If the massive supervolcano at Yellowstone National Park erupted again, scientists believe it would blanket much of the United States in ash and potentially sever communication as well as travel between the country’s coasts.

According to a new study published by the US Geological Survey, cities about 300 miles away from the volcano’s location in Wyoming would be covered in up to three feet of ash as a result of a supereruption, the largest kind of volcanic eruption possible.