venus

[wolram]

{incorrect link deleted by Phobos - - see Andre's link}

fantastic picture of venus, showing lava flows.

[russ_watters]

Radar photos - gawd, I love technology.

[Andre]

http://antwrp.gsfc.nasa.gov/apod/ap040323.html

Lavaflows on Venus are several thousend miles long and fill big lakes. This is even more remarkable if we take into consideration that the Planet's surface is much shallower than Earth forming immense plains with little elevation differences. Consequently, to form lava flows that long, the lava must have been liquid for dozens if not hundreds of years.

Of course, as the surface temperature of Venus is up (~740 K) you can expect that lava flows on Venus are less viscuous and cool much slower than on Earth. However with typical lava temperatures of 1300K the difference is big enough for the lava to cool rather quickly (days to months). A case can be made for the dense atmosphere (90-92 bar) acting as an insulation blanket. However counteracting this is that the increased pressure also increases the solidifying temperature.

All in all, with all those vulcanoes and all that lava, it would not be far fetched to assume that the whole of Venus was a very big stove, producing an incredible amount of heat from the inside out, that has been much hotter in the past, at the time when these vulcanoes were active.

But why? I have attempted to explain that in this thread (http://www.physicsforums.com/showthread.php?t=2974).