Mid-ocean ridges (MORs)
Stand 2.5-4 km above abyssal plains, and may be ~1000 km across
Axial valleys are 600 m – 2 km lower than ridge mountains
Axial valley/ridge mountains abut oceanic fracture zones
Numerous volcanoes have quiescent eruptions
Axial valleys & ridge mountains composed of basalts in distinctive pillow forms