Science is Fun Fridays!

 Biscuit Basin Boardwalk in Yellowstone National Park following a hydrothermal explosion.

On July 23rd, it's been determined that water suddenly transitioned to steam in the shallow hydrothermal system beneath Black Diamond Pool.  Debris was then shot hundreds of feet above the ground, with grapefruit sized rocks being thrown tens to hundreds of feet from the source.

This was not caused by any volcanic activity.  Seismicity and emissions remain at their normal background level.

But here, you can see the surprise.

This did alter the shape of the pool, and in the after image you can see some murky overflow.

The basin will be closed for the remainder of the season for maintenance and monitoring.