Word: lavas
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...areas that are remarkably free of craters. That would be easy to explain on a planet like Earth, where cratering from meteor strikes is erased by steady erosion. But while there is some evidence of wind erosion on Venus, the best explanation for the lack of cratering is periodic lava flows. Magellan has found direct evidence of such flows, including domelike upwellings and hardened streams of rock trailing down the sides of Venusian peaks. There are also signs of other geologic activity, including dramatic faulting and several distinct episodes of mountain building. But until last week the evidence didn...
This intriguing fact, say project scientists, is a strong hint that the mountain has recently been covered with lava. Rock that sits on the surface of mountaintops appears to weather quickly in the hot, chemically reactive atmosphere, creating a soil that is rich in iron sulfide. It is this mineral, the scientists believe, that shows up easily on radar. If Maat Mons doesn't have any, it has presumably been resurfaced, perhaps within the past few years...
...which indicate that molten rock, called magma, is coming up from deep inside the earth. The magma rises gradually, opening fissures that serve as its pipelines to the surface. What happens next depends on the composition of the magma. If it is fairly liquid, it generally produces a stately lava flow that poses more of a threat to property than to humans. Hawaiian volcanoes tend to follow this pattern...
...Venusian volcanoes are still capable of erupting, and there is even a chance they may be caught in the act. After finishing a 243-day mapping mission, Magellan will start all over and do it again. Any change in the landscape that shows up in the second version -- new lava or other debris, for example -- would be strong evidence of volcanism, making Venus only the fourth body in the solar system, after Earth, Jupiter's moon Io and Neptune's moon Triton, where eruptions have been spotted...
After a balky start, the Magellan probe is mapping the cloud-shrouded planet by radar. Found so far: giant craters, major lava flows and a webwork of faults...