plain of lateral planation

plain of lateral planation

[′plān əv ¦lad·ə·rəl plā′nā·shən]
(geology)
An extensive, smooth, apronlike surface developed at the base of a mountain or escarpment by the widening of valleys and the coalescence of floodplains as a result of lateral planation.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.