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Among the most unusual volcanic features observed on Venus are these circular, flat-topped volcanic domes, called pancake domes. This group of pancake domes is called Carmenta Farra. The largest of these domes is 65 kilometers across and roughly 1 kilometer high. A small crater near the center of each dome may have been the source vent for the lava. The center of the largest dome appears to be depressed below the elevation of the margin of the dome. This may be due to partial withdrawal of magma shortly after the eruption. The unusual morphology of these volcanos suggests that they may have a composition different from that of shield volcanos on Venus. On Earth, thick lava flows and domes are usually associated with lavas that are relatively sticky or viscous. These lavas also tend to be richer in silica than basalt, such as dacite or rhyolite. Whether this is true on Venus as well is not known. These domes could also be explained by the eruption of basalt at unusually slow rates. The bright spot at upper right is the 12-kilometer-wide impact crater Margarita. It is bowl-shaped, although a small mound is visible at bottom. The bright material surrounding the crater is blocky ejecta, while the dark material may be due to effects of the impact blast or to finer debris, which appears dark at radar wavelengths. Magellan image
CI-MIDR 15N009. Right
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