JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109
 
PHOTO CAPTION                                MAGELLAN
                                             P-37787  MGN-35
                                             3/5/91
 
 
     This Magellan image shows part of the northern boundary of
Ovda Regio, one of the large highlands ringing the equator of
Venus.  The scene consists largely of low-relief, rounded linear
ridges.  These ridges, 8-15 kilometers (5-9 miles) in width and
30-60 kilometers (20-40 miles) long, lie mostly along a 100-200
kilometer (60-120 mile) wide slope where the elevation drops 3
kilometers (2 miles) from Ovda Regio to the surrounding plains. 
Some of the ridges have been cut at right angles by extension
fractures.  Dark material, either lava or windblown dirt, fills the
region between the ridges.  The curvilinear, banded nature of these
ridges suggests that crustal shortening, roughly oriented
north-south, is largely responsible for their formation.  Such
crustal shortening was unexpected by Magellan scientists, who
believed that Ovda Regio, a likely site of hot upwelling from the
interior of Venus, should be dominated by volcanism and crustal
extension.  This image, centered approximately at 1 N 81 E,
measures 300 kilometers (190 miles) by 225 kilometers (140 miles)
and was acquired by Magellan in November 1990.