The_____________ of a portion of a lithospheric plate determines its final elevation. I can't find an answer.
Since this is not my area of expertise, I searched Google under the key words "lithospheric plate elevation" to get these possible sources:
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http://en.wikipedia.org/wiki/Tectonic_plate
http://72.14.253.104/search?q=cache:sn2_3so5Vn0J:bullard.esc.cam.ac.uk/~keith/Publications/KoizumiRP1997_bssa.pdf+lithospheric+plate+elevation&hl=en&gl=us&ct=clnk&cd=3&client=safari
http://72.14.253.104/search?q=cache:HKPaXx1qjPsJ:www.cosis.net/abstracts/EGU06/07623/EGU06-J-07623.pdf+lithospheric+plate+elevation&hl=en&gl=us&ct=clnk&cd=6&client=safari
http://interactive2.usgs.gov/learningweb/teachers/volcanoes_guide_glossary.htm
http://serc.carleton.edu/ess_vocab/part3.htm
I hope this helps. Thanks for asking.