The spatial relationship within fields of shield volcanoes and how they compare on the Earth, Venus and the Moon
Shockey, Kelly Michelle
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I investigated the spatial distributions of volcanic vents within fields of shield volcanoes on the Moon and Venus and compared them to the spatial distributions of fields of monogenic basaltic shield volcanoes on Earth. I chose the terrestrial fields (Springerville Volcanic Field, AZ; Snake River Plain, ID; and San Francisco Peaks Volcanic Field, AZ) because these are well studied and well constrained volcanic fields. All three of these fields have known alignments and/or faults that drive the distribution of the vent locations. I investigated the only known volcanic fields on the Moon: the Marius Hills, Gruithuisen Domes, and Rümker Hills. On the surface of Venus, shield fields are the most abundant type of volcanic feature. In selecting 4 of these fields (0°N 216°E, 2°N 315°E, 8°N 79°E, and 78°S 43°E), I considered the overall size of the field (<200 km diameter); the availability of both left-look and right-look Magellan radar data; and location: the examined fields are found in polar and equatorial regions. I used a nearest-neighbor analysis to determine if the individual shields within a single field have a spatial distribution that is indistinguishable from a random (Poisson) distribution. The individual volcanic constructs within the 3 fields on the Moon are indistinguishable from a Poisson nearest-neighbor distribution. On Venus, 3 of the fields investigated here have distributions that are not consistent with a Poisson nearest-neighbor distribution. This suggests that there may be fundamental differences in the evolution of these volcanic fields on the separate planets. On the Moon, I interpret the results to be consistent with the presence of multiple magma sources that drive the genesis of an individual field. In contrast, on Venus, the driving processes are considered to be consistent with a single magmatic source feeding all the shield volcanoes within a single field.