Mid-ocean ridges (MORs)
Stand 2.5-4 km above abyssal plains, and may be ~1000 km across
Characterized by high relief; steep-sided axial valleys or troughs are 600 m – 2 km lower than adjacent ridge mountains
In plan, straight sections of axial valley/ridge mountains abut against oceanic fracture zones
Axial valleys and ridge mountains dotted by active volcanoes that erupt often, with a quiescent eruption style
Axial valleys and ridge mountains composed of volcanic rock - basalts in distinctive pillow forms