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Divergent plate boundaries are also regions characterised by high topography.  The average elevation of Mid-Oceanic Ridges (MORs) is pretty much constant at about 3600 m below sea level (buoyant level of the asthenosphere).  The oceanic floor has an average elevation of about 5000 m below sea level.  Therefore, MORs are oceanic mountain belts.  Isostasy acting on a thin (or non existing) oceanic lithosphere explains the high topography of MORs.

East Pacific Rise forms as the Pacific and Cocos plates separate at a "fast" rate of 120 millimeters per year. Here a map depicts a 1000 km stretch of the Rise, extending from 8-17°N. The map reveals two kinds of discontinuities: large offsets, about 100 km long, known as transform faults and smaller offsets, about 10 km long, called overlapping spreading centers (detail on the right). Colors indicate depths of from 2350 (pink) to 3500 meters (dark blue).
More at: http://magic.geol.ucsb.edu/~ken/sciam.html

 

Computer-generated detailed topographic map of a segment of the Mid-Oceanic Ridge of the East Pacific Rise. "Warm" colors (yellow to red) indicate the ridge rising above the seafloor, and the "cool" colors (green to blue) represent lower elevations. This image (at latitude 9° north) is of a small part of the East Pacific Rise. The discontinuity in the middle of the picture is called an overlapping spreading center. (Imagery of Stacey Tighe, University of Rhode Island.) 
More at http://pubs.usgs.gov/publications/text/topomap.html