The most detailed seismic images yet published of the Yellowstone supervolcano’s plumbing shows a plume of hot and molten rock rising from the northwest at a depth of at least 410 miles, contradicting claims that there is no deep plume. A related study indicates the banana-shaped magma chamber a few miles beneath Yellowstone is 20 percent larger than believed, so a future cataclysmic eruption could be larger than thought.