “errors” is taken to mean not only outright inaccuracies, but also those instances in which the material is very likely to lead to or support student misconceptions. Overall, inducement to misconstrue is the most serious problem of accuracy in the evaluated materials.

The evaluation teams’ collective findings, presented below, should be taken as having general applicability to all of the evaluated materials, not complete and specific applicability in toto to any one of them.

Identified errors occur most frequently in drawings and other diagrams. They take the form of representations that are likely to either give rise to or reinforce misconceptions commonly held by students. Following are Earth science examples of the kinds of misleading illustrative materials of most concern to the evaluation teams:

  • Maps that do not show the accurate locations of earthquakes and volcanoes will prevent students from understanding the relationship between these events and plate boundaries. Likewise, diagrams and maps that do not include legends, and photographs that do not explain the size and scale of the object seen, are difficult for students to understand.

  • Diagrams that (a) depict plates moving away from one another, thus exposing the mantle, (b) show the mantle very close to the surface of the Earth, or (c) show plates as being a layer under the crust inaccurately represent the structure of the Earth and the motion of plates.

  • Diagrams that show the melting of subducted plates are incorrect. Subducting plates are known to cause melting in the mantle, and thus nearby volcanic activity, but the plates do not melt.