Travel Reference
In-Depth Information
Black Dragon's Caldron (1986)
Mud Volcano*
is reached by boardwalk today, but in 1870, when the Washburn explor-
ation party named it, there was only a steep hillside. Those who climbed the hill saw a cone
from which mud splashed into the trees as much as 100 feet up and 200 feet away (30 and 60
m), making a tremendous racket. Only two years later, Superintendent Langford returned to
find that “the loud detonations which resembled the discharges of a gun-boat mortar were no
longer heard, and the upper part of the crater and cone had in a great measure disappeared,
leaving a shapeless and unsightly hole much larger than the former crater…” Today, Mud Vol-
cano's dark gray water continues to bubble and churn inside a deep hole at the base of the
hillside.
Acid Hot Springs
The Mud Volcano area and Norris Geyser Basin are the two easily accessible thermal
basins that have great concentrations of acid hot springs. Sulphur Caldron, across the road
and just north of here, has water that is more acidic than lemon juice (with a pH of 1.3). So
much acid and sulfur in the water prevent the growth of multicolored bacteria and algae
seen elsewhere.
Can you believe that anything can live in such an environment? Surprisingly, at least
one microbe
(Sulfolobus acidocaldarius)
thrives here and actually feeds upon sulfur com-
pounds such as hydrogen sulfide. It oxidizes the sulfur, turning it into sulfuric acid.
Formerly classified as a bacterium,
Sulfolobus
is now known to belong to Archaea, a differ-
ent domain of very old organisms. It is quite content in Yellowstone, growing well even at
the amazingly high temperature of 194°F (90°C). These acidic pools and soils also harbor
a more complex organism, a type of alga
(Cyanidium caldarium)
that grows only in acid
conditions and lives at temperatures up to 133°F (57°C).
