The rocks and topography of the sea floor are different from those on land. To understand the evidence for plate tectonics in the next chapter, you need to understand the nature of major sea-floor features such as mid-oceanic ridges, oceanic trenches, and fracture zones, as well as the surprisingly young age of the sea-floor rocks.
The material discussed in this chapter and the next are an excellent example of how the scientific method works. This chapter is concerned with the physical description of most sea-floor features - the data gathering part of the scientific method. The next chapter shows how the theory of plate tectonics explains the origin of many of these features. Geologists generally agree upon the descriptions of features but often disagree on their interpretations. As you read, keep a clear distinction in your mind between data and the hypotheses used to explain the data.
