In a National Geographic article, researchers say the magma under Yellow National Park, is even bigger than before.

The latest scans of the super volcanic plume under Yellowstone, measured electrical conductivity, and is described as being like a giant medical CT scan.

Scientists now say the super volcanic plume extends 643km (400 miles), that’s increased from the 241km (150 miles) detected in 2009.  Back then scientist predicted that the plume was actually larger, and the new scanning technique proved them correct.

They also discovered that hot, salty water surrounds and is mixed in with the plume.