Mid-ocean ridges have many characteristics that differentiate them from other areas of volcanic activity. They contain transform faults cutting across them. They are made of basalt that has a distinct geochemical signature. The crust is young closer to the top of the ridge than farther away (because of the rifting and new crust that is forming). The sediments are thinner near the top than farther away from the center of the ridge system. There is a magnetic anomaly across the mid-ocean ridges which forms a "mirror image" pattern indicative of rifting and the formation of new crust.