MAGELLAN PROJECT OFFICE

P-38173
5/01/91


     This image, centered at 21.5 degrees north, 359.5 degrees east
is part of an F-MIDR (Full-resolution Mosaicked Image Data Record)
covering Magellan orbits 492-523.  This is a close look at Gula
Mons, a shield volcano 4 kilometers (13100 feet) in height in
northwestern Eistla Regio on Venus.  This type of volcanism is
similar to that of the Hawaiian islands in that it is thought have
resulted from hot material rising from the interior and heating the
crust.  Both volcanoes formed from hot, fluid lava which erupted
non-explosively.  The radar-bright area consists of both the summit
(circular southwestern part) and radial troughs and scarps trending
to the northeast down the slope of Gula Mons.  Evidence of regional
expansion of the crust is expressed in this area by the radial
troughs or graben and a larger scale fracture complex which trends
southeast from the bottom right corner of the image.  The very thin
lineations which extend outward from the summit before bending
southward are thought to be the surface expression of a dike system
(planes of solidified molten rock within bedrock).  The dikes
formed between intermittent outflows of lava which descend from the
summit of Gula Mons. This is apparent from the observation that
some dikes cut the flows while others are covered by them.


Jet Propulsion Laboratory
California Institute of Technology
National Aeronautics and Space Administration
Pasadena, Calif. 91109
ration
Pasadena, Calif. 91109