What would happen if the Yellowstone supervolcano actually erupted?

If the supervolcano underneath Yellowstone National Park ever had another massive eruption, it could spew ash for thousands of miles across the United States, damaging buildings, smothering crops, and shutting down power plants. It'd be a huge disaster.  






Read More: http://news.yahoo.com/happen-yellowstone-supervolcano-actually-erupted-150700226.html