#avoca spring

Yellowstone National Park, WY (No. 17)

Shell Spring or Shell Geyser is a depression with built up, rounded, yellow, solidified sinter with a small pool at the center that may be reminiscent of a shell. Hard sinter forms a defined feature area before soft sinter and vegetation begins. Shell Geyser eruptions are cyclical, with an active phase that slowly fills the pool area of the feature, a final long eruption when water is overflowing, then the pool drains and remains quiet for several hours. Cycles can occur over hours to days. High activity prevented conductivity measurements.

Shell Spring has an average temperate of 196.5°F (91.4°C) and an average pH of 8.5.

Yellowstone National Park, WY (No. 15)

A clear deep pool, West Geyser has a minimal sinter rim, but soft and fractured sinter surrounding the pool. Looking into the pool, old branches are visible at the bottom, now covered and white from silica precipitation. The slight sinter shelf along the edge of the pool with shallow water has a rim of yellow/orange thermophiles. West Geyser erupted after the 1959 earthquake, but were not directly observed—only evidence of the water erupting or splashing. There were eruptions in the 1980s, but only overflowing of the pool has occurred since.

West Geyser has an average temperate of 159.1°F (70.6°C), an average pH of 7.9, and an average conductivity of 2171 uS/cm.

Yellowstone National Park, WY (No. 16)

Avoca Spring is a linear, elongated pool that continuously boils with built-up, solidified sinter above the water level. Some of the surrounding area with runoff water is home to orange-colored thermophiles. Avoca Spring has steady boiling and overflowing activity, but no defined eruptions. Earthquakes have a history of altering this continuous activity, with periods of dormancy, and seems to be directly related to Silver Globe Geyser activity.

Avoca Spring has an average temperate of 193.7°F (89.8°C), an average pH of 8.3, and an average conductivity of 2287 uS/cm.

Hot Springs

Hot springs are the most common hydrothermal features in Yellowstone. Their plumbing has no constrictions.

Superheated water cools as it reaches the surface, sinks, and is replaced by hotter water from below.

This circulation prevents water from reaching the temperature needed to set off an eruption.