What If You Dumped an Iceberg Into a Volcano?

In a matter of days, a nearby volcano will erupt, spewing debris and lava, and decimating your city. You know that fighting fire with fire usually makes things worse, but maybe you could fight fire with ice. What happens when lava suddenly cools down? How much ice would you need? Does adding ice to a volcanic eruption make it better or worse? Would an iceberg stop the volcanic eruption? What is sublimation? How does tephra form? Would Mount Michael be the ideal place to put an iceberg into a volcano?