Black Diamond Pool’s Extraordinary Eruption

Jul 26, 2024

On Tuesday, July 23, 2024, Black Diamond Pool in Yellowstone’s Biscuit Basin exploded in an exceptionally large eruption – the largest seen to date. In this article, we’ll explore the thermal feature’s historic behavior and look ahead to see what might happen next.

 

Location & History

Black Diamond Pool is located in the Upper Geyser Basin in the smaller area known as Biscuit Basin. Near it are other pools, one named Black Opal Pool and the other Wall Pool. Another pool that remains unnamed is also in the area.

 

The photo below shows my understanding of how we currently refer to these thermal features.
This area has been active with explosive eruptions of black, muddy water since at least 1918. This thermal feature likely broke out sometime between 1905 and 1912, but wasn’t named until an active phase in 1934 when the name Black Diamond was first used in a report. Thermal Features are named for how they look, behave or where they’re located.

 

“Black Boulder Geyser,” another name for neighboring Black Opal Pool, was used in the same 1934 report. That name makes perfect sense in light of the recent eruption. This area has seen black, muddy eruptions that toss many rocks throughout the years.

 

In more recent times, Black Diamond reactivated in 2006 and has been seen intermittently since. Eruptions have ranged from 30 to 100 feet in height and lasted only a minute or less, with just one or two bursts. When a geyser starts in an active phase, eruptions are often more frequent. In 2006, Black Diamond had smaller eruptions through July that only had hours or a day between them. Then, the time between eruptions lengthened. Witnesses have mentioned that it starts with little warning.

 

In fact, in 2009, Park Geologist Henry Heasler was touring Biscuit Basin with a group of researchers when they experienced a “walk-up” eruption of Black Diamond.

In 2011, the NPS workers inadvertently swapped the signs for Wall Pool and Black Diamond Pool, so some reports of eruptions that have come in since then may be listed as Wall Pool but were likely Black Diamond. Hopefully, the correct signage will be added when a decision is made regarding the placement of the boardwalk. Or perhaps Wall Pool no longer exists, and the distinction is no longer an issue.

Eruption or Hydrothermal Explosion?

Geologists are classifying the recent eruption as a Hydrothermal Explosion and not just an eruption. While I’ve not seen a definitive definition to date, the difference seems to lie in whether the eruption significantly alters the crater instead of erupting only from the existing crater.

By comparing aerial photos and those on the ground, there was a slight expansion of the edge farthest from the boardwalk and perhaps to the “left” – though we won’t know more until the water clears or geologists or the NPS releases more reports.

July 2024 Eruption

 
The incredibly powerful eruption seen on July 23, 2024, reached heights of 300 feet or more. It is incredible that nobody was hurt and that the videos of the eruption exist from quick-thinking visitors and guides to the park. We may learn from these a better-estimated height.
 
The amount of debris tossed out was astounding.

An eruption of that magnitude may have blown out the plumbing system, and it could take years for the geyser to repair. But then again, being so full of mud, Black Diamond may take less time to repair any damage.

As a comparison, we can look to Excelsior (near Grand Prismatic Spring at Midway Geyser Basin), which had powerfully explosive eruptions that broke apart its plumbing in the late 1800s. The next observed eruptions were smaller and lasted only a few days in 1985. That’s a long recovery time. But Excelsior does not have the mud to help seal up cracks in the plumbing and relies on the slow deposition of minerals to seal things up.

For now, though, Biscuit Basin is closed for the rest of the summer season – as is prudent, given the amount of damage. Time will tell whether it blew out its plumbing or if Black Diamond will treat us to more powerful eruptions. We’ll know more in the coming days and weeks.

Get to Know the Geysers

To learn more about geysers, head over to Yellowstone Naturalist to learn more in a series of articles.

You can also see a small portion of my 19-year passion project of repeat photography of the thermal features in Yellowstone. I’m endlessly fascinated by the thermal energy shifts in geyser basins. This photo project helps document the changes.

Janet Jones
Owner, Publisher, Editor

Janet has a rich history in Cody with her grandparents moving here in the late 1930s. Her grandfather started Wyoming Well Service. Janet is a writer, photographer, graphic designer and webmaster. Cody Journal and Cody Calendar blends her skills and talents with her love of the area.

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