Travel Reference
In-Depth Information
If you're walking beside the crater on a cool day, engulfed in steam next to the walls' great
drop-off, you may have a feeling of being at the edge of the earth. No photograph can capture
that sensation.
If you take the boardwalk to the right when it forks, you'll first encounter
Turquoise Pool,
which greatly resembles the semiprecious stone. The color is caused by light reflecting from
minute particles suspended in its water. Grand Prismatic Spring drains into Turquoise, and
Excelsior may have an underground connection with it as well. Sometimes the water drains
nearly out of sight, but it slowly returns in subsequent months.
Next along the path is
Opal Pool,
which got its name from the opalescence both of its wa-
ter and its surrounding sinter. Opal is actually a geyser with rare but sometimes high erup-
tions. Opal sometimes drains its 43-foot-deep (13 m) pool completely, as it did during 2005-7.
Midway Geyser Basin's stellar attraction is
Grand Prismatic Spring [GEO.20].
The largest
hot spring in the park, it measures about 250 by 350 feet (75 by 100 m). Prismatic means “bril-
liantly colored.” The central water in the spring is a brilliant blue, with blue-green near the
edges. Radiating out from this are rays of yellow, orange, and brown— the runoff channels.
Since early days, visitors have remarked about the beautiful reflection of the pool's colors in
the steam.
It's difficult to get a good photo of a spring as huge as Grand Prismatic. Some of the best
are taken from the air, but if you are determined to reach a good viewpoint, there's a choice of
two hills you might climb. East of the main road there's Midway Bluff, and to the southwest of
Grand Prismatic is a burned-over hill skirted by the Fairy Falls Trail (described at mile 11.3/
5.7).
