I wasn't aware that the moon had volcanoes?
At one time, the moon’s craters were all attributed to volcanism. That was laid to rest as a consequence of the Apollo mission astronauts who sampled, examined, and photographed the lunar surface. The volcanic explanation made some sense, but was basically an alibi against impact. The so-called “Late Heavy Bombardment” is ascribed to a 200 million year period beginning 4 billion years ago, putting it waaaay back in time, and farrrrr, farrrrr away from our own.
Scientists unearth ancient impact’s secrets
A giant meteorite struck Earth 1.8 billion years ago, creating Sudbury Basin.
What does this event tell us about early Earth?
by Mark Jirsa (December issue)
http://www.astronomy.com/asy/default.aspx?c=i&id=462