August 31, 2005

Background Information

Mid-ocean ridges are major geologic features that all students have not physically seen or experienced. However, these ridges are some of the most dynamic and pronounced geologic features on earth that affect many parts of the earth system. Therefore, it is best to initiate this chapter with a concepts and ideas that students are relatively familiar with in their lives. One might think the bottom of the ocean floor is flat and void of life. However, this is not the case along mid ocean ridges. Beginning the unit by initiating what they already know about their environment would be the best way for students to build and construct their own knowledge regarding ridges.

Grade Level:

9-16

Learning Goals

After completing this chapter, students will be able to:

• Interpret, analyze, and synthesize data using data collected by scientists via a mapping application called GeoMapApp.
• Make inferences and conclusions that will lead students to understand that the ridges are symmetrical and are youngest near the spreading center.
• Comparing and contrasting slow, intermediate, and fast ridge systems and their implications on the environment.

Learning Rationale:

As stated earlier, plate tectonics is the most fundamental concept within the earth system because nearly all geologic process can be explained by this theory. The creation of the ocean crust along mid-ocean ridges may be described as the beginning of this very important cycle of creation of ocean crust that are usually subducted and destroyed along the opposite ends of plate boundaries. This chapter is not designed to completely explain the theory of plate tectonics; however it is probably best to use this chapter after students have a basic understanding about the dynamics that occur along plate boundaries. Through inductive reasoning, students will "discover" the dynamic process that occurs along a diverging plate boundary or spreading centers along mid-ocean ridges. Students then will be able to make logical inferences and conclusions based upon this process from the data they collected. By students constructing their own understanding mid-ocean ridges, they will be able to understand that geologic processes that occur are part of a much larger earth system.

Instructional Strategies

1. Introduce this chapter by emphasizing that this is an authentic activity by introducing the three RIDGE 2000 study sites and the data that is currently being collected here.
2. Provide students with relief maps of the United States and a map of the Atlantic Ocean elicit what students already know about topographical profiles.
3. Within collaborative (data only) groups, have students investigate topographical profiles of mid-ocean ridges and spreading rates.
4. Analyze, synthesize and make inferences between slow, intermediate, and fast spreading centers
5. Have students disseminate their data and inferences to the class.

Learning Contexts

Developing a meaningful context that is meaningful for students that relates to mid-ocean ridges is challenging. However, identifying what students know initially may help developing this very important concept in geology and earth system education.

Science Standards

Abilities necessary to do scientific inquiry

12ASI1.3

Use technology and mathematics to improve investigations and communications. A variety of technologies, such as hand tools, measuring instruments, and calculators, should be an integral component of scientific investigations. The use of computers for the collection, analysis, and display of data is also a part of this standard. Mathematics plays an essential role in all aspects of an inquiry. For example, measurement is used for posing questions, formulas are used for developing explanations, and charts and graphs are used for communicating results.

12ASI1.5

Recognize and analyze alternative explanations and models. This aspect of the standard emphasizes the critical abilities of analyzing an argument by reviewing current scientific understanding, weighing the evidence, and examining the logic so as to decide which explanations and models are best. In other words, although there may be several plausible explanations, they do not all have equal weight. Students should be able to use scientific criteria to find the preferred explanations.

Energy in the earth system

12DESS1.1

Earth systems have internal and external sources of energy, both of which create heat. The sun is the major external source of energy. Two primary sources of internal energy are the decay of radioactive isotopes and the gravitational energy from the earth's original formation.

12DESS1.2

The outward transfer of earth's internal heat drives convection circulation in the mantle that propels the plates comprising earth's surface across the face of the globe.

The origin and evolution of the earth system

12DESS3.2

Geologic time can be estimated by observing rock sequences and using fossils to correlate the sequences at various locations. Current methods include using the known decay rates of radioactive isotopes present in rocks to measure the time since the rock was formed.

Geography Standards

Standard 7: The physical processes that shape the patterns of Earth's surface.

Standard 17: How to apply geography to interpret the past.

Time Required

6-8 class periods (45 minute class periods)

Other Resources

(for teacher)

Petrological Database of the Ocean Floor

Marine Geology and Geophysics

Isochrons

Other Resources (public) with descriptions

For Topographic Maps http://geology.asu.edu/~sreynolds/topo_gallery/topo_home.htm