The move used by all the rap video dancers. Done by standing in place and shaking your ass rapidly.
Yo! Dat girls doing that ass volcano on weezy!
An ass volcano is the act of inserting baking powder, vinegar and red food coloring to a gaping asshole (normal it has been stretched out from a vigorous session of anal sex). Once the ingredients have been inserted you will have a grade 7 caliber explosion that even an all taco bell diet can not top.
Did you hear about that piece of whore trash Justin rammed the other night ? I hear he rammed her right in the ass and gave the cum dumpster a fucking ass volcano. I would makke the whore my wife.