Hydrothermal explosion versus phreatic eruption?

[Astronuc]

A small hydrothermal explosion occurred in Yellowstone National Park today (July 23, 2024) around 10:00 AM MST in the Biscuit Basin thermal area, about 2.1 miles (3.5 km) northwest of Old Faithful. Numerous videos of the event were recorded by visitors. The boardwalk was damaged, but there were no reports of injury. The explosion appears to have originated near Black Diamond Pool.

Biscuit Basin, including the parking lot and boardwalks, are temporary closed for visitor safety. The Grand Loop road remains open. Yellowstone National Park geologists are investigating the event.

https://www.kron4.com/news/national...t-yellowstone-causes-temporary-shutdown-usgs/
https://dailymontanan.com/2024/07/2...-damage-in-area-of-yellowstone-national-park/

If that's small, I wonder what is considered 'big'

"Yellowstone National Park geologists are investigating the explosion but say data shows no out-of-the-ordinary volcanic activity."

Yellowstone National Park geologists are investigating the explosion but say data shows no out-of-the-ordinary volcanic activity.

Hydrothermal explosions often send boiling water, steam, mud and rock into the air and can reach heights of up to 1.2 miles, according to the U.S. Geological Survey. It said in a 2018 report that large hydrothermal explosions happen on average every 700 years. At least 25 craters have been identified in the park that are at least 328 feet wide, according to the report.

Now the difference:

Phreatic and hydrothermal eruptions are explosive phenomena ubiquitous to volcanoes, calderas and tectonic rifts areas (Browne and Lawless 2001). Phreatic eruptions are produced by explosive expansion of groundwater due to the sudden arrival of heat and gas from intruding magma (or magmatic fluids), whereas hydrothermal eruptions result from the flashing and expansion of hydrothermal water without the need for any magmatic input (Mastin 1995; Browne and Lawless 2001; Thiéry and Mercury 2009). Despite their comparatively small size, these eruptions can be deadly as they often lack precursors (Barberi et al. 1992; Hurst et al. 2014; Stix and de Moor 2018).

https://link.springer.com/article/10.1007/s00445-022-01571-7


Edit/Update: https://www.msn.com/en-us/weather/t...othermal-explosion-in-yellowstone/vi-BB1qxUEr
Section of park is closed. I don't understand why some tourists start walking back towards the location where the explosion occurred.

 

[berkeman]

Section of park is closed.

Edit/Update: https://www.msn.com/en-us/weather/t...othermal-explosion-in-yellowstone/vi-BB1qxUEr

I'm very glad that nobody was hurt. It looks from the aftermath like there could have easily been some injuries from falling rocks and debris.

I don't understand why some tourists start walking back towards the location where the explosion occurred.

I think they were told there would be an award of some sort if they went back to where the explosion took place. Some kind of Darwin Award or similar...

 

[gmax137]

I've seen tourists in Yellowstone try to pet the wild Buffalo. So, trying to get a closer look at the crater is totally expected.

 

[Astronuc]

This spring, geologists discovered a small crater at Norris Geyser Basin that, based on monitoring data, appears to have formed during a minor hydrothermal explosion on April 15, 2024.
https://www.usgs.gov/observatories/yvo/news/a-small-hydrothermal-explosion-norris-geyser-basin

The Norris Geyser Basin in about 25 miles (40 km) NNE from Biscuit Basin, which is about 2.1 miles (3.5 km) NNW of 'Old Faithful' geyser site. "The closest seismometer to Biscuit Basin is at Old Faithful and it did not register any changes due to the explosion."
Ref: https://www.kbzk.com/news/local-new...basin-not-uncommon-says-top-volcano-scientist

Mike Polland describes meter sized rocks propelled out of the Black Diamond Pool (another source mentions Sapphire Pool) in Biscuit Basin, and smaller rocks 100s of feet away.

https://www.facebook.com/share/v/xq8DFGmUzMpa6VFT/


https://www.msn.com/en-us/weather/t...ermal-explosion-s-cause-explained/ar-BB1qxK9i

 

[G Bonn]

A bigger past explosion made Indian Pond just north of Yellowstone Lake. I've hiked the storm point trail that runs by it. You wouldn't want to be near something that big exploding.

https://www.researchgate.net/figure...meters-in-maximum-diameter-and_fig1_312913163

The publication link on the above page seems to work, but I didn't read it.

 

[Nik_2213]

As I understand it, a hydrothermal eruption is a 'dirty geyser', but a phreatic may generate a shallow crater of considerable extent, known as a maar...
IMHO, you can probably out-run former's 'fall-out', but latter is more a 'Be Not There' event.

Note a flood meeting caldera's shallow magma may blow orders of magnitude more violently than for mere ground-water, per Hunga-Tonga, Krakatoa, Santorini / Thera, possibly Toba...