How many active volcanoes do we know of that exists on other planetary bodies?

rocky Mike Clark

Mike,

When we look at all the solid planets and moons in the solar system we see that only two geologic landforms are common: volcanoes and impact craters. Planets and moons whose surfaces are older than about 3 billion years usually have more impact craters than volcanoes and lava flows; younger surfaces usually have more volcanism. The two youngest surfaces are probably the Earth and Jupiter's moon, Io. On both of these bodies there are volcanoes erupting nearly all the time. Io seems to be covered with volcanic materials everywhere. On Earth the ocean floors are volcanic rocks and of course we have many volcanoes on land too.

I don't think I can, however, specifically answer your question. I'm not sure anyone has counted all the volcanoes on any planet! One problem is what is a volcano to be counted? Sometimes volcanoes occur in clusters that may contain hundreds of small cinder cones. Would you count each cone separately? I would count the entire volcanic field as a single volcano. Let me try to guess how many volcanoes there are on several planets. I will just consider larger volcanoes such as stratovolcanoes or shield volcanoes or volcanic fields:
    PLANET OR MOON	     ESTIMATED NUMBER OF BIG VOLCANOES
	Mercury				zero to tens
	Venus			        few thousand
	Earth				ten thousand or so	 
	Moon				zero to a few
	Mars				18 (somebody did count these!)
	Io				hundreds to thousands
	Other Jupiter moons		zero to a few
	Titan (Saturn) 			?, but I guess many
	Triton (Neptune)		a few?
There could be a long description explaining each of these numbers, but instead I will just say that these are my best guesses, based on many years of studying volcanoes in the solar system.

Chuck Wood, University of North Dakota 

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