The different offsets observed across the Murray Fracture Zone from magnetic lineations (Fig. 4.1) are thought to be due to a change in location of the ridge crest to the south of the fracture zone about 40 Ma ago. The change in offset of anomalies of the same age implies a "ridge jump" of approximately 500 km to the east (Harrison & Sclater, 1972). Similar but better documented ridge jumps, which also greatly reduce the offset of crust of the same age on either side of a fracture zone, occur in the extreme south of the Atlantic Ocean (Barker, 1979). Here, to the south of the Falkland-Agulhas Fracture Zone, the ridge crest has jumped westward on three occasions since the opening of the South Atlantic, that is at 98, 63 and 59 Ma. In so doing it has reduced the original offset of 1400 km to approximately 200 km. Other ridge jumps, producing major changes in ridge crest geometry within the past 10 Ma, have occurred to the north of Iceland (Vogt et al., 1970) and along the crest of the East Pacific Rise in the east central Pacific (Herron, 1972).
In general, however, ridge jumps are relatively rare, as evidenced by the median position of oceanic ridges between separated continents. The geometry of ridge crest segments and transform faults is more likely to be modified, less dramatically, by ridge propagation (Section 6.11) and changes in the spreading direction (Section 5.9).
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Lets start by identifying what exactly certain boats are. Sometimes the terminology can get lost on beginners, so well look at some of the most common boats and what theyre called. These boats are exactly what the name implies. They are meant to be used for fishing. Most fishing boats are powered by outboard motors, and many also have a trolling motor mounted on the bow. Bass boats can be made of aluminium or fibreglass.