Established in 1872, Yellowstone is the oldest national park in the
United States (and in the world). Everything we have come to associate
with national parks was first developed there, so for many people
Yellowstone is what comes to mind when they think of a national park.
After all, Hanna-Barbera set their Yogi Bear cartoons in “Jellystone”
Park. The stereotype is perhaps appropriate, as Yellowstone has
everything you’d expect.
Its 8,987 square kilometers include forests, rivers, 290 waterfalls,
abundant wildlife, unspoiled views, plus a unique assortment of over
10,000 geothermal features.
Yellowstone’s location in western Wyoming (with small sections
spilling over into Montana and Idaho) makes it the quintessential summer
road trip destination for over two million visitors each year. Families
from around the country can escape urban traffic jams to sit in their
mini-vans and SUVs enjoying nature— while jammed bumper to bumper
with all the other families’ mini-vans and SUVs. Unfortunately,
congestion is now a major part of the “experience” when visiting any of
the popular national parks in the summer.
According to the story frequently repeated in guidebooks, both the park
and the Yellowstone river that begins within its boundaries got their
names from the colorful Grand Canyon of the Yellowstone.
Like the famous Grand Canyon in Arizona, this one is the result of a
river cutting through layers of rock. The canyon is 275 meters deep in
some places, and 800 meters wide. Before the river eroded it, the
volcanic rock was part of a geyser basin. Boiling mineral-rich water
permeated it with yellow iron compounds. The name is a free translation
of the French Roches Jaunes— “Yellowstone” sounds better
than “Yellowrocks.” The French fur trappers who “discovered” Yellowstone
translated that from Mi-Tsi-A-Da-Zi, which they thought was its
Hidatsa Indian name. Historians now believe it actually referred to some
yellow bluffs near Billings, Montana.
I visited Yellowstone in late May, which many guidebook authors consider
one of the best times to go there. The summer traffic jams haven’t yet
arrived, and snow (usually) has given way to greenery. But unpredictable
weather can make an off-season visit risky. The date the snow plows open
the park’s roads varies each year; had I arrived a week earlier the
park would have been inaccessible. Although the roads were open, snow
was still on the ground and the sky was overcast enough of the time to
make photography challenging.
Yellowstone is in the caldera of the largest volcano in North America.
An enormous eruption 640,000 years ago— possibly 1,000 times
larger than the one at Mount St. Helens in 1980— created the giant
crater, 85 kilometers long and 45 kilometers wide. Although another
cataclysmic eruption doesn’t seem imminent, the “hot spot” deep in the
Earth’s mantle keeps the groundwater boiling. As it bubbles, seeps, or
explodes to the surface, the hot water creates the diverse collection of
pools, mud pots, fumaroles, and geysers for which Yellowstone is
renowned.
Geysers are the most flamboyant of Yellowstone’s geothermal features.
The largest ones can shoot boiling water tens of meters into the air.
Old Faithful is the park’s (and the world’s) most famous geyser. Among
geysers it’s neither the largest, the most active, nor the most
explosive; but it reliably erupts 23 times a day with a plume 30 to 55
meters high. There’s a popular myth that Old Faithful erupts on the
hour. It actually erupts every 70 to 80 minutes on the average, though
the intervals can vary from 33 minutes to two hours. Rangers can predict
the time of the next eruption based on the duration of the previous one.
Yellowstone’s colorful pools have quieter personalities. They collect
near-boiling water that lacks sufficient pressure to erupt as geysers.
Thermophilic (“heat-loving”) microbes thrive in water so hot and
sulfurous that it would quickly kill other organisms. The species that
enjoy the hottest temperatures bask inside the pools, painting them dark
blue, green, or yellow. Others grow in bright orange mats along the
cooler edges of a pool. Wooden boardwalks along the pools prevent
visitors from ruining the fragile ecosystem, and also prevent the
scalding water from ruining fragile visitors.
Pools come in sizes to fit all tastes. Grand Prismatic Spring (above
left) is the largest, 113 meters across. I don’t know which pool is the
smallest, but a number of petite pools are actually geysers. A geyser
can become a dormant pool when changes to the underground “plumbing” reduce
its water supply. But some active geysers look like pools when they’re
not erupting.
Opalescent Pool is the runoff from a geyser that began erupting in the
1950s. It’s cooler than a typical hot water pool, and really should be
called a pond. The water inundated and killed a stand of lodgepole
pines. Dissolved minerals in the water deposited a crust of white silica
on the bottom of the dead trees and stumps. It’s in Black Sands Basin,
named for the fragments of obsidian, a glass formed in explosive
volcanic eruptions.
Mammoth Hot Springs is an alien landscape worthy of a science fiction
movie set. The hot water there percolates through porous limestone, so
it seeps and bubbles to the surface as “springs” rather than collecting
in pools or building up pressure to make geysers.
Volcanic carbon dioxide gas becomes carbonic acid in water, forming a
seltzer that dissolves the alkaline limestone. The result of this
chemistry experiment is a buildup of travertine as the water
flows and evaporates. Travertine is calcium carbonate, the protean
ingredient of limestone, eggshells, Tums, pearls, and marble. It’s a
process similar to the formation of stalagmites in caves, or the tufa
formations at Mono Lake in
California. Although the travertine is white when it first precipitates,
bacteria and algae soon colonize it where the water flows, painting it
pink, orange, and brown.
A spring can sculpt eerie formations as the travertine precipitates and
dissolves in the hot water and rain, forcing the spring’s water to flow
in new directions. Sometimes the buildup completely clogs the outlet,
drying up the spring and its microbial population. It may also form
terraces. As water collects in pools and then overflows, it
creates a “stone waterfall” with tiered layers of pools.
A trail circles Minerva Terrace, the largest and most ornate of the
travertine formations. A menagerie of thermophilic organisms paint the
terraces in shades of pink, brown, and orange. Standing at the bottom of
the terrace on a “partly cloudy” day, you can easily imagine an
elaborate stairway ascending into the heavens.
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