White Paper Title: 
Why are mid-ocean ridges segmented? What time-scales apply to the different spatial scales of segmentation?

Mid-ocean ridge segmentation appears to correlate quite well with along-axis variations in axial depth, cross-axis morphology, basalt geochemistry, intensity of hydrothermal activity and abundance of benthic faunal communities on most spreading centers.  Thus understanding the origin of segmentation and its four-dimensional behavior is essential to understanding the linkages between a wide range of processes central to the mission of R2K.  Some ideas about why ridges are segmented:

1. Along-axis variations in melt supply?

2. Skewness of mantle upwelling relative to ridge strike?

3. Response of the ridge to migrating over a mantle which has melt-rich and melt-poor regions?

4. Response of newly formed lithosphere to fracture mechanics (crack interaction)?

5. Because they can?

The community would benefit from a synthesis of these ideas, pros and cons, evidence for and against each, and an assessment of what further work needs to be done.  Integration of current work on segmentation by Montesi, Carbotte, Toomey, Gregg, Hooft, White, Mutter, Rubin, Salters, Haymon and others would be most interesting and useful.