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Middle Grades Science Textbooks: A Benchmarks-Based Evaluation

SciencePlus: Technology and Society. Holt, Rinehart & Winston, 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. This idea is presented most explicitly in the Niagara Falls story in grade six (Level Green, pp. 474–477s). The text notes that Niagara Falls is considered to be young (only 12,000 years old), and that it has changed over time. Students are to compare a sketch of the falls in 1678 to a current photograph, and are asked how the Falls will change in the future. Later, in the same chapter, an activity has students find a local feature in their neighborhood (such as a crack in a rock or a spot of bare ground) that seems to show a change taking place and asks them to attempt to document the change (p. 479s). Students may sketch or photograph the feature periodically as well as describe in their notebooks the changes they see. Also, they are asked to compare the feature at the beginning of this investigation to how it looks throughout, and answer such questions as, “Will the change continue to take place?” (p. 479s).

For this key idea, there are also several practice questions, such as having students write how their neighborhoods have changed in the last 300 years and how they think the neighborhoods will change in the next 300 years (p. 476t). In addition, students are also asked to perform skits “portraying a series of people who see changes in a local landform over time” (p. 480t).

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

There is a content match. SciencePlus presents several processes that change the surface of the Earth. The sixth-grade text describes the processes of weathering and erosion (due to gravity, water, wind, and ice) and explains how plate interactions cause changes in the Earth (Level Green, pp. 470-519s). The seventh-grade text also presents information about volcanoes and earthquakes (Level Red, pp. 362-377s). However, these text descriptions focus mainly on the mechanics of the processes, presenting little information on how each process changes the landscape. A notable exception is the sixth-grade story of Niagara Falls (Level Green, pp. 474-477s). A diagram shows how the falling water erodes softer layers of rock from beneath hard layers (which shows the process of erosion), and how the location of the falls has changed over time (which shows the change in the surface of the Earth).

The material provides several opportunities for students to practice using this key idea, such as making a display showing how weathering has affected their schoolyard (Level Green, p. 485t), writing a paragraph about down-slope movements (Level Green, p. 490s), and writing a story or drawing a picture of the formation of a volcano (Level Red, p. 380s).

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. This idea is stated in the sixth-grade text: "Hutton believed that Earth processes at work today have also been at work throughout time and that the evidence of this could be seen in the rocks around us" (Level Green, p. 474s). However, no examples, phenomena, or practice questions are provided.

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. Although the text gives examples of abrupt and slow Earth-changing processes, it does not present a general statement or discussion of the time frames of these processes. Furthermore, the examples are presented in isolation from one another, as they appear in two different grade levels:
  • A landslide in Canada "broke loose without warning and plummeted into the valley below." [Level Green, p. 488s]
  • The location of Niagara Falls has changed over the last 300 years. The teacher's guide mentions that this is a relatively fast change on the surface of the Earth. [Level Green, p. 476st]
  • The volcano Paricutin grew 150 meters in six days and 410 meters in nine years. [Level Red, p. 375s]
  • The island of Surtsey formed from continuous volcanic eruptions over 3.5 years. [Level Red, p. 376s]
  • A discussion question suggested in the teacher's guide asks how long it took the Grand Canyon to form. [Level Green, p. 472t]

The text does not compare the time frames of the different examples presented, and no practice questions are provided for this idea.

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 neither states this key idea in general terms nor gives examples to illustrate it. Although two examples of very slow changes are provided, the gradual processes that created them are not discussed. Sixth-grade students are asked to speculate about how the Great Rift Valley of Africa will change in a few million years (Level Green, p. 464t) and how long it took the Grand Canyon to form (p. 473t). However, they are not expected to indicate that these features resulted from small, unnoticeable changes that accumulate over long times to make significant, visible changes on the Earth. In another instance, a gradual process is described but the long-term result is not. The student text discusses the impact of a single raindrop and explains that each raindrop strikes the Earth with "enough force to break off tiny fragments from solid rock" (p. 495s). Unfortunately, the text does not further explain that such small changes can accumulate over very long times to cause significant changes in the Earth's surface.

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. The text for sixth-grade mentions several types of evidence for a single vast continent (Pangaea):
  • [T]he discovery of fossils of a small lizard called Mesosaurus that were found only in eastern South America and southwestern Africa. [Level Green, p. 459s]
  • [M]atching coastlines, coal found in Antarctica, and identical rock formations and similar fossils found in South America and Africa. [pp. 460-461s]

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. After describing Wegener's hypothesis, the sixth-grade text explains that, "During the 1950s and 1960s, new techniques provided new evidence and scientists began to theorize that the Earth's crust is composed of a number of huge plates, moving in various directions" (Level Green, p. 461s).  Several diagrams show the location and direction of movement of the Earth's plates (e.g., pp. 464s, 465s, and 468s). The seventh-grade text revisits the idea by showing another diagram of moving plate boundaries and asking students, "When the plates do move, what happens to the boundaries of the plates?" (Level Red, p. 358s). The same text also uses the idea of plate tectonics to explain the locations of earthquakes (p. 368t, question A) and volcanoes (p. 377t, question F). Other questions focus on this idea, such as, "What would the Earth's surface be like if there were 20 smaller crustal plates instead of the existing major ones?" (p. 359t).

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 first presents this idea in grade six and revisits it in grade seven. The sixth-grade text describes what can happen when moving plates interact with one another: "As the plates move, they interact with one another at their boundaries. There are three basic types of plate boundaries: where plates are separating, where they are converging (approaching each other), and where they are sliding past each other" (Level Green, p. 464s). An accompanying diagram illustrates how landforms result from these plate motions (p. 464s). Students are asked to apply the idea of moving plates to explain how the Hawaiian Islands formed (p. 468st, question 1). The seventh-grade text also describes the theory of plate tectonics (Level Red, pp. 358-359s) and then asks students to apply the idea to explain various rock formations (p. 360s). Students are asked to model fault formation (pp. 361s, 363-365s) and relate earthquakes to plate boundaries (p. 368st, question A). Then they are to read about volcanoes (pp. 370-376s) and relate them to plate boundaries (p. 377st, question F).

Building a Case

SciencePlus does not attempt to build a case for any of the key Earth science ideas. Rather, the text asserts the ideas and provides activities to illustrate them. When evidence for the ideas is provided, it is not presented completely enough for students to appreciate it. For example, the text provides some evidence for the 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). The text mentions the "similarities of coastlines on each side of the Atlantic" and that "identical rock formations have been found in Africa and South America" (Level Green, p. 460s), but does not explain the significance of this evidence. Without understanding the slow process of sedimentation, students are not likely to understand why "identical rock formations" are a significant piece of evidence in favor of moving continents. Similarly, the text notes that, "Mesosaurus has been found in only two places in the world, Africa and South America" (Level Green, p. 460s), but fails to point out that it is very unlikely for organisms to develop in exactly the same way in separate environments. Without this argument, the fossil evidence may not be convincing.


SciencePlus presents most of the key Earth science ideas. The idea that the Earth is changing continually (Idea a) is presented in its entirety, as are ideas about how the Earth has changed (Ideas b, g, h). However, ideas that relate to the time frames of changes to the Earth's surface (Ideas d, e) are not addressed or are addressed in isolated instances, and no generalization is provided. Thus the material presents an incomplete story of the processes that shape the Earth's surface. Given the vastness of time scales over which some of these changes have occurred, the inattention to time frames may undermine the plausibility of the other key ideas.

Even when key ideas are treated, the examples provided are not tied together and related to the generalization. For example, although several specific processes that shape the Earth are presented (such as streams, glaciers, wind, mountain building, volcanic eruptions, and earthquakes), there are no statements, questions, or activities that focus students on the general idea that several processes act to change the surface of the Earth. This idea is not further developed to explain that several of these processes can act at the same time or that opposing processes can act on the same landform.

The material makes few, if any, relevant connections to other ideas that could strengthen the key Earth science ideas. For example, although the material includes several activities that rely on the use of models to show Earth processes, it misses the opportunity to connect students' use of models to the role of models in science.

Beyond Literacy

SciencePlus takes particular care to avoid topics that are beyond what is needed for science literacy as recommended by Benchmarks for Science Literacy (American Association for the Advancement of Science, 1993) and National Science Education Standards (National Research Council, 1996). In a very few places, extraneous topics and terms are included, such as the elastic rebound theory (Level Red, p. 364s) and the types of volcanoes (Level Red, pp. 374-375s).


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.