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Pool of boiling water that formed a few days after the June 13, 2026, hydrothermal explosion at Biscuit Basin, Yellowstone National Park, and that is located near the middle vent group of features that formed during the explosion.  The pool is about 6.5 × 5.3 meters (21 × 17 feet) in size and formed via collapse based on the lack of surrounding ejecta.

Aerial view of the Black Diamond Pool area of Biscuit Basin, Yellowstone National Park, showing the locations of northern, middle, and southern vent groups that formed as a result of a small hydrothermal explosion on June 13, 2026.  The "new pool' developed later, between June 14 and 16.

Looking south, toward Black Diamond Pool (steaming blue area in the left middle ground) along a fissure that formed during a small hydrothermal explosion on June 13, 2026, in Biscuit Basin, Yellowstone National Park.  The fissure is about 18.5 meters (61 feet) long and filled with near-boiling water.

Looking downstream along the Firehole River, Yellowstone National Park, from the Midway Geyser bridge on the morning of June 13, 2026.  The milky colors are due to suspended sediment that flowed into the river as a result of a small hydrothermal explosion at Biscuit Basin, which is located a straight-line distance of about 5 kilometers (3.1 miles) upstream.

Screen capture showing the view from the Biscuit Basin research and monitoring camera at 05:09:54 a.m. MDT on June 13, 2026.  Black Diamond Pool is in the foreground, and a steam plume in the upper right marks the occurrence of a small hydrothermal explosion behind (to the north of) the pool.

Hand sample and outcrop photos of Sour Creek dome ash flow (ignimbrite) packages. (A) Package 1 as clasts (see arrow) within lithic breccia in Bog Creek (Wilson et al., 2018). (B) Package 2 with scoria indicated by arrows. (C) Package 3 with increased crystal sizes to all other packages found within dark matrix.