JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109

PHOTO CAPTION                                MAGELLAN
                                             P-37125  MGN-18
                                             11/16/90


     This image of the eastern edge of Alpha Regio, 30 degrees
south latitude, 11.8 east longitude, was acquired on November 7,
1990.  It shows seven circular domical hills averaging 25
kilometers (15 miles) in diameter and maximum heights of 750 meters
(2475 feet).  These features can be interpreted as viscous or thick
eruptions of lava coming from a vent on the relatively level ground
allowing the lava to flow in an even lateral pattern.  The
concentric and radial fracture pattern on their surfaces suggests
if they are extrusive that a chilled outer layer formed then
further intrusion in the interior stretched the surface.  The domes
may be analogous to volcanic domes on Earth.  An alternative
interpretation is that the domes are the result of shallow
intrusions up-doming the surface layers.  If they are intrusive,
then magma withdrawal near the end of the eruptions then produced
the fractures.  The bright margins possibly indicate the presence
of rock debris or talus at the slopes of the domes.  Fractures on
the surrounding plains are both older and younger than the domical
hills.  Resolution of the Magellan data is about 120 meters (400
feet).